First commit

75 files changed, 5975 insertions, 0 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 0000000..b4713dc
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,46 @@
+# nanowasm, a tiny WebAssembly/Wasm interpreter
+# Copyright (C) 2023-2024  Xavier Del Campo Romero
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+cmake_minimum_required(VERSION 3.19)
+project(nanowasm C)
+option(NW_LOG "Enables logging to stderr" ON)
+add_library(${PROJECT_NAME})
+target_include_directories(${PROJECT_NAME} PUBLIC include
+    PRIVATE private_include)
+
+set(cflags_np
+    -ffunction-sections
+    -fdata-sections
+    -pedantic
+    -Wall
+    -std=c99
+)
+
+if(CMAKE_BUILD_TYPE STREQUAL "Debug")
+    set(cflags_np ${cflags_np} -Og)
+elseif(CMAKE_BUILD_TYPE STREQUAL "Release")
+    set(cflags_np ${cflags_np} -Os)
+endif()
+
+include(CheckCompilerFlag)
+
+foreach(f ${cflags_np})
+    string(REPLACE "-" "_" var supported_${f})
+    check_compiler_flag(C ${f} ${var})
+
+    if(${var})
+        target_compile_options(${PROJECT_NAME} PRIVATE ${f})
+    endif()
+endforeach()
+
+if(NW_LOG)
+    target_compile_definitions(${PROJECT_NAME} PRIVATE ENABLE_LOG)
+endif()
+
+set_target_properties(${PROJECT_NAME} PROPERTIES C_STANDARD 99 C_EXTENSIONS OFF)
+add_subdirectory(src)
+add_subdirectory(test)
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..d0a1fa1
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,373 @@
+Mozilla Public License Version 2.0
+==================================
+
+1. Definitions
+--------------
+
+1.1. "Contributor"
+    means each individual or legal entity that creates, contributes to
+    the creation of, or owns Covered Software.
+
+1.2. "Contributor Version"
+    means the combination of the Contributions of others (if any) used
+    by a Contributor and that particular Contributor's Contribution.
+
+1.3. "Contribution"
+    means Covered Software of a particular Contributor.
+
+1.4. "Covered Software"
+    means Source Code Form to which the initial Contributor has attached
+    the notice in Exhibit A, the Executable Form of such Source Code
+    Form, and Modifications of such Source Code Form, in each case
+    including portions thereof.
+
+1.5. "Incompatible With Secondary Licenses"
+    means
+
+    (a) that the initial Contributor has attached the notice described
+        in Exhibit B to the Covered Software; or
+
+    (b) that the Covered Software was made available under the terms of
+        version 1.1 or earlier of the License, but not also under the
+        terms of a Secondary License.
+
+1.6. "Executable Form"
+    means any form of the work other than Source Code Form.
+
+1.7. "Larger Work"
+    means a work that combines Covered Software with other material, in
+    a separate file or files, that is not Covered Software.
+
+1.8. "License"
+    means this document.
+
+1.9. "Licensable"
+    means having the right to grant, to the maximum extent possible,
+    whether at the time of the initial grant or subsequently, any and
+    all of the rights conveyed by this License.
+
+1.10. "Modifications"
+    means any of the following:
+
+    (a) any file in Source Code Form that results from an addition to,
+        deletion from, or modification of the contents of Covered
+        Software; or
+
+    (b) any new file in Source Code Form that contains any Covered
+        Software.
+
+1.11. "Patent Claims" of a Contributor
+    means any patent claim(s), including without limitation, method,
+    process, and apparatus claims, in any patent Licensable by such
+    Contributor that would be infringed, but for the grant of the
+    License, by the making, using, selling, offering for sale, having
+    made, import, or transfer of either its Contributions or its
+    Contributor Version.
+
+1.12. "Secondary License"
+    means either the GNU General Public License, Version 2.0, the GNU
+    Lesser General Public License, Version 2.1, the GNU Affero General
+    Public License, Version 3.0, or any later versions of those
+    licenses.
+
+1.13. "Source Code Form"
+    means the form of the work preferred for making modifications.
+
+1.14. "You" (or "Your")
+    means an individual or a legal entity exercising rights under this
+    License. For legal entities, "You" includes any entity that
+    controls, is controlled by, or is under common control with You. For
+    purposes of this definition, "control" means (a) the power, direct
+    or indirect, to cause the direction or management of such entity,
+    whether by contract or otherwise, or (b) ownership of more than
+    fifty percent (50%) of the outstanding shares or beneficial
+    ownership of such entity.
+
+2. License Grants and Conditions
+--------------------------------
+
+2.1. Grants
+
+Each Contributor hereby grants You a world-wide, royalty-free,
+non-exclusive license:
+
+(a) under intellectual property rights (other than patent or trademark)
+    Licensable by such Contributor to use, reproduce, make available,
+    modify, display, perform, distribute, and otherwise exploit its
+    Contributions, either on an unmodified basis, with Modifications, or
+    as part of a Larger Work; and
+
+(b) under Patent Claims of such Contributor to make, use, sell, offer
+    for sale, have made, import, and otherwise transfer either its
+    Contributions or its Contributor Version.
+
+2.2. Effective Date
+
+The licenses granted in Section 2.1 with respect to any Contribution
+become effective for each Contribution on the date the Contributor first
+distributes such Contribution.
+
+2.3. Limitations on Grant Scope
+
+The licenses granted in this Section 2 are the only rights granted under
+this License. No additional rights or licenses will be implied from the
+distribution or licensing of Covered Software under this License.
+Notwithstanding Section 2.1(b) above, no patent license is granted by a
+Contributor:
+
+(a) for any code that a Contributor has removed from Covered Software;
+    or
+
+(b) for infringements caused by: (i) Your and any other third party's
+    modifications of Covered Software, or (ii) the combination of its
+    Contributions with other software (except as part of its Contributor
+    Version); or
+
+(c) under Patent Claims infringed by Covered Software in the absence of
+    its Contributions.
+
+This License does not grant any rights in the trademarks, service marks,
+or logos of any Contributor (except as may be necessary to comply with
+the notice requirements in Section 3.4).
+
+2.4. Subsequent Licenses
+
+No Contributor makes additional grants as a result of Your choice to
+distribute the Covered Software under a subsequent version of this
+License (see Section 10.2) or under the terms of a Secondary License (if
+permitted under the terms of Section 3.3).
+
+2.5. Representation
+
+Each Contributor represents that the Contributor believes its
+Contributions are its original creation(s) or it has sufficient rights
+to grant the rights to its Contributions conveyed by this License.
+
+2.6. Fair Use
+
+This License is not intended to limit any rights You have under
+applicable copyright doctrines of fair use, fair dealing, or other
+equivalents.
+
+2.7. Conditions
+
+Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the licenses granted
+in Section 2.1.
+
+3. Responsibilities
+-------------------
+
+3.1. Distribution of Source Form
+
+All distribution of Covered Software in Source Code Form, including any
+Modifications that You create or to which You contribute, must be under
+the terms of this License. You must inform recipients that the Source
+Code Form of the Covered Software is governed by the terms of this
+License, and how they can obtain a copy of this License. You may not
+attempt to alter or restrict the recipients' rights in the Source Code
+Form.
+
+3.2. Distribution of Executable Form
+
+If You distribute Covered Software in Executable Form then:
+
+(a) such Covered Software must also be made available in Source Code
+    Form, as described in Section 3.1, and You must inform recipients of
+    the Executable Form how they can obtain a copy of such Source Code
+    Form by reasonable means in a timely manner, at a charge no more
+    than the cost of distribution to the recipient; and
+
+(b) You may distribute such Executable Form under the terms of this
+    License, or sublicense it under different terms, provided that the
+    license for the Executable Form does not attempt to limit or alter
+    the recipients' rights in the Source Code Form under this License.
+
+3.3. Distribution of a Larger Work
+
+You may create and distribute a Larger Work under terms of Your choice,
+provided that You also comply with the requirements of this License for
+the Covered Software. If the Larger Work is a combination of Covered
+Software with a work governed by one or more Secondary Licenses, and the
+Covered Software is not Incompatible With Secondary Licenses, this
+License permits You to additionally distribute such Covered Software
+under the terms of such Secondary License(s), so that the recipient of
+the Larger Work may, at their option, further distribute the Covered
+Software under the terms of either this License or such Secondary
+License(s).
+
+3.4. Notices
+
+You may not remove or alter the substance of any license notices
+(including copyright notices, patent notices, disclaimers of warranty,
+or limitations of liability) contained within the Source Code Form of
+the Covered Software, except that You may alter any license notices to
+the extent required to remedy known factual inaccuracies.
+
+3.5. Application of Additional Terms
+
+You may choose to offer, and to charge a fee for, warranty, support,
+indemnity or liability obligations to one or more recipients of Covered
+Software. However, You may do so only on Your own behalf, and not on
+behalf of any Contributor. You must make it absolutely clear that any
+such warranty, support, indemnity, or liability obligation is offered by
+You alone, and You hereby agree to indemnify every Contributor for any
+liability incurred by such Contributor as a result of warranty, support,
+indemnity or liability terms You offer. You may include additional
+disclaimers of warranty and limitations of liability specific to any
+jurisdiction.
+
+4. Inability to Comply Due to Statute or Regulation
+---------------------------------------------------
+
+If it is impossible for You to comply with any of the terms of this
+License with respect to some or all of the Covered Software due to
+statute, judicial order, or regulation then You must: (a) comply with
+the terms of this License to the maximum extent possible; and (b)
+describe the limitations and the code they affect. Such description must
+be placed in a text file included with all distributions of the Covered
+Software under this License. Except to the extent prohibited by statute
+or regulation, such description must be sufficiently detailed for a
+recipient of ordinary skill to be able to understand it.
+
+5. Termination
+--------------
+
+5.1. The rights granted under this License will terminate automatically
+if You fail to comply with any of its terms. However, if You become
+compliant, then the rights granted under this License from a particular
+Contributor are reinstated (a) provisionally, unless and until such
+Contributor explicitly and finally terminates Your grants, and (b) on an
+ongoing basis, if such Contributor fails to notify You of the
+non-compliance by some reasonable means prior to 60 days after You have
+come back into compliance. Moreover, Your grants from a particular
+Contributor are reinstated on an ongoing basis if such Contributor
+notifies You of the non-compliance by some reasonable means, this is the
+first time You have received notice of non-compliance with this License
+from such Contributor, and You become compliant prior to 30 days after
+Your receipt of the notice.
+
+5.2. If You initiate litigation against any entity by asserting a patent
+infringement claim (excluding declaratory judgment actions,
+counter-claims, and cross-claims) alleging that a Contributor Version
+directly or indirectly infringes any patent, then the rights granted to
+You by any and all Contributors for the Covered Software under Section
+2.1 of this License shall terminate.
+
+5.3. In the event of termination under Sections 5.1 or 5.2 above, all
+end user license agreements (excluding distributors and resellers) which
+have been validly granted by You or Your distributors under this License
+prior to termination shall survive termination.
+
+************************************************************************
+*                                                                      *
+*  6. Disclaimer of Warranty                                           *
+*  -------------------------                                           *
+*                                                                      *
+*  Covered Software is provided under this License on an "as is"       *
+*  basis, without warranty of any kind, either expressed, implied, or  *
+*  statutory, including, without limitation, warranties that the       *
+*  Covered Software is free of defects, merchantable, fit for a        *
+*  particular purpose or non-infringing. The entire risk as to the     *
+*  quality and performance of the Covered Software is with You.        *
+*  Should any Covered Software prove defective in any respect, You     *
+*  (not any Contributor) assume the cost of any necessary servicing,   *
+*  repair, or correction. This disclaimer of warranty constitutes an   *
+*  essential part of this License. No use of any Covered Software is   *
+*  authorized under this License except under this disclaimer.         *
+*                                                                      *
+************************************************************************
+
+************************************************************************
+*                                                                      *
+*  7. Limitation of Liability                                          *
+*  --------------------------                                          *
+*                                                                      *
+*  Under no circumstances and under no legal theory, whether tort      *
+*  (including negligence), contract, or otherwise, shall any           *
+*  Contributor, or anyone who distributes Covered Software as          *
+*  permitted above, be liable to You for any direct, indirect,         *
+*  special, incidental, or consequential damages of any character      *
+*  including, without limitation, damages for lost profits, loss of    *
+*  goodwill, work stoppage, computer failure or malfunction, or any    *
+*  and all other commercial damages or losses, even if such party      *
+*  shall have been informed of the possibility of such damages. This   *
+*  limitation of liability shall not apply to liability for death or   *
+*  personal injury resulting from such party's negligence to the       *
+*  extent applicable law prohibits such limitation. Some               *
+*  jurisdictions do not allow the exclusion or limitation of           *
+*  incidental or consequential damages, so this exclusion and          *
+*  limitation may not apply to You.                                    *
+*                                                                      *
+************************************************************************
+
+8. Litigation
+-------------
+
+Any litigation relating to this License may be brought only in the
+courts of a jurisdiction where the defendant maintains its principal
+place of business and such litigation shall be governed by laws of that
+jurisdiction, without reference to its conflict-of-law provisions.
+Nothing in this Section shall prevent a party's ability to bring
+cross-claims or counter-claims.
+
+9. Miscellaneous
+----------------
+
+This License represents the complete agreement concerning the subject
+matter hereof. If any provision of this License is held to be
+unenforceable, such provision shall be reformed only to the extent
+necessary to make it enforceable. Any law or regulation which provides
+that the language of a contract shall be construed against the drafter
+shall not be used to construe this License against a Contributor.
+
+10. Versions of the License
+---------------------------
+
+10.1. New Versions
+
+Mozilla Foundation is the license steward. Except as provided in Section
+10.3, no one other than the license steward has the right to modify or
+publish new versions of this License. Each version will be given a
+distinguishing version number.
+
+10.2. Effect of New Versions
+
+You may distribute the Covered Software under the terms of the version
+of the License under which You originally received the Covered Software,
+or under the terms of any subsequent version published by the license
+steward.
+
+10.3. Modified Versions
+
+If you create software not governed by this License, and you want to
+create a new license for such software, you may create and use a
+modified version of this License if you rename the license and remove
+any references to the name of the license steward (except to note that
+such modified license differs from this License).
+
+10.4. Distributing Source Code Form that is Incompatible With Secondary
+Licenses
+
+If You choose to distribute Source Code Form that is Incompatible With
+Secondary Licenses under the terms of this version of the License, the
+notice described in Exhibit B of this License must be attached.
+
+Exhibit A - Source Code Form License Notice
+-------------------------------------------
+
+  This Source Code Form is subject to the terms of the Mozilla Public
+  License, v. 2.0. If a copy of the MPL was not distributed with this
+  file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+If it is not possible or desirable to put the notice in a particular
+file, then You may include the notice in a location (such as a LICENSE
+file in a relevant directory) where a recipient would be likely to look
+for such a notice.
+
+You may add additional accurate notices of copyright ownership.
+
+Exhibit B - "Incompatible With Secondary Licenses" Notice
+---------------------------------------------------------
+
+  This Source Code Form is "Incompatible With Secondary Licenses", as
+  defined by the Mozilla Public License, v. 2.0.
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..a18be97
--- /dev/null
+++ b/README.md
@@ -0,0 +1,29 @@
+# `nanowasm`, a tiny WebAssembly/Wasm interpreter
+
+**This project is still unfinished and is not meant for production use.**
+
+This project aims to provide the most minimal Wasm interpreter possible in
+strictly portable ISO C99.
+
+## Features
+
+- Portable, ISO C99 implementation
+- Suitable for resource-constrained devices.
+- Does not require dynamic memory allocation.
+
+## What `nanowasm` is not
+
+As opposed to other interpreters, `nanowasm` prefers lower memory usage
+rather than run-time performance. Therefore, it should not be unfairly
+compared _performance_-wise against other interpreters.
+
+## License
+
+```
+nanowasm, a tiny WebAssembly/Wasm interpreter
+Copyright (C) 2023-2024  Xavier Del Campo Romero
+
+This Source Code Form is subject to the terms of the Mozilla Public
+License, v. 2.0. If a copy of the MPL was not distributed with this
+file, You can obtain one at https://mozilla.org/MPL/2.0/.
+```
diff --git a/include/nanowasm/nw.h b/include/nanowasm/nw.h
new file mode 100644
index 0000000..2cdb8a4
--- /dev/null
+++ b/include/nanowasm/nw.h
@@ -0,0 +1,29 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef NANOWASM_H
+#define NANOWASM_H
+
+#include <nanowasm/types.h>
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+int nw_load(const struct nw_mod_cfg *cfg, struct nw_mod *m);
+int nw_start(const struct nw_inst_cfg *icfg, struct nw_inst *i);
+enum nw_state nw_run(struct nw_inst *i);
+int nw_stop(struct nw_inst *i);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/include/nanowasm/types.h b/include/nanowasm/types.h
new file mode 100644
index 0000000..637dd31
--- /dev/null
+++ b/include/nanowasm/types.h
@@ -0,0 +1,144 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef NANOWASM_TYPES_H
+#define NANOWASM_TYPES_H
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+union nw_value
+{
+    long i32;
+    long long i64;
+    float f32;
+    double f64;
+    /* TODO: define {de}serialization between Wasm and host. */
+    void *p;
+};
+
+enum nw_kind
+{
+    NW_KIND_FUNCTION,
+    NW_KIND_TABLE,
+    NW_KIND_MEMORY,
+    NW_KIND_GLOBAL
+};
+
+struct nw_args
+{
+    const union nw_value *args;
+    size_t n;
+};
+
+struct nw_buf
+{
+    void *buf;
+    size_t n;
+};
+
+enum nw_state
+{
+    NW_STATE_AGAIN,
+    NW_STATE_RETURNED,
+    NW_STATE_EXCEPTION,
+    NW_STATE_FATAL
+};
+
+struct nw_mod_cfg
+{
+    const struct nw_import
+    {
+        enum nw_kind kind;
+        const char *module, *field;
+
+        union
+        {
+            struct
+            {
+                /* This must follow the format below, whitespace ignored:
+                 * [return type]([param type][, ...])
+                 * For convenience, the interpreter can do automatic checks on
+                 * pointer arguments and/or return values if using '*' as type.
+                 * Examples:
+                 * "()"
+                 * "i32(f32)"
+                 * "*(f64, i32, *, i64)"
+                 * As per WebAssembly MVP spec, multiple return types are not
+                 * supported yet. */
+                const char *signature;
+                int (*fn)(const struct nw_args *params,
+                    union nw_value *ret, void *user);
+            } function;
+        } u;
+    } *imports;
+
+    size_t n_imports;
+    const char *path;
+    void *user;
+};
+
+struct nw_interp_cfg
+{
+    struct nw_buf stack, heap, global;
+    const struct nw_mod *m;
+};
+
+struct nw_inst_cfg
+{
+    struct nw_interp_cfg interp;
+};
+
+struct nw_mod
+{
+    struct nw_sections
+    {
+        long type, import, function, table, memory, global, export,
+            start, element, code, data;
+    } sections;
+
+    size_t data_len, heap_len;
+    struct nw_mod_cfg cfg;
+};
+
+struct nw_inst
+{
+    struct nw_interp
+    {
+        const struct nw_mod *m;
+        FILE *f;
+        const char *exception;
+        bool exit;
+        int retval;
+        struct nw_interp_cfg cfg;
+        size_t stack_i, global_i;
+        struct nw_frame *fp;
+        struct nw_gframe *gfp;
+    } interp;
+
+    union nw_inst_state
+    {
+        long retval;
+        const char *exception;
+    } state;
+};
+
+#define NW_BUF(sz) {.buf = (char [sz]){0}, .n = sz}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/private_include/nw/fstring.h b/private_include/nw/fstring.h
new file mode 100644
index 0000000..a8feda4
--- /dev/null
+++ b/private_include/nw/fstring.h
@@ -0,0 +1,18 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef FSTRING_H
+#define FSTRING_H
+
+#include <stdbool.h>
+#include <stdio.h>
+
+int fstrcmp(const char *str, FILE *f, bool abort);
+
+#endif
diff --git a/private_include/nw/interp.h b/private_include/nw/interp.h
new file mode 100644
index 0000000..5fa37bf
--- /dev/null
+++ b/private_include/nw/interp.h
@@ -0,0 +1,39 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INTERP_H
+#define INTERP_H
+
+#include <nanowasm/nw.h>
+#include <nw/opcodes.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+
+struct interp_set
+{
+    const enum opcode *opcodes;
+    size_t n;
+};
+
+extern const struct interp_set interp_initexpr_set;
+
+int interp_start(const struct nw_interp_cfg *cfg, FILE *f, struct nw_interp *i);
+int interp_run(struct nw_interp *i);
+int interp_run_limited(struct nw_interp *i, const struct interp_set *ops);
+int interp_check_opcode(uint8_t op, FILE *f);
+int interp_push(struct nw_interp *i, const struct nw_frame *f);
+int interp_pop(struct nw_interp *i);
+void *interp_stackptr(const struct nw_interp *i);
+int interp_stack_push(struct nw_interp *i, const void *src, size_t n);
+int interp_stack_pop(struct nw_interp *i, void *dst, size_t n);
+int interp_heap_store(struct nw_interp *i, size_t addr, const void *src, size_t n);
+int interp_heap_load(struct nw_interp *i, size_t addr, void *dst, size_t n);
+
+#endif
diff --git a/private_include/nw/leb128.h b/private_include/nw/leb128.h
new file mode 100644
index 0000000..4338255
--- /dev/null
+++ b/private_include/nw/leb128.h
@@ -0,0 +1,18 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef LEB128_H
+#define LEB128_H
+
+#include <stdio.h>
+
+int leb128_read_unsigned(FILE *f, unsigned maxbits, unsigned long long *out);
+int leb128_read_signed(FILE *f, unsigned maxbits, long long *out);
+
+#endif
diff --git a/private_include/nw/log.h b/private_include/nw/log.h
new file mode 100644
index 0000000..3eafc88
--- /dev/null
+++ b/private_include/nw/log.h
@@ -0,0 +1,21 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef LOG_H
+#define LOG_H
+
+#include <stdio.h>
+
+#ifdef ENABLE_LOG
+#define LOG(...) fprintf(stderr, __VA_ARGS__)
+#else
+#define LOG(...)
+#endif
+
+#endif
diff --git a/private_include/nw/opcodes.h b/private_include/nw/opcodes.h
new file mode 100644
index 0000000..2822b0d
--- /dev/null
+++ b/private_include/nw/opcodes.h
@@ -0,0 +1,67 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef OPCODES_H
+#define OPCODES_H
+
+enum opcode
+{
+    OP_UNREACHABLE,
+    OP_NOP,
+    OP_BLOCK,
+    OP_LOOP,
+    OP_IF,
+    OP_ELSE,
+    OP_END = 0xb,
+    OP_BR,
+    OP_BR_IF,
+    OP_BR_TABLE,
+    OP_RETURN = 0xf,
+    OP_CALL,
+    OP_CALL_INDIRECT,
+    OP_DROP = 0x1a,
+    OP_SELECT,
+    OP_GET_LOCAL = 0x20,
+    OP_SET_LOCAL,
+    OP_TEE_LOCAL,
+    OP_GET_GLOBAL,
+    OP_SET_GLOBAL,
+    OP_I32_LOAD = 0x28,
+    OP_I64_LOAD,
+    OP_F32_LOAD,
+    OP_F64_LOAD,
+    OP_I32_LOAD8_S,
+    OP_I32_LOAD8_U,
+    OP_I32_LOAD16_S,
+    OP_I32_LOAD16_U,
+    OP_I64_LOAD8_S,
+    OP_I64_LOAD8_U,
+    OP_I64_LOAD16_S,
+    OP_I64_LOAD16_U,
+    OP_I64_LOAD32_S,
+    OP_I64_LOAD32_U,
+    OP_I32_STORE,
+    OP_I64_STORE,
+    OP_F32_STORE,
+    OP_F64_STORE,
+    OP_I32_STORE8,
+    OP_I32_STORE16,
+    OP_I64_STORE8,
+    OP_I64_STORE16,
+    OP_I64_STORE32,
+    OP_CURRENT_MEMORY,
+    OP_GROW_MEMORY,
+    OP_I32_CONST,
+    OP_I64_CONST,
+    OP_F32_CONST,
+    OP_F64_CONST,
+    OP_I32_SUB = 0x6b
+};
+
+#endif
diff --git a/private_include/nw/ops.h b/private_include/nw/ops.h
new file mode 100644
index 0000000..02f191e
--- /dev/null
+++ b/private_include/nw/ops.h
@@ -0,0 +1,69 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef OPS_H
+#define OPS_H
+
+#include <nanowasm/nw.h>
+#include <stdio.h>
+
+int op_unreachable(struct nw_interp *i);
+int op_nop(struct nw_interp *i);
+int op_block(struct nw_interp *i);
+int op_loop(struct nw_interp *i);
+int op_if(struct nw_interp *i);
+int op_else(struct nw_interp *i);
+int op_end(struct nw_interp *i);
+int op_br(struct nw_interp *i);
+int op_br_if(struct nw_interp *i);
+int op_br_table(struct nw_interp *i);
+int op_return(struct nw_interp *i);
+int op_call(struct nw_interp *i);
+int op_call_indirect(struct nw_interp *i);
+int op_get_local(struct nw_interp *i);
+int op_set_local(struct nw_interp *i);
+int op_tee_local(struct nw_interp *i);
+int op_get_global(struct nw_interp *i);
+int op_set_global(struct nw_interp *i);
+int op_i32_load(struct nw_interp *i);
+int op_i32_store(struct nw_interp *i);
+int op_current_memory(struct nw_interp *i);
+int op_i32_const(struct nw_interp *i);
+int op_i64_const(struct nw_interp *i);
+int op_f32_const(struct nw_interp *i);
+int op_f64_const(struct nw_interp *i);
+int op_i32_sub(struct nw_interp *i);
+
+int check_unreachable(FILE *f);
+int check_nop(FILE *f);
+int check_block(FILE *f);
+int check_loop(FILE *f);
+int check_if(FILE *f);
+int check_else(FILE *f);
+int check_end(FILE *f);
+int check_br(FILE *f);
+int check_br_if(FILE *f);
+int check_br_table(FILE *f);
+int check_return(FILE *f);
+int check_call(FILE *f);
+int check_call_indirect(FILE *f);
+int check_get_local(FILE *f);
+int check_set_local(FILE *f);
+int check_tee_local(FILE *f);
+int check_get_global(FILE *f);
+int check_set_global(FILE *f);
+int check_i32_load(FILE *f);
+int check_i32_store(FILE *f);
+int check_i32_const(FILE *f);
+int check_i64_const(FILE *f);
+int check_f32_const(FILE *f);
+int check_f64_const(FILE *f);
+int check_i32_sub(FILE *f);
+
+#endif
diff --git a/private_include/nw/search.h b/private_include/nw/search.h
new file mode 100644
index 0000000..937e6fd
--- /dev/null
+++ b/private_include/nw/search.h
@@ -0,0 +1,29 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef SEARCH_H
+#define SEARCH_H
+
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <stdio.h>
+
+struct search_fn
+{
+    long start;
+    bool returns;
+    varuint32 index;
+};
+
+int search_exported_fn(const char *fn, const struct nw_mod *m, FILE *f,
+    struct search_fn *out);
+int search_fn(varuint32 index, const struct nw_mod *m, FILE *f,
+    struct search_fn *out);
+
+#endif
diff --git a/private_include/nw/sections.h b/private_include/nw/sections.h
new file mode 100644
index 0000000..bef9cd8
--- /dev/null
+++ b/private_include/nw/sections.h
@@ -0,0 +1,65 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef SECTIONS_H
+#define SECTIONS_H
+
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <stddef.h>
+#include <stdio.h>
+
+struct section
+{
+    const struct nw_mod_cfg *cfg;
+    FILE *f;
+};
+
+int section_custom_check(const struct section *s, struct nw_mod *m, unsigned long len);
+int section_type_check(const struct section *s, struct nw_mod *m, unsigned long len);
+int section_import_check(const struct section *s, struct nw_mod *m, unsigned long len);
+int section_function_check(const struct section *s, struct nw_mod *m, unsigned long len);
+int section_table_check(const struct section *s, struct nw_mod *m, unsigned long len);
+int section_memory_check(const struct section *s, struct nw_mod *m, unsigned long len);
+int section_global_check(const struct section *s, struct nw_mod *m, unsigned long len);
+int section_export_check(const struct section *s, struct nw_mod *m, unsigned long len);
+int section_start_check(const struct section *s, struct nw_mod *m, unsigned long len);
+int section_element_check(const struct section *s, struct nw_mod *m, unsigned long len);
+int section_code_check(const struct section *s, struct nw_mod *m, unsigned long len);
+int section_data_check(const struct section *s, struct nw_mod *m, unsigned long len);
+
+struct section_function
+{
+    varuint32 type, index, nreturn;
+};
+
+struct section_code
+{
+    long start;
+};
+
+int section_function(const struct section *s, const struct nw_mod *m,
+    varuint32 idx, struct section_function *f);
+int section_code(const struct section *s, const struct nw_mod *m,
+    varuint32 idx, struct section_code *c);
+
+int section_code_push(FILE *f, long pc, struct nw_frame *fr);
+int section_type_push(FILE *f, const struct nw_mod *m, varuint32 idx,
+        struct nw_frame *fr);
+int section_global_push(FILE *f, const struct nw_mod *m, struct nw_interp *i);
+
+struct resizable_limits
+{
+    bool max_available;
+    size_t sz, max;
+};
+
+int check_resizable_limits(FILE *f, struct resizable_limits *r);
+
+#endif
diff --git a/private_include/nw/types.h b/private_include/nw/types.h
new file mode 100644
index 0000000..23a2306
--- /dev/null
+++ b/private_include/nw/types.h
@@ -0,0 +1,81 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef WASM_TYPES_H
+#define WASM_TYPES_H
+
+#include <nanowasm/nw.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+
+typedef bool varuint1;
+typedef signed char varint7;
+typedef unsigned char varuint7;
+typedef unsigned long varuint32;
+typedef long varint32;
+typedef unsigned long long varuint64;
+typedef long long varint64;
+
+#define VALUE_TYPES \
+    X(VALUE_TYPE_I32) \
+    X(VALUE_TYPE_I64) \
+    X(VALUE_TYPE_F32) \
+    X(VALUE_TYPE_F64)
+
+enum value_type
+{
+#define X(x) x,
+    VALUE_TYPES
+#undef X
+};
+
+struct retval
+{
+    bool returns;
+    enum value_type type;
+};
+
+struct nw_block
+{
+    long pc;
+    struct nw_block *prev;
+};
+
+struct nw_frame
+{
+    enum value_type local_type;
+    unsigned long n_locals;
+    struct retval retval;
+    struct nw_block *last_block;
+    struct nw_frame *prev, *next;
+};
+
+struct nw_gframe
+{
+    enum value_type type;
+    bool mutable;
+    struct nw_gframe *next;
+};
+
+int varuint1_read(FILE *f, varuint1 *out);
+int varint7_read(FILE *f, varint7 *out);
+int varuint7_read(FILE *f, varuint7 *out);
+int varuint32_read(FILE *f, varuint32 *out);
+int varint32_read(FILE *f, varint32 *out);
+int varuint64_read(FILE *f, varuint64 *out);
+int varint64_read(FILE *f, varint64 *out);
+
+int get_value_type(varint7 type, enum value_type *vtype);
+size_t get_type_size(enum value_type type);
+
+int32_t htoni32(int32_t in);
+const char *value_type_tostr(enum value_type v);
+
+#endif
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
new file mode 100644
index 0000000..77be1e5
--- /dev/null
+++ b/src/CMakeLists.txt
@@ -0,0 +1,20 @@
+# nanowasm, a tiny WebAssembly/Wasm interpreter
+# Copyright (C) 2023-2024  Xavier Del Campo Romero
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+target_sources(${PROJECT_NAME} PRIVATE
+    fstrcmp.c
+    interp.c
+    leb128.c
+    load.c
+    run.c
+    search.c
+    start.c
+    stop.c
+    types.c
+)
+add_subdirectory(op)
+add_subdirectory(section)
diff --git a/src/fstrcmp.c b/src/fstrcmp.c
new file mode 100644
index 0000000..b26baa8
--- /dev/null
+++ b/src/fstrcmp.c
@@ -0,0 +1,41 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/fstring.h>
+#include <nw/log.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+int fstrcmp(const char *str, FILE *const f, const bool abort)
+{
+    int ret = 0;
+
+    for (size_t i = 0; i < strlen(str); i++)
+    {
+        uint8_t byte;
+
+        if (!fread(&byte, sizeof byte, 1, f))
+        {
+            LOG("%s: fread(3) failed, feof=%d, ferror=%d\n",
+                __func__, feof(f), ferror(f));
+            return -1;
+        }
+        else if (byte != str[i])
+        {
+            if (abort)
+                return -1;
+            else
+                ret = -1;
+        }
+    }
+
+    return ret;
+}
diff --git a/src/interp.c b/src/interp.c
new file mode 100644
index 0000000..3a32df0
--- /dev/null
+++ b/src/interp.c
@@ -0,0 +1,516 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nanowasm/nw.h>
+#include <nw/log.h>
+#include <nw/interp.h>
+#include <nw/opcodes.h>
+#include <nw/ops.h>
+#include <nw/sections.h>
+#include <nw/types.h>
+#include <errno.h>
+#include <limits.h>
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static const enum opcode initexpr_opcodes[] =
+{
+    OP_NOP,
+    OP_END,
+    OP_I32_CONST,
+    OP_I64_CONST,
+    OP_F32_CONST,
+    OP_F64_CONST
+};
+
+const struct interp_set interp_initexpr_set =
+{
+    .opcodes = initexpr_opcodes,
+    .n = sizeof initexpr_opcodes / sizeof *initexpr_opcodes
+};
+
+static int (*const ops[])(struct nw_interp *) =
+{
+    [OP_UNREACHABLE] = op_unreachable,
+    [OP_NOP] = op_nop,
+    [OP_BLOCK] = op_block,
+    [OP_LOOP] = op_loop,
+    [OP_IF] = op_if,
+    [OP_ELSE] = op_else,
+    [OP_END] = op_end,
+    [OP_BR] = op_br,
+    [OP_BR_IF] = op_br_if,
+    [OP_BR_TABLE] = op_br_table,
+    [OP_RETURN] = op_return,
+    [OP_CALL] = op_call,
+    [OP_CALL_INDIRECT] = op_call_indirect,
+    [OP_GET_LOCAL] = op_get_local,
+    [OP_SET_LOCAL] = op_set_local,
+    [OP_TEE_LOCAL] = op_tee_local,
+    [OP_GET_GLOBAL] = op_get_global,
+    [OP_SET_GLOBAL] = op_set_global,
+    [OP_I32_LOAD] = op_i32_load,
+    [OP_I32_STORE] = op_i32_store,
+    [OP_I32_CONST] = op_i32_const,
+    [OP_I64_CONST] = op_i64_const,
+    [OP_F32_CONST] = op_f32_const,
+    [OP_F64_CONST] = op_f64_const,
+    [OP_I32_SUB] = op_i32_sub
+};
+
+int interp_run(struct nw_interp *const i)
+{
+    uint8_t op;
+
+    if (!fread(&op, sizeof op, 1, i->f))
+    {
+        LOG("%s: fread(3) failed, feof=%d, ferror=%d\n", __func__, feof(i->f),
+            ferror(i->f));
+        i->exception = "I/O error";
+        return -1;
+    }
+    else if (op >= sizeof ops / sizeof *ops)
+    {
+        LOG("%s: invalid opcode %#" PRIx8 "\n", __func__, op);
+        i->exception = "invalid opcode";
+        return -1;
+    }
+    else if (!ops[op])
+    {
+        LOG("%s: unsupported opcode %#" PRIx8 "\n", __func__, op);
+        i->exception = "invalid opcode";
+        return -1;
+    }
+
+    return ops[op](i);
+}
+
+static int run_opcode_limited(struct nw_interp *const in,
+    const struct interp_set *const set)
+{
+    uint8_t op;
+
+    if (!fread(&op, sizeof op, 1, in->f))
+    {
+        LOG("%s: fread(3) failed, feof=%d, ferror=%d\n",
+            __func__, feof(in->f), ferror(in->f));
+        in->exception = "I/O error";
+        return -1;
+    }
+
+    for (size_t i = 0; i < set->n; i++)
+        if (op == set->opcodes[i])
+            return ops[op](in);
+
+    LOG("%s: unexpected opcode %#" PRIx8 "\n", __func__, op);
+    in->exception = "invalid opcode";
+    return -1;
+}
+
+int interp_run_limited(struct nw_interp *const i,
+    const struct interp_set *const set)
+{
+    while (!i->exit)
+        if (run_opcode_limited(i, set))
+        {
+            LOG("%s: run_opcode_limited failed\n", __func__);
+            return -1;
+        }
+
+    return 0;
+}
+
+int interp_check_opcode(const uint8_t op, FILE *const f)
+{
+    static int (*const checks[])(FILE *) =
+    {
+        [OP_UNREACHABLE] = check_unreachable,
+        [OP_NOP] = check_nop,
+        [OP_BLOCK] = check_block,
+        [OP_LOOP] = check_loop,
+        [OP_IF] = check_if,
+        [OP_ELSE] = check_else,
+        [OP_END] = check_end,
+        [OP_BR] = check_br,
+        [OP_BR_IF] = check_br_if,
+        [OP_BR_TABLE] = check_br_table,
+        [OP_RETURN] = check_return,
+        [OP_CALL] = check_call,
+        [OP_CALL_INDIRECT] = check_call_indirect,
+        [OP_GET_LOCAL] = check_get_local,
+        [OP_SET_LOCAL] = check_set_local,
+        [OP_TEE_LOCAL] = check_tee_local,
+        [OP_GET_GLOBAL] = check_get_global,
+        [OP_SET_GLOBAL] = check_set_global,
+        [OP_I32_LOAD] = check_i32_load,
+        [OP_I32_STORE] = check_i32_store,
+        [OP_I32_CONST] = check_i32_const,
+        [OP_I64_CONST] = check_i64_const,
+        [OP_F32_CONST] = check_f32_const,
+        [OP_F64_CONST] = check_f64_const,
+        [OP_I32_SUB] = check_i32_sub
+    };
+
+    if (op >= sizeof checks / sizeof *checks)
+    {
+        LOG("%s: invalid opcode %#" PRIx8 "\n", __func__, op);
+        return 1;
+    }
+    else if (!checks[op])
+    {
+        LOG("%s: unsupported opcode %#" PRIx8 "\n", __func__, op);
+        return 1;
+    }
+
+    return checks[op](f);
+}
+
+int interp_start(const struct nw_interp_cfg *const cfg, FILE *const f,
+    struct nw_interp *const i)
+{
+    *i = (const struct nw_interp)
+    {
+        .f = f,
+        .cfg = *cfg
+    };
+
+    return 0;
+}
+
+void *interp_stackptr(const struct nw_interp *const i)
+{
+    return (char *)i->cfg.stack.buf + i->stack_i;
+}
+
+static int push_frame(struct nw_interp *const i,
+    const struct nw_frame *const src)
+{
+    struct nw_frame *const dst = interp_stackptr(i);
+
+    if (interp_stack_push(i, src, sizeof (*src)))
+    {
+        LOG("%s: interp_stack_push failed\n", __func__);
+        return -1;
+    }
+    else if (i->fp)
+        i->fp->next = dst;
+
+    i->fp = dst;
+    return 0;
+}
+
+static bool mul_overflow(const size_t a, const size_t b)
+{
+    return a && (a * b) / a != b;
+}
+
+static void init_i32(const varuint32 count, void *const p)
+{
+    for (int32_t *i = p; i - (const int32_t *)p < count; i++)
+        *i = 0;
+}
+
+static void init_i64(const varuint32 count, void *const p)
+{
+    for (int64_t *i = p; i - (const int64_t *)p < count; i++)
+        *i = 0;
+}
+
+static void init_f32(const varuint32 count, void *const p)
+{
+    for (float *i = p; i - (const float *)p < count; i++)
+        *i = 0;
+}
+
+static void init_f64(const varuint32 count, void *const p)
+{
+    for (double *i = p; i - (const double *)p < count; i++)
+        *i = 0;
+}
+
+static void init_locals(const enum value_type type, const varuint32 count,
+    void *const p)
+{
+    static void (*const init[])(varuint32, void *) =
+    {
+        [VALUE_TYPE_I32] = init_i32,
+        [VALUE_TYPE_I64] = init_i64,
+        [VALUE_TYPE_F32] = init_f32,
+        [VALUE_TYPE_F64] = init_f64
+    };
+
+    init[type](count, p);
+}
+
+static int push_locals(struct nw_interp *const i,
+    const struct nw_frame *const f)
+{
+    const enum value_type t = f->local_type;
+    const size_t typesz = get_type_size(t);
+    const unsigned long n = f->n_locals;
+
+    if (mul_overflow(typesz, f->n_locals))
+    {
+        LOG("%s: local variables size mul overflow", __func__);
+        i->exception = "mul overfllow";
+        return -1;
+    }
+
+    const size_t totalsz = typesz * n, max = i->cfg.stack.n;
+
+    if (totalsz > max || i->stack_i > max - totalsz)
+    {
+        LOG("%s: cannot allocate locals\n", __func__);
+        i->exception = "stack overflow";
+        return 1;
+    }
+
+    init_locals(t, n, interp_stackptr(i));
+    i->stack_i += totalsz;
+    return 0;
+}
+
+static int do_push_labels(struct nw_interp *const i,
+    const struct nw_frame *const fr)
+{
+    size_t n = 0;
+
+    for (;;)
+    {
+
+        interp_check_opcode();
+    }
+}
+
+static int push_labels(struct nw_interp *const i,
+    const struct nw_frame *const fr)
+{
+    FILE *const f = i->f;
+    const long orig = ftell(f);
+
+    if (orig < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+    else if (do_push_labels(i, fr))
+    {
+        LOG("%s: do_push_labels failed\n", __func__);
+        return -1;
+    }
+    else if (fseek(f, orig, SEEK_SET))
+    {
+        LOG("%s: fseek(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    return -1;
+}
+
+int interp_push(struct nw_interp *const i, const struct nw_frame *const f)
+{
+    if (push_frame(i, f))
+    {
+        LOG("%s: push_frame failed\n", __func__);
+        return -1;
+    }
+    else if (push_locals(i, f))
+    {
+        LOG("%s: push_locals failed\n", __func__);
+        return -1;
+    }
+    else if (push_labels(i, f))
+    {
+        LOG("%s: push_labels failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+struct retval_priv
+{
+    enum value_type type;
+
+    union
+    {
+        int32_t i32;
+        int64_t i64;
+        float f32;
+        double f64;
+    } u;
+};
+
+static void get_i32(const void *const buf, struct retval_priv *const rp)
+{
+    rp->u.i32 = *(((const int32_t *)buf) - 1);
+}
+
+static void get_i64(const void *const buf, struct retval_priv *const rp)
+{
+    rp->u.i64 = *(((const int64_t *)buf) - 1);
+}
+
+static void get_f32(const void *const buf, struct retval_priv *const rp)
+{
+    rp->u.f32 = *(((const float *)buf) - 1);
+}
+
+static void get_f64(const void *const buf, struct retval_priv *const rp)
+{
+    rp->u.f64 = *(((const double *)buf) - 1);
+}
+
+static int get_retval(struct nw_interp *const i,
+    struct retval_priv *const rp)
+{
+    const struct retval *const r = &i->fp->retval;
+    const size_t sz = get_type_size(r->type), max = i->cfg.stack.n;
+
+    if (max < sz || i->stack_i >= max - sz)
+    {
+        static const char exc[] = "stack underflow";
+
+        LOG("%s: %s\n", __func__, exc);
+        i->exception = exc;
+        return -1;
+    }
+
+    const void *const buf = (const char *)interp_stackptr(i) - sz;
+    static void (*const get[])(const void *, struct retval_priv *) =
+    {
+        [VALUE_TYPE_I32] = get_i32,
+        [VALUE_TYPE_I64] = get_i64,
+        [VALUE_TYPE_F32] = get_f32,
+        [VALUE_TYPE_F64] = get_f64
+    };
+
+    get[r->type](buf, rp);
+    rp->type = r->type;
+    i->stack_i -= sz;
+    return 0;
+}
+
+int interp_pop(struct nw_interp *const i)
+{
+    if (!i->fp)
+    {
+        static const char exc[] = "no frame pointer";
+
+        LOG("%s: %s\n", __func__, exc);
+        i->exception = exc;
+        return -1;
+    }
+
+    const struct retval *const r = &i->fp->retval;
+    struct retval_priv rp;
+
+    if (r->returns && get_retval(i, &rp))
+    {
+        LOG("%s: get_retval failed\n", __func__);
+        return -1;
+    }
+
+    const char *const stackptr = interp_stackptr(i);
+    const ptrdiff_t diff = stackptr - (const char *)i->fp;
+
+    i->stack_i -= diff;
+
+    if (!(i->fp = i->fp->prev))
+    {
+        /* Entry point is always assumed to return int, which is
+         * defined as an i32 variable according to Wasm. */
+        if (rp.type != VALUE_TYPE_I32)
+        {
+            LOG("%s: expected i32 return type, got %s\n", __func__,
+                value_type_tostr(rp.type));
+            i->exception = "unexpected return type";
+            return -1;
+        }
+
+        i->retval = rp.u.i32;
+        i->exit = true;
+    }
+
+    return 0;
+}
+
+int interp_stack_push(struct nw_interp *const i, const void *const src,
+    const size_t n)
+{
+    void *const dst = interp_stackptr(i);
+
+    if (i->cfg.stack.n < n || i->stack_i > i->cfg.stack.n - n)
+    {
+        LOG("%s: stack overflow\n", __func__);
+        i->exception = "stack overflow";
+        return -1;
+    }
+
+    memcpy(dst, src, n);
+    i->stack_i += n;
+    return 0;
+}
+
+int interp_stack_pop(struct nw_interp *const i, void *const dst,
+    const size_t n)
+{
+    if (i->stack_i < n)
+    {
+        LOG("%s: stack underflow\n", __func__);
+        i->exception = "stack underflow";
+        return -1;
+    }
+
+    i->stack_i -= n;
+    memcpy(dst, interp_stackptr(i), n);
+    return 0;
+}
+
+int interp_heap_store(struct nw_interp *const i, const size_t addr,
+    const void *const src, const size_t n)
+{
+    if (i->cfg.heap.n < n || addr > i->cfg.heap.n - n)
+    {
+        static const char exc[] = "heap overflow";
+
+        LOG("%s: %s\n", __func__, exc);
+        i->exception = exc;
+        return -1;
+    }
+
+    void *const dst = (char *)i->cfg.heap.buf + addr;
+
+    memcpy(dst, src, n);
+    return 0;
+}
+
+int interp_heap_load(struct nw_interp *const i, const size_t addr,
+    void *const dst, const size_t n)
+{
+    const size_t max = i->cfg.heap.n;
+
+    if (max < n || addr > max - n)
+    {
+        static const char exc[] = "heap out-of-bounds access";
+
+        LOG("%s: %s (%lu, max %zu)\n", __func__, exc, (unsigned long)addr, max);
+        i->exception = exc;
+        return -1;
+    }
+
+    const void *const src = (const char *)i->cfg.heap.buf + addr;
+
+    memcpy(dst, src, n);
+    return 0;
+}
diff --git a/src/leb128.c b/src/leb128.c
new file mode 100644
index 0000000..3c3c8a5
--- /dev/null
+++ b/src/leb128.c
@@ -0,0 +1,71 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/leb128.h>
+#include <nw/log.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+
+/* The functions below are (somewhat heavily) modified versions of those
+ * provided by the wac project: https://github.com/kanaka/wac */
+
+/*
+ * Copyright (C) Joel Martin <github@martintribe.org>
+ * The wac project is licensed under the MPL 2.0 (Mozilla Public License
+ * 2.0). The text of the MPL 2.0 license is included below and can be
+ * found at https://www.mozilla.org/MPL/2.0/
+ */
+
+static int read_LEB(FILE *const f, const unsigned maxbits,
+    const bool sign, unsigned long long *const out)
+{
+    unsigned long long result = 0;
+    unsigned shift = 0, bcnt = 0;
+    uint8_t byte;
+
+    for (;;)
+    {
+        if (!fread(&byte, sizeof byte, 1, f))
+            return -1;
+
+        result |= (unsigned long long)(byte & 0x7f) << shift;
+        shift += 7;
+
+        if (!(byte & 0x80))
+            break;
+        else if (++bcnt > (maxbits + 7 - 1) / 7)
+        {
+            LOG("%s: overflow\n", __func__);
+            return -1;
+        }
+    }
+
+    if (sign && (shift < maxbits) && (byte & 0x40))
+        result |= -1ll << shift;
+
+    *out = result;
+    return 0;
+}
+
+int leb128_read_unsigned(FILE *const f, const unsigned maxbits,
+    unsigned long long *const out)
+{
+    return read_LEB(f, maxbits, false, out);
+}
+
+int leb128_read_signed(FILE *const f, const unsigned maxbits,
+    long long *const out)
+{
+    unsigned long long value;
+    const int ret = read_LEB(f, maxbits, true, &value);
+
+    *out = value;
+    return ret;
+}
diff --git a/src/load.c b/src/load.c
new file mode 100644
index 0000000..2ba0fcc
--- /dev/null
+++ b/src/load.c
@@ -0,0 +1,178 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nanowasm/nw.h>
+#include <nw/sections.h>
+#include <nw/types.h>
+#include <errno.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static int check_magic(FILE *const f)
+{
+    static const uint8_t m[] = {'\0', 'a', 's', 'm'};
+    uint8_t magic[sizeof m];
+
+    if (!fread(magic, sizeof magic, 1, f))
+    {
+        LOG("%s: fread(3) failed, feof=%d, ferror=%d\n",
+            __func__, feof(f), ferror(f));
+        return -1;
+    }
+    else if (memcmp(magic, m, sizeof magic))
+    {
+        LOG("%s: wrong magic bytes\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+static int check_version(FILE *const f)
+{
+    static const uint8_t v[] = {1, 0, 0, 0};
+    uint8_t version[sizeof v];
+
+    if (!fread(version, sizeof version, 1, f))
+    {
+        LOG("%s: fread(3) failed, feof=%d, ferror=%d\n", __func__, feof(f),
+            ferror(f));
+        return -1;
+    }
+    else if (memcmp(version, v, sizeof version))
+    {
+        LOG("%s: wrong version\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+static int load_section(const struct nw_mod_cfg *const cfg,
+    struct nw_mod *const m, FILE *const f)
+{
+    static int (*const fn[])(const struct section *, struct nw_mod *,
+        unsigned long) =
+    {
+        section_custom_check,
+        section_type_check,
+        section_import_check,
+        section_function_check,
+        section_table_check,
+        section_memory_check,
+        section_global_check,
+        section_export_check,
+        section_start_check,
+        section_element_check,
+        section_code_check,
+        section_data_check
+    };
+
+    const struct section s =
+    {
+        .cfg = cfg,
+        .f = f
+    };
+
+    varuint7 section;
+    varuint32 len;
+    int ret;
+
+    if (varuint7_read(f, &section))
+    {
+        if (feof(f))
+            return 0;
+
+        LOG("%s: varuint7_read failed\n", __func__);
+        return 1;
+    }
+    else if (section >= sizeof fn / sizeof *fn)
+    {
+        LOG("%s: invalid section %u\n", __func__, (unsigned)section);
+        return 1;
+    }
+    else if (varuint32_read(f, &len))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return 1;
+    }
+    else if ((ret = fn[section](&s, m, len)))
+        LOG("%s: failed to load section %u\n", __func__, (unsigned)section);
+
+    return ret;
+}
+
+static int load_sections(const struct nw_mod_cfg *const cfg,
+    struct nw_mod *const m, FILE *const f)
+{
+    while (!feof(f))
+        if (load_section(cfg, m, f))
+        {
+            LOG("%s: load_section failed\n", __func__);
+            return -1;
+        }
+
+    return 0;
+}
+
+static int load(const struct nw_mod_cfg *const cfg, struct nw_mod *const m,
+    FILE *const f)
+{
+    if (check_magic(f))
+    {
+        LOG("%s: load_magic failed\n", __func__);
+        return -1;
+    }
+    else if (check_version(f))
+    {
+        LOG("%s: check_version failed\n", __func__);
+        return -1;
+    }
+    else if (load_sections(cfg, m, f))
+    {
+        LOG("%s: load_sections failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+int nw_load(const struct nw_mod_cfg *const cfg, struct nw_mod *const m)
+{
+    int ret = -1;
+    FILE *const f = fopen(cfg->path, "rb");
+
+    *m = (const struct nw_mod){.cfg = *cfg};
+
+    if (!f)
+    {
+        LOG("%s: fopen(3) %s: %s\n", __func__, cfg->path, strerror(errno));
+        goto end;
+    }
+    else if (load(cfg, m, f))
+    {
+        LOG("%s: load failed\n", __func__);
+        goto end;
+    }
+
+    ret = 0;
+
+end:
+    if (f && fclose(f))
+    {
+        LOG("%s: fclose(3) %s: %s\n", __func__, cfg->path, strerror(errno));
+        ret = -1;
+    }
+
+    return ret;
+}
diff --git a/src/op/CMakeLists.txt b/src/op/CMakeLists.txt
new file mode 100644
index 0000000..7bf27de
--- /dev/null
+++ b/src/op/CMakeLists.txt
@@ -0,0 +1,13 @@
+# nanowasm, a tiny WebAssembly/Wasm interpreter
+# Copyright (C) 2023-2024  Xavier Del Campo Romero
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+add_subdirectory(call)
+add_subdirectory(constants)
+add_subdirectory(control_flow)
+add_subdirectory(memory)
+add_subdirectory(numeric)
+add_subdirectory(variable_access)
diff --git a/src/op/call/CMakeLists.txt b/src/op/call/CMakeLists.txt
new file mode 100644
index 0000000..527f35d
--- /dev/null
+++ b/src/op/call/CMakeLists.txt
@@ -0,0 +1,11 @@
+# nanowasm, a tiny WebAssembly/Wasm interpreter
+# Copyright (C) 2023-2024  Xavier Del Campo Romero
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+target_sources(${PROJECT_NAME} PRIVATE
+    call.c
+    call_indirect.c
+)
diff --git a/src/op/call/call.c b/src/op/call/call.c
new file mode 100644
index 0000000..19355ca
--- /dev/null
+++ b/src/op/call/call.c
@@ -0,0 +1,79 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/interp.h>
+#include <nw/search.h>
+#include <nw/sections.h>
+#include <nw/types.h>
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+
+static int call(struct nw_interp *const i, const varuint32 function_index)
+{
+    FILE *const f = i->f;
+    const struct nw_mod *const m = i->cfg.m;
+    struct nw_frame fr = {0};
+    struct search_fn fn;
+
+    /* TODO: treat import functions. */
+    if (search_fn(function_index, m, f, &fn))
+    {
+        LOG("%s: search_fn failed\n", __func__);
+        return -1;
+    }
+    else if (section_type_push(f, m, fn.index, &fr))
+    {
+        LOG("%s: section_type_push failed\n", __func__);
+        return -1;
+    }
+    else if (section_code_push(f, fn.start, &fr))
+    {
+        LOG("%s: section_code_push failed\n", __func__);
+        return -1;
+    }
+    else if (interp_push(i, &fr))
+    {
+        LOG("%s: interp_push failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+static int op(struct nw_interp *const i, FILE *const f)
+{
+    varuint32 function_index;
+
+    if (varuint32_read(f, &function_index))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+    else if (i && call(i, function_index))
+    {
+        LOG("%s: call failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+int op_call(struct nw_interp *const i)
+{
+    return op(i, i->f);
+}
+
+int check_call(FILE *const f)
+{
+    return op(NULL, f);
+}
diff --git a/src/op/call/call_indirect.c b/src/op/call/call_indirect.c
new file mode 100644
index 0000000..bae8a57
--- /dev/null
+++ b/src/op/call/call_indirect.c
@@ -0,0 +1,49 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <stdio.h>
+
+static int op(struct nw_interp *const i, FILE *const f)
+{
+    varuint32 type_index;
+    varuint1 reserved;
+
+    if (varuint32_read(f, &type_index))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return 1;
+    }
+    else if (varuint1_read(f, &reserved))
+    {
+        LOG("%s: varuint1_read failed\n", __func__);
+        return 1;
+    }
+    else if (reserved)
+    {
+        LOG("%s: unexpected non-zero reserved value %u\n",
+            __func__, (unsigned)reserved);
+        return 1;
+    }
+
+    return 0;
+}
+
+int op_call_indirect(struct nw_interp *const i)
+{
+    return op(i, i->f);
+}
+
+int check_call_indirect(FILE *const f)
+{
+    return op(NULL, f);
+}
diff --git a/src/op/constants/CMakeLists.txt b/src/op/constants/CMakeLists.txt
new file mode 100644
index 0000000..e5cc8c5
--- /dev/null
+++ b/src/op/constants/CMakeLists.txt
@@ -0,0 +1,13 @@
+# nanowasm, a tiny WebAssembly/Wasm interpreter
+# Copyright (C) 2023-2024  Xavier Del Campo Romero
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+target_sources(${PROJECT_NAME} PRIVATE
+    f32_const.c
+    f64_const.c
+    i32_const.c
+    i64_const.c
+)
diff --git a/src/op/constants/f32_const.c b/src/op/constants/f32_const.c
new file mode 100644
index 0000000..c0c51b9
--- /dev/null
+++ b/src/op/constants/f32_const.c
@@ -0,0 +1,38 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <stddef.h>
+#include <stdio.h>
+
+static int op(struct nw_interp *const i, FILE *const f)
+{
+    varuint32 value;
+
+    if (varuint32_read(f, &value))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+int op_f32_const(struct nw_interp *const i)
+{
+    return op(i, i->f);
+}
+
+int check_f32_const(FILE *const f)
+{
+    return op(NULL, f);
+}
diff --git a/src/op/constants/f64_const.c b/src/op/constants/f64_const.c
new file mode 100644
index 0000000..d88398c
--- /dev/null
+++ b/src/op/constants/f64_const.c
@@ -0,0 +1,38 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <stddef.h>
+#include <stdio.h>
+
+static int op(struct nw_interp *const i, FILE *const f)
+{
+    varuint64 value;
+
+    if (varuint64_read(f, &value))
+    {
+        LOG("%s: varuint64_read failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+int op_f64_const(struct nw_interp *const i)
+{
+    return op(i, i->f);
+}
+
+int check_f64_const(FILE *const f)
+{
+    return op(NULL, f);
+}
diff --git a/src/op/constants/i32_const.c b/src/op/constants/i32_const.c
new file mode 100644
index 0000000..19161d3
--- /dev/null
+++ b/src/op/constants/i32_const.c
@@ -0,0 +1,51 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <nw/interp.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+static int set_value(struct nw_interp *const i, const int32_t src)
+{
+    return interp_stack_push(i, &src, sizeof src);
+}
+
+static int op(struct nw_interp *const i, FILE *const f)
+{
+    varint32 value;
+
+    if (varint32_read(f, &value))
+    {
+        LOG("%s: varint32_read failed\n", __func__);
+        return -1;
+    }
+    else if (i && set_value(i, value))
+    {
+        LOG("%s: set_value failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+int op_i32_const(struct nw_interp *const i)
+{
+    return op(i, i->f);
+}
+
+int check_i32_const(FILE *const f)
+{
+    return op(NULL, f);
+}
diff --git a/src/op/constants/i64_const.c b/src/op/constants/i64_const.c
new file mode 100644
index 0000000..53f4237
--- /dev/null
+++ b/src/op/constants/i64_const.c
@@ -0,0 +1,38 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <stddef.h>
+#include <stdio.h>
+
+static int op(struct nw_interp *const i, FILE *const f)
+{
+    varint64 value;
+
+    if (varint64_read(f, &value))
+    {
+        LOG("%s: varint32_read failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+int op_i64_const(struct nw_interp *const i)
+{
+    return op(i, i->f);
+}
+
+int check_i64_const(FILE *const f)
+{
+    return op(NULL, f);
+}
diff --git a/src/op/control_flow/CMakeLists.txt b/src/op/control_flow/CMakeLists.txt
new file mode 100644
index 0000000..832f09e
--- /dev/null
+++ b/src/op/control_flow/CMakeLists.txt
@@ -0,0 +1,20 @@
+# nanowasm, a tiny WebAssembly/Wasm interpreter
+# Copyright (C) 2023-2024  Xavier Del Campo Romero
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+target_sources(${PROJECT_NAME} PRIVATE
+    block.c
+    br.c
+    br_if.c
+    br_table.c
+    else.c
+    end.c
+    if.c
+    loop.c
+    nop.c
+    return.c
+    unreachable.c
+)
diff --git a/src/op/control_flow/block.c b/src/op/control_flow/block.c
new file mode 100644
index 0000000..56f72f1
--- /dev/null
+++ b/src/op/control_flow/block.c
@@ -0,0 +1,75 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/interp.h>
+#include <nw/types.h>
+#include <errno.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+
+static int push(struct nw_interp *const i, FILE *const f)
+{
+    const long pc = ftell(f);
+
+    if (pc < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        i->exception = "I/O error";
+        return -1;
+    }
+
+    struct nw_frame *const fp = i->fp;
+    struct nw_block *const p = interp_stackptr(i);
+    const struct nw_block b =
+    {
+        .pc = pc,
+        .prev = fp->last_block
+    };
+
+    if (interp_stack_push(i, &b, sizeof b))
+    {
+        LOG("%s: interp_stack_push failed\n", __func__);
+        return -1;
+    }
+
+    fp->last_block = p;
+    return 0;
+}
+
+static int op(struct nw_interp *const i, FILE *const f)
+{
+    varint7 sig;
+
+    if (varint7_read(f, &sig))
+    {
+        LOG("%s: varint7_read failed\n", __func__);
+        return -1;
+    }
+    else if (i && push(i, f))
+    {
+        LOG("%s: push failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+int op_block(struct nw_interp *const i)
+{
+    return op(i, i->f);
+}
+
+int check_block(FILE *const f)
+{
+    return op(NULL, f);
+}
diff --git a/src/op/control_flow/br.c b/src/op/control_flow/br.c
new file mode 100644
index 0000000..df3aacb
--- /dev/null
+++ b/src/op/control_flow/br.c
@@ -0,0 +1,38 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <stddef.h>
+#include <stdio.h>
+
+static int op(struct nw_interp *const i, FILE *const f)
+{
+    varuint32 relative_depth;
+
+    if (varuint32_read(f, &relative_depth))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+int op_br(struct nw_interp *const i)
+{
+    return op(i, i->f);
+}
+
+int check_br(FILE *const f)
+{
+    return op(NULL, f);
+}
diff --git a/src/op/control_flow/br_if.c b/src/op/control_flow/br_if.c
new file mode 100644
index 0000000..25bfdee
--- /dev/null
+++ b/src/op/control_flow/br_if.c
@@ -0,0 +1,95 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/interp.h>
+#include <nw/types.h>
+#include <errno.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+
+static int branch(struct nw_interp *const i, const varuint32 relative_depth)
+{
+    const struct nw_block *b = i->fp->last_block;
+    static const char exc[] = "relative depth and block count mismatch";
+
+    for (varuint32 d = 0; b && d < relative_depth; d++)
+        b = b->prev;
+
+    if (!b)
+    {
+        LOG("%s: %s\n", __func__, exc);
+        i->exception = exc;
+        return -1;
+    }
+
+    if (fseek(i->f, b->pc, SEEK_SET))
+    {
+        LOG("%s: fseek(3): %s\n", __func__, strerror(errno));
+        i->exception = "I/O error";
+        return -1;
+    }
+
+    return 0;
+}
+
+static bool cond(struct nw_interp *const i)
+{
+    int32_t value;
+
+    if (interp_stack_pop(i, &value, sizeof value))
+    {
+        LOG("%s: interp_stack_pop failed\n", __func__);
+        return -1;
+    }
+
+    return value;
+}
+
+static int br_if(struct nw_interp *const i, const varuint32 relative_depth)
+{
+    if (cond(i) && branch(i, relative_depth))
+    {
+        LOG("%s: branch failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+static int op(struct nw_interp *const i, FILE *const f)
+{
+    varuint32 relative_depth;
+
+    if (varuint32_read(f, &relative_depth))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return 1;
+    }
+    else if (i && br_if(i, relative_depth))
+    {
+        LOG("%s: br_if failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+int op_br_if(struct nw_interp *const i)
+{
+    return op(i, i->f);
+}
+
+int check_br_if(FILE *const f)
+{
+    return op(NULL, f);
+}
diff --git a/src/op/control_flow/br_table.c b/src/op/control_flow/br_table.c
new file mode 100644
index 0000000..837cdcd
--- /dev/null
+++ b/src/op/control_flow/br_table.c
@@ -0,0 +1,56 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <stddef.h>
+#include <stdio.h>
+
+static int op(struct nw_interp *const i, FILE *const f)
+{
+    varuint32 target_count, default_target;
+
+    if (varuint32_read(f, &target_count))
+    {
+        LOG("%s: varuint32_read target_count failed\n", __func__);
+        return -1;
+    }
+
+    for (varuint32 i = 0; i < target_count; i++)
+    {
+        varuint32 target_table;
+
+        if (varuint32_read(f, &target_table))
+        {
+            LOG("%s: varuint32_read target_table failed\n",
+                __func__);
+            return -1;
+        }
+    }
+
+    if (varuint32_read(f, &default_target))
+    {
+        LOG("%s: varuint32_read default_target failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+int op_br_table(struct nw_interp *const i)
+{
+    return op(i, i->f);
+}
+
+int check_br_table(FILE *const f)
+{
+    return op(NULL, f);
+}
diff --git a/src/op/control_flow/else.c b/src/op/control_flow/else.c
new file mode 100644
index 0000000..fb839f0
--- /dev/null
+++ b/src/op/control_flow/else.c
@@ -0,0 +1,21 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+
+int op_else(struct nw_interp *const i)
+{
+    return -1;
+}
+
+int check_else(FILE *const f)
+{
+    return 0;
+}
diff --git a/src/op/control_flow/end.c b/src/op/control_flow/end.c
new file mode 100644
index 0000000..5f193d9
--- /dev/null
+++ b/src/op/control_flow/end.c
@@ -0,0 +1,24 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <stdbool.h>
+
+int op_end(struct nw_interp *const i)
+{
+    /* TODO: this is not correct. end can appear anywhere in a function. */
+    i->exit = true;
+    return 0;
+}
+
+int check_end(FILE *const f)
+{
+    return 0;
+}
diff --git a/src/op/control_flow/if.c b/src/op/control_flow/if.c
new file mode 100644
index 0000000..1d5e838
--- /dev/null
+++ b/src/op/control_flow/if.c
@@ -0,0 +1,36 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+
+static int op(struct nw_interp *const i, FILE *const f)
+{
+    varint7 sig;
+
+    if (varint7_read(f, &sig))
+    {
+        LOG("%s: varint7_read failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+int op_if(struct nw_interp *const i)
+{
+    return op(i, i->f);
+}
+
+int check_if(FILE *const f)
+{
+    return op(NULL, f);
+}
diff --git a/src/op/control_flow/loop.c b/src/op/control_flow/loop.c
new file mode 100644
index 0000000..5020f23
--- /dev/null
+++ b/src/op/control_flow/loop.c
@@ -0,0 +1,36 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+
+static int op(struct nw_interp *const i, FILE *const f)
+{
+    varint7 sig;
+
+    if (varint7_read(f, &sig))
+    {
+        LOG("%s: varint7_read failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+int op_loop(struct nw_interp *const i)
+{
+    return op(i, i->f);
+}
+
+int check_loop(FILE *const f)
+{
+    return op(NULL, f);
+}
diff --git a/src/op/control_flow/nop.c b/src/op/control_flow/nop.c
new file mode 100644
index 0000000..356b7b0
--- /dev/null
+++ b/src/op/control_flow/nop.c
@@ -0,0 +1,22 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/interp.h>
+
+int op_nop(struct nw_interp *const i)
+{
+    return 0;
+}
+
+int check_nop(FILE *const f)
+{
+    return 0;
+}
diff --git a/src/op/control_flow/return.c b/src/op/control_flow/return.c
new file mode 100644
index 0000000..abddea7
--- /dev/null
+++ b/src/op/control_flow/return.c
@@ -0,0 +1,30 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/interp.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <stdio.h>
+
+int op_return(struct nw_interp *const i)
+{
+    if (interp_pop(i))
+    {
+        LOG("%s: interp_pop failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+int check_return(FILE *const f)
+{
+    return 0;
+}
diff --git a/src/op/control_flow/unreachable.c b/src/op/control_flow/unreachable.c
new file mode 100644
index 0000000..8f1982c
--- /dev/null
+++ b/src/op/control_flow/unreachable.c
@@ -0,0 +1,25 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <stdbool.h>
+#include <stdio.h>
+
+int op_unreachable(struct nw_interp *const i)
+{
+    i->exception = "Unreachable instruction";
+    i->exit = true;
+    return 1;
+}
+
+int check_unreachable(FILE *const f)
+{
+    return 0;
+}
diff --git a/src/op/memory/CMakeLists.txt b/src/op/memory/CMakeLists.txt
new file mode 100644
index 0000000..ca4ba5a
--- /dev/null
+++ b/src/op/memory/CMakeLists.txt
@@ -0,0 +1,12 @@
+# nanowasm, a tiny WebAssembly/Wasm interpreter
+# Copyright (C) 2023-2024  Xavier Del Campo Romero
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+target_sources(${PROJECT_NAME} PRIVATE
+    current_memory.c
+    i32_load.c
+    i32_store.c
+)
diff --git a/src/op/memory/current_memory.c b/src/op/memory/current_memory.c
new file mode 100644
index 0000000..c67d425
--- /dev/null
+++ b/src/op/memory/current_memory.c
@@ -0,0 +1,44 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <stddef.h>
+#include <stdio.h>
+
+static int op(struct nw_interp *const i, FILE *const f)
+{
+    varuint1 reserved;
+
+    if (varuint1_read(f, &reserved))
+    {
+        LOG("%s: varuint1_read failed\n", __func__);
+        return 1;
+    }
+    else if (reserved)
+    {
+        LOG("%s: unexpected non-zero reserved value %u\n",
+            __func__, (unsigned)reserved);
+        return 1;
+    }
+
+    return 0;
+}
+
+int op_current_memory(struct nw_interp *const i)
+{
+    return op(i, i->f);
+}
+
+int check_current_memory(FILE *const f)
+{
+    return op(NULL, f);
+}
diff --git a/src/op/memory/i32_load.c b/src/op/memory/i32_load.c
new file mode 100644
index 0000000..04dbec7
--- /dev/null
+++ b/src/op/memory/i32_load.c
@@ -0,0 +1,76 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/interp.h>
+#include <nw/types.h>
+#include <stddef.h>
+#include <stdio.h>
+
+static int load(struct nw_interp *const i, const varuint32 flags,
+    const varuint32 offset)
+{
+    enum {ALIGN = 2};
+    int32_t value;
+
+    if (flags != ALIGN)
+    {
+        LOG("%s: expected 32-bit alignment (%d), got %lu\n",
+            __func__, ALIGN, (unsigned long)flags);
+        i->exception = "unaligned access";
+        return -1;
+    }
+    else if (interp_heap_load(i, offset, &value, sizeof value))
+    {
+        LOG("%s: interp_heap_load failed\n", __func__);
+        return -1;
+    }
+    else if (interp_stack_push(i, &value, sizeof value))
+    {
+        LOG("%s: interp_stack_push failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+static int op(struct nw_interp *const i, FILE *const f)
+{
+    varint32 flags, offset;
+
+    if (varint32_read(f, &flags))
+    {
+        LOG("%s: varint32_read flags failed\n", __func__);
+        return 1;
+    }
+    else if (varint32_read(f, &offset))
+    {
+        LOG("%s: varint32_read offset failed\n", __func__);
+        return 1;
+    }
+    else if (i && load(i, flags, offset))
+    {
+        LOG("%s: load failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+int op_i32_load(struct nw_interp *const i)
+{
+    return op(i, i->f);
+}
+
+int check_i32_load(FILE *const f)
+{
+    return op(NULL, f);
+}
diff --git a/src/op/memory/i32_store.c b/src/op/memory/i32_store.c
new file mode 100644
index 0000000..212cd86
--- /dev/null
+++ b/src/op/memory/i32_store.c
@@ -0,0 +1,125 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <nw/interp.h>
+#include <stdint.h>
+#include <stddef.h>
+#include <stdio.h>
+
+static int store(struct nw_interp *const i, const varuint32 flags,
+    const varuint32 offset)
+{
+    enum {ALIGN = 2};
+
+    if (flags != ALIGN)
+    {
+        LOG("%s: expected 32-bit alignment (%d), got %lu\n",
+            __func__, ALIGN, (unsigned long)flags);
+        i->exception = "unaligned access";
+        return -1;
+    }
+
+    int32_t value, addr;
+
+    if (interp_stack_pop(i, &value, sizeof value))
+    {
+        LOG("%s: inter_stack_pop value failed\n", __func__);
+        return -1;
+    }
+    else if (interp_stack_pop(i, &addr, sizeof addr))
+    {
+        LOG("%s: inter_stack_pop addr failed\n", __func__);
+        return -1;
+    }
+    else if (offset > SIZE_MAX - addr)
+    {
+        static const char exc[] = "offset address overflow";
+
+        LOG("%s: %s\n", __func__, exc);
+        i->exception = exc;
+        return -1;
+    }
+    else if (interp_heap_store(i, offset + addr, &value, sizeof value))
+    {
+        LOG("%s: interp_heap_store failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+#if 0
+    stack_i -= sizeof addr;
+
+    if (max < addr || offset >= max - addr)
+    {
+        LOG("%s: heap overflow\n", __func__);
+        i->exception = "heap overflow";
+        return -1;
+    }
+
+    const size_t raddr = offset + addr;
+
+    if (raddr % sizeof addr)
+    {
+        LOG("%s: unaligned memory address\n", __func__);
+        i->exception = "unaligned access";
+        return -1;
+    }
+    else if (stack_i < sizeof (uint32_t))
+    {
+        LOG("%s: stack underflow (value)\n", __func__);
+        i->exception = "stack underflow";
+        return -1;
+    }
+
+    const int32_t value = htoni32(*stackptr);
+    void *dst = &((char *)i->cfg.heap.buf)[raddr];
+
+    *(int32_t *)dst = value;
+    stack_i -= sizeof addr;
+    i->stack_i = stack_i;
+    return 0;
+#endif
+}
+
+static int op(struct nw_interp *const i, FILE *const f)
+{
+    varuint32 flags, offset;
+
+    if (varuint32_read(f, &flags))
+    {
+        LOG("%s: varint32_read flags failed\n", __func__);
+        return -1;
+    }
+    else if (varuint32_read(f, &offset))
+    {
+        LOG("%s: varint32_read offset failed\n", __func__);
+        return -1;
+    }
+    else if (i && store(i, flags, offset))
+    {
+        LOG("%s: store failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+int op_i32_store(struct nw_interp *const i)
+{
+    return op(i, i->f);
+}
+
+int check_i32_store(FILE *const f)
+{
+    return op(NULL, f);
+}
diff --git a/src/op/numeric/CMakeLists.txt b/src/op/numeric/CMakeLists.txt
new file mode 100644
index 0000000..a259506
--- /dev/null
+++ b/src/op/numeric/CMakeLists.txt
@@ -0,0 +1,10 @@
+# nanowasm, a tiny WebAssembly/Wasm interpreter
+# Copyright (C) 2023-2024  Xavier Del Campo Romero
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+target_sources(${PROJECT_NAME} PRIVATE
+    i32_sub.c
+)
diff --git a/src/op/numeric/i32_sub.c b/src/op/numeric/i32_sub.c
new file mode 100644
index 0000000..c3d1352
--- /dev/null
+++ b/src/op/numeric/i32_sub.c
@@ -0,0 +1,66 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/interp.h>
+#include <nw/types.h>
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+/* Inspired by "INT32-C. Ensure that operations on signed integers do
+ * not result in overflow". */
+static bool signed_overflow(const int32_t a, const int32_t b)
+{
+    return (b > 0 && a < INT32_MIN + b)
+        || (b < 0 && a > INT32_MAX + b);
+}
+
+int op_i32_sub(struct nw_interp *const i)
+{
+    int32_t op1, op2;
+
+    if (interp_stack_pop(i, &op2, sizeof op2))
+    {
+        LOG("%s: interp_stack_pop %s failed\n", __func__, "op2");
+        return -1;
+    }
+    else if (interp_stack_pop(i, &op1, sizeof op1))
+    {
+        LOG("%s: interp_stack_pop %s failed\n", __func__, "op1");
+        return -1;
+    }
+    else if (signed_overflow(op2, op1))
+    {
+        LOG("%s: signed integer overflow (op1=%" PRIi32 ", op2=%" PRIi32 ")\n",
+            __func__, op1, op2);
+        i->exception = "signed integer overflow";
+        return 1;
+    }
+
+    const int32_t result = op2 - op1;
+
+    if (interp_stack_push(i, &result, sizeof result))
+    {
+        LOG("%s: interp_stack_push failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+int check_i32_sub(FILE *const f)
+{
+    return 0;
+}
diff --git a/src/op/variable_access/CMakeLists.txt b/src/op/variable_access/CMakeLists.txt
new file mode 100644
index 0000000..314b5bf
--- /dev/null
+++ b/src/op/variable_access/CMakeLists.txt
@@ -0,0 +1,14 @@
+# nanowasm, a tiny WebAssembly/Wasm interpreter
+# Copyright (C) 2023-2024  Xavier Del Campo Romero
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+target_sources(${PROJECT_NAME} PRIVATE
+    get_global.c
+    get_local.c
+    set_global.c
+    set_local.c
+    tee_local.c
+)
diff --git a/src/op/variable_access/get_global.c b/src/op/variable_access/get_global.c
new file mode 100644
index 0000000..d38f2d0
--- /dev/null
+++ b/src/op/variable_access/get_global.c
@@ -0,0 +1,100 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/interp.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+static int get_i32(struct nw_interp *const i, const void *const src)
+{
+    return interp_stack_push(i, src, sizeof (int32_t));
+}
+
+static int get_i64(struct nw_interp *const i, const void *const src)
+{
+    return interp_stack_push(i, src, sizeof (int64_t));
+}
+
+static int get_f32(struct nw_interp *const i, const void *const src)
+{
+    return interp_stack_push(i, src, sizeof (float));
+}
+
+static int get_f64(struct nw_interp *const i, const void *const src)
+{
+    return interp_stack_push(i, src, sizeof (double));
+}
+
+static int get_global(struct nw_interp *const i, const varuint32 global_index)
+{
+    struct nw_gframe *gfr;
+    varuint32 idx;
+
+    for (idx = global_index, gfr = i->gfp; gfr; gfr = gfr->next)
+        if (idx == global_index)
+            break;
+
+    if (!gfr)
+    {
+        LOG("%s: cannot access global variable %lu\n", __func__,
+            (unsigned long)global_index);
+        i->exception = "global variable index out of bounds";
+        return -1;
+    }
+
+    static int (*const get[])(struct nw_interp *, const void *) =
+    {
+        [VALUE_TYPE_I32] = get_i32,
+        [VALUE_TYPE_I64] = get_i64,
+        [VALUE_TYPE_F32] = get_f32,
+        [VALUE_TYPE_F64] = get_f64,
+    };
+
+    if (get[gfr->type](i, gfr + 1))
+    {
+        LOG("%s: get type %s failed\n", __func__, value_type_tostr(gfr->type));
+        return -1;
+    }
+
+    return 0;
+}
+
+static int op(struct nw_interp *const i, FILE *const f)
+{
+    varuint32 global_index;
+
+    if (varuint32_read(f, &global_index))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return 1;
+    }
+    else if (i && get_global(i, global_index))
+    {
+        LOG("%s: get_global failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+int op_get_global(struct nw_interp *const i)
+{
+    return op(i, i->f);
+}
+
+int check_get_global(FILE *const f)
+{
+    return op(NULL, f);
+}
diff --git a/src/op/variable_access/get_local.c b/src/op/variable_access/get_local.c
new file mode 100644
index 0000000..745a2e7
--- /dev/null
+++ b/src/op/variable_access/get_local.c
@@ -0,0 +1,112 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <nw/interp.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+static int get_i32(struct nw_interp *const i, const void *const data,
+    const varuint32 idx)
+{
+    const int32_t *const src = (const int32_t *)data + idx;
+
+    return interp_stack_push(i, src, sizeof (*src));
+}
+
+static int get_i64(struct nw_interp *const i, const void *const data,
+    const varuint32 idx)
+{
+    const int64_t *const src = (const int64_t *)data + idx;
+
+    return interp_stack_push(i, src, sizeof (*src));
+}
+
+static int get_f32(struct nw_interp *const i, const void *const data,
+    const varuint32 idx)
+{
+    const float *const src = (const float *)data + idx;
+
+    return interp_stack_push(i, src, sizeof (*src));
+}
+
+static int get_f64(struct nw_interp *const i, const void *const data,
+    const varuint32 idx)
+{
+    const double *const src = (const double *)data + idx;
+
+    return interp_stack_push(i, src, sizeof (*src));
+}
+
+static int get_local(const varuint32 local_index, struct nw_interp *const i)
+{
+    struct nw_frame *fr;
+    varuint32 idx;
+
+    for (idx = local_index, fr = i->fp; fr; fr = fr->next)
+        if (idx < fr->n_locals)
+            break;
+
+    if (!fr)
+    {
+        LOG("%s: cannot access local variable %lu\n", __func__,
+            (unsigned long)local_index);
+        i->exception = "local variable index out of bounds";
+        return -1;
+    }
+
+    static int (*const get[])(struct nw_interp *, const void *, varuint32) =
+    {
+        [VALUE_TYPE_I32] = get_i32,
+        [VALUE_TYPE_I64] = get_i64,
+        [VALUE_TYPE_F32] = get_f32,
+        [VALUE_TYPE_F64] = get_f64,
+    };
+
+    if (get[fr->local_type](i, fr + 1, idx))
+    {
+        LOG("%s: get type %d failed\n", __func__, fr->local_type);
+        return -1;
+    }
+
+    return 0;
+}
+
+static int op(struct nw_interp *const i, FILE *const f)
+{
+    varuint32 local_index;
+
+    if (varuint32_read(f, &local_index))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return 1;
+    }
+    else if (i && get_local(local_index, i))
+    {
+        LOG("%s: get_local failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+int op_get_local(struct nw_interp *const i)
+{
+    return op(i, i->f);
+}
+
+int check_get_local(FILE *const f)
+{
+    return op(NULL, f);
+}
diff --git a/src/op/variable_access/set_global.c b/src/op/variable_access/set_global.c
new file mode 100644
index 0000000..d1229c5
--- /dev/null
+++ b/src/op/variable_access/set_global.c
@@ -0,0 +1,38 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <stddef.h>
+#include <stdio.h>
+
+static int op(struct nw_interp *const i, FILE *const f)
+{
+    varuint32 global_index;
+
+    if (varuint32_read(f, &global_index))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return 1;
+    }
+
+    return 0;
+}
+
+int op_set_global(struct nw_interp *const i)
+{
+    return op(i, i->f);
+}
+
+int check_set_global(FILE *const f)
+{
+    return op(NULL, f);
+}
diff --git a/src/op/variable_access/set_local.c b/src/op/variable_access/set_local.c
new file mode 100644
index 0000000..8cf6440
--- /dev/null
+++ b/src/op/variable_access/set_local.c
@@ -0,0 +1,124 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+
+static int set_i32(struct nw_interp *const i, void *const data,
+    const varuint32 idx)
+{
+    const void *const stackptr = (const char *)i->cfg.stack.buf + i->stack_i;
+    const int32_t *const src = (const int32_t *)stackptr - 1;
+    int32_t *const dst = (int32_t *)data + idx;
+
+    *dst = *src;
+    return 0;
+}
+
+static int set_i64(struct nw_interp *const i, void *const data,
+    const varuint32 idx)
+{
+    const void *const stackptr = (const char *)i->cfg.stack.buf + i->stack_i;
+    const int64_t *const src = (const int64_t *)stackptr - 1;
+    int64_t *const dst = (int64_t *)data + idx;
+
+    *dst = *src;
+    return 0;
+}
+
+static int set_f32(struct nw_interp *const i, void *const data,
+    const varuint32 idx)
+{
+    const void *const stackptr = (const char *)i->cfg.stack.buf + i->stack_i;
+    const float *const src = (const float *)stackptr - 1;
+    float *const dst = (float *)data + idx;
+
+    *dst = *src;
+    return 0;
+}
+
+static int set_f64(struct nw_interp *const i, void *const data,
+    const varuint32 idx)
+{
+    const void *const stackptr = (const char *)i->cfg.stack.buf + i->stack_i;
+    const double *const src = (const double *)stackptr - 1;
+    double *const dst = (double *)data + idx;
+
+    *dst = *src;
+    return 0;
+}
+
+static int set_local(const varuint32 local_index, struct nw_interp *const i)
+{
+    struct nw_frame *fr;
+    varuint32 idx;
+
+    for (idx = local_index, fr = i->fp; fr; fr = fr->next)
+        if (idx < fr->n_locals)
+            break;
+
+    if (!fr)
+    {
+        LOG("%s: cannot access local variable %lu\n", __func__,
+            (unsigned long)local_index);
+        i->exception = "local variable index out of bounds";
+        return -1;
+    }
+
+    static int (*const set[])(struct nw_interp *, void *, varuint32) =
+    {
+        [VALUE_TYPE_I32] = set_i32,
+        [VALUE_TYPE_I64] = set_i64,
+        [VALUE_TYPE_F32] = set_f32,
+        [VALUE_TYPE_F64] = set_f64,
+    };
+
+    if (set[fr->local_type](i, fr + 1, idx))
+    {
+        LOG("%s: set type %d failed\n", __func__, fr->local_type);
+        return -1;
+    }
+
+    return 0;
+}
+
+static int op(struct nw_interp *const i, FILE *const f)
+{
+    varuint32 local_index;
+
+    if (varuint32_read(f, &local_index))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return 1;
+    }
+    else if (i && set_local(local_index, i))
+    {
+        LOG("%s: set_local failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+int op_set_local(struct nw_interp *const i)
+{
+    return op(i, i->f);
+}
+
+int check_set_local(FILE *const f)
+{
+    return op(NULL, f);
+}
diff --git a/src/op/variable_access/tee_local.c b/src/op/variable_access/tee_local.c
new file mode 100644
index 0000000..00d7832
--- /dev/null
+++ b/src/op/variable_access/tee_local.c
@@ -0,0 +1,38 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/ops.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <stddef.h>
+#include <stdio.h>
+
+static int op(struct nw_interp *const i, FILE *const f)
+{
+    varuint32 local_index;
+
+    if (varuint32_read(f, &local_index))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return 1;
+    }
+
+    return 0;
+}
+
+int op_tee_local(struct nw_interp *const i)
+{
+    return op(i, i->f);
+}
+
+int check_tee_local(FILE *const f)
+{
+    return op(NULL, f);
+}
diff --git a/src/run.c b/src/run.c
new file mode 100644
index 0000000..e1cca7d
--- /dev/null
+++ b/src/run.c
@@ -0,0 +1,42 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nanowasm/nw.h>
+#include <nw/interp.h>
+#include <nw/log.h>
+#include <nw/search.h>
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+
+enum nw_state nw_run(struct nw_inst *const i)
+{
+    struct nw_interp *const in = &i->interp;
+    union nw_inst_state *const s = &i->state;
+
+    if (interp_run(in))
+    {
+        LOG("%s: interp_run failed\n", __func__);
+
+        if (in->exception)
+        {
+            s->exception = in->exception;
+            return NW_STATE_EXCEPTION;
+        }
+
+        return NW_STATE_FATAL;
+    }
+    else if (in->exit)
+    {
+        s->retval = in->retval;
+        return NW_STATE_RETURNED;
+    }
+
+    return NW_STATE_AGAIN;
+}
diff --git a/src/search.c b/src/search.c
new file mode 100644
index 0000000..622b74c
--- /dev/null
+++ b/src/search.c
@@ -0,0 +1,181 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/search.h>
+#include <nw/log.h>
+#include <nw/fstring.h>
+#include <nw/sections.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <errno.h>
+#include <stdint.h>
+#include <string.h>
+
+static int ensure_export(const char *const fn,
+    const struct nw_mod *const m, FILE *const f, varuint32 *const out)
+{
+    if (!m->sections.export)
+    {
+        LOG("%s: export section not found", __func__);
+        return -1;
+    }
+    else if (fseek(f, m->sections.export, SEEK_SET))
+    {
+        LOG("%s: fseek(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    varuint32 count;
+
+    if (varuint32_read(f, &count))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+
+    for (varuint32 i = 0; i < count; i++)
+    {
+        varuint32 len;
+        bool found = false;
+
+        if (varuint32_read(f, &len))
+        {
+            LOG("%s: varuint32_read failed\n", __func__);
+            return -1;
+        }
+        else if (len != strlen(fn))
+        {
+            if (fseek(f, len, SEEK_CUR))
+            {
+                LOG("%s: fseek(3): %s\n", __func__, strerror(errno));
+                return -1;
+            }
+        }
+        else if (!fstrcmp(fn, f, false))
+            found = true;
+
+        uint8_t kind;
+
+        if (!fread(&kind, sizeof kind, 1, f))
+        {
+            LOG("%s: fread(3) failed: feof=%d, ferror=%d\n", __func__,
+                feof(f), ferror(f));
+            return -1;
+        }
+
+        varuint32 index;
+
+        if (varuint32_read(f, &index))
+        {
+            LOG("%s: varuint32_read failed\n", __func__);
+            return -1;
+        }
+        else if (found)
+        {
+            if (kind != NW_KIND_FUNCTION)
+            {
+                LOG("%s: expected kind %d, got %d\n", __func__,
+                    NW_KIND_FUNCTION, kind);
+                return -1;
+            }
+
+            *out = index;
+            return 0;
+        }
+    }
+
+    return -1;
+}
+
+static int get_function_index(const struct nw_mod *const m,
+    const varuint32 index, varuint32 *const findex)
+{
+    const size_t n = m->cfg.n_imports;
+
+    if (index < n)
+    {
+        LOG("%s: index (%lu) must be greater than number of imports (%zu)\n",
+            __func__, (unsigned long)index, n);
+        return -1;
+    }
+
+    *findex = index - n;
+    return 0;
+}
+
+static int get_fn_start(const struct nw_mod *const m, FILE *const f,
+    const varuint32 index, struct search_fn *const out)
+{
+    const struct section s =
+    {
+        .cfg = &m->cfg,
+        .f = f
+    };
+
+    struct section_function sf;
+    struct section_code c;
+
+    if (section_function(&s, m, index, &sf))
+    {
+        LOG("%s: section_function failed\n", __func__);
+        return -1;
+    }
+    else if (section_code(&s, m, index, &c))
+    {
+        LOG("%s: section_code failed\n", __func__);
+        return -1;
+    }
+
+    out->start = c.start;
+    out->index = index;
+    return 0;
+}
+
+int search_exported_fn(const char *const fn, const struct nw_mod *const m,
+    FILE *const f, struct search_fn *const out)
+{
+    varuint32 index, findex;
+
+    if (ensure_export(fn, m, f, &index))
+    {
+        LOG("%s: %s not an exported function\n", __func__, fn);
+        return -1;
+    }
+    else if (get_function_index(m, index, &findex))
+    {
+        LOG("%s: get_function_index failed\n", __func__);
+        return -1;
+    }
+    else if (get_fn_start(m, f, findex, out))
+    {
+        LOG("%s: get_fn_start %s failed\n", __func__, fn);
+        return -1;
+    }
+
+    return 0;
+}
+
+int search_fn(const varuint32 index, const struct nw_mod *const m,
+    FILE *const f, struct search_fn *const out)
+{
+    varuint32 findex;
+
+    if (get_function_index(m, index, &findex))
+    {
+        LOG("%s: get_function_index failed\n", __func__);
+        return -1;
+    }
+    else if (get_fn_start(m, f, findex, out))
+    {
+        LOG("%s: get_fn_start failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
diff --git a/src/section/CMakeLists.txt b/src/section/CMakeLists.txt
new file mode 100644
index 0000000..772dd3f
--- /dev/null
+++ b/src/section/CMakeLists.txt
@@ -0,0 +1,22 @@
+# nanowasm, a tiny WebAssembly/Wasm interpreter
+# Copyright (C) 2023-2024  Xavier Del Campo Romero
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+target_sources(${PROJECT_NAME} PRIVATE
+    code.c
+    common.c
+    custom.c
+    data.c
+    element.c
+    export.c
+    function.c
+    global.c
+    import.c
+    memory.c
+    start.c
+    table.c
+    type.c
+)
diff --git a/src/section/code.c b/src/section/code.c
new file mode 100644
index 0000000..da45047
--- /dev/null
+++ b/src/section/code.c
@@ -0,0 +1,429 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nanowasm/nw.h>
+#include <nw/opcodes.h>
+#include <nw/interp.h>
+#include <nw/sections.h>
+#include <nw/types.h>
+#include <errno.h>
+#include <inttypes.h>
+#include <limits.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+
+static int check_body(FILE *const f, const unsigned long n)
+{
+    unsigned long rem = n;
+
+    while (rem)
+    {
+        const long before = ftell(f);
+        uint8_t byte;
+
+        if (before < 0)
+        {
+            LOG("%s: ftell(3) before: %s\n", __func__, strerror(errno));
+            return -1;
+        }
+        else if (!fread(&byte, sizeof byte, 1, f))
+        {
+            LOG("%s: fread(3) failed, feof=%d, ferror=%d\n",
+                __func__, feof(f), ferror(f));
+            return -1;
+        }
+        else if (rem == 1 && byte != OP_END)
+        {
+            LOG("%s: unexpected opcode %#" PRIx8 " at body end\n",
+                __func__, byte);
+            return -1;
+        }
+        else if (interp_check_opcode(byte, f))
+        {
+            LOG("%s: interp_check_opcode failed\n", __func__);
+            return -1;
+        }
+
+        const long after = ftell(f);
+
+        if (after < 0)
+        {
+            LOG("%s: ftell(3) after: %s\n", __func__, strerror(errno));
+            return -1;
+        }
+
+        rem -= after - before;
+    }
+
+    return 0;
+}
+
+#if 0
+
+static int push_locals(struct nw_interp *const i,
+    const struct nw_frame *const f)
+{
+    const enum value_type t = f->local_type;
+    const size_t typesz = get_type_size(t);
+    const unsigned long n = f->n_locals;
+
+    if (mul_overflow(typesz, f->n_locals))
+    {
+        LOG("%s: local variables size mul overflow", __func__);
+        i->exception = "mul overfllow";
+        return -1;
+    }
+
+    const size_t totalsz = typesz * n, max = i->cfg.stack.n;
+
+    if (totalsz > max || i->stack_i > max - totalsz)
+    {
+        LOG("%s: cannot allocate locals\n", __func__);
+        i->exception = "stack overflow";
+        return 1;
+    }
+
+    init_locals(t, n, interp_stackptr(i));
+    i->stack_i += totalsz;
+    return 0;
+}
+
+static int push_block(struct nw_interp *const i)
+{
+    const long pc = ftell(i->f);
+
+    if (pc < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    const struct nw_block b =
+    {
+        .pc = pc
+    };
+
+    if (interp_stack_push(i, &b, sizeof b))
+    {
+        LOG("%s: interp_stack_push failed\n", __func__);
+        return -1;
+    }
+
+    struct nw_block *const p = (struct nw_block *)interp_stackptr(i) - 1;
+
+    if (i->fp->block)
+    {
+        for (struct nw_block *b = i->fp->block; b; b = b->next)
+            if (!b->next)
+            {
+                b->next = p;
+                break;
+            }
+    }
+    else
+        i->fp->block = p;
+
+    return 0;
+}
+
+static int loop_push_blocks(struct nw_interp *const i)
+{
+    for (;;)
+    {
+        uint8_t op;
+
+        if (!fread(&op, sizeof op, 1, i->f))
+        {
+            LOG("%s: fread(3) failed, feof=%d, ferror=%d\n", __func__,
+                feof(i->f), ferror(i->f));
+            i->exception = "I/O error";
+            return -1;
+        }
+        else if (op >= sizeof ops / sizeof *ops)
+        {
+            LOG("%s: invalid opcode %#" PRIx8 "\n", __func__, op);
+            i->exception = "invalid opcode";
+            return -1;
+        }
+        else if (interp_check_opcode(op, i->f))
+        {
+            LOG("%s: interp_check_opcode failed\n", __func__);
+            return -1;
+        }
+
+        switch (op)
+        {
+            case OP_END:
+                return 0;
+
+            case OP_BLOCK:
+                if (push_block(i))
+                {
+                    LOG("%s: push_block failed\n", __func__);
+                    return -1;
+                }
+
+                break;
+
+            default:
+                break;
+        }
+    }
+}
+
+static int push_blocks(struct nw_interp *const i,
+    const struct nw_frame *const fr)
+{
+    FILE *const f = i->f;
+    const long orig = ftell(f);
+
+    if (orig < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+    else if (loop_push_blocks(i))
+    {
+        LOG("%s: loop_push_blocks failed\n", __func__);
+        return -1;
+    }
+    else if (fseek(f, orig, SEEK_SET))
+    {
+        LOG("%s: fseek(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    return 0;
+}
+#endif
+
+static int push_local_count(struct nw_frame *const f, const varuint32 count,
+    const varint7 type)
+{
+    enum value_type vtype;
+
+    if (get_value_type(type, &vtype))
+    {
+        LOG("%s: get_value_type failed\n", __func__);
+        return -1;
+    }
+
+    f->n_locals = count;
+    f->local_type = vtype;
+    return 0;
+}
+
+static int check_local(FILE *const f, struct nw_frame *const fr)
+{
+    varuint32 count;
+    varint7 type;
+
+    if (varuint32_read(f, &count))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+    else if (varint7_read(f, &type))
+    {
+        LOG("%s: varint7_read failed\n", __func__);
+        return -1;
+    }
+    else if (fr && push_local_count(fr, count, type))
+    {
+        LOG("%s: push_local_count failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+static int check_locals(FILE *const f, struct nw_frame *const fr)
+{
+    varuint32 local_count;
+
+    if (varuint32_read(f, &local_count))
+    {
+        LOG("%s: varuint32_read local_count failed\n", __func__);
+        return -1;
+    }
+
+    for (varuint32 i = 0; i < local_count; i++)
+        if (check_local(f, fr))
+        {
+            LOG("%s: check_local failed\n", __func__);
+            return -1;
+        }
+
+    return 0;
+}
+
+static int check_function_body(FILE *const f, long *const out)
+{
+    varuint32 body_size;
+
+    if (varuint32_read(f, &body_size))
+    {
+        LOG("%s: varuint32_read body_size failed\n", __func__);
+        return -1;
+    }
+
+    const long start = ftell(f);
+
+    if (start < 0)
+    {
+        LOG("%s: ftell(3) start: %s\n", __func__, strerror(errno));
+        return -1;
+    }
+    else if (check_locals(f, NULL))
+    {
+        LOG("%s: check_locals failed\n", __func__);
+        return -1;
+    }
+
+    const long end = ftell(f);
+
+    if (end < 0)
+    {
+        LOG("%s: ftell(3) end: %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    const unsigned long consumed = end - start;
+
+    if (consumed > body_size)
+    {
+        LOG("%s: exceeded function body size\n", __func__);
+        return -1;
+    }
+    else if (check_body(f, body_size - consumed))
+    {
+        LOG("%s: check_body failed\n", __func__);
+        return -1;
+    }
+
+    *out = start;
+    return 0;
+}
+
+static int run(FILE *const f, const varuint32 idx,
+    struct section_code *const out)
+{
+    varuint32 count;
+
+    if (varuint32_read(f, &count))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+    else if (count > ULONG_MAX - 1)
+    {
+        fprintf(stderr, "%s: count overflow\n", __func__);
+        return -1;
+    }
+
+    for (varuint32 i = 0; i < count; i++)
+    {
+        long start;
+
+        if (check_function_body(f, &start))
+        {
+            LOG("%s: check_function_body failed\n", __func__);
+            return -1;
+        }
+        else if (out && i == idx)
+        {
+            out->start = start;
+            return 0;
+        }
+    }
+
+    return 0;
+}
+
+int section_code_check(const struct section *const s, struct nw_mod *const m,
+    const unsigned long len)
+{
+    FILE *const f = s->f;
+
+    if (m->sections.code)
+    {
+        LOG("%s: ignoring duplicate section\n", __func__);
+        return fseek(f, len, SEEK_CUR);
+    }
+
+    const long start = ftell(f);
+
+    if (start < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+    else if (run(f, 0, NULL))
+    {
+        LOG("%s: run failed\n", __func__);
+        return -1;
+    }
+
+    const long end = ftell(f);
+
+    if (end < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    const unsigned long size = end - start;
+
+    if (size != len)
+    {
+        LOG("%s: size exceeded (%lu expected, got %lu)\n",
+                __func__, len, size);
+        return -1;
+    }
+
+    m->sections.code = start;
+    return 0;
+}
+
+int section_code(const struct section *const s, const struct nw_mod *const m,
+    const varuint32 idx, struct section_code *const out)
+{
+    const long offset = m->sections.code;
+
+    if (offset <= 0)
+    {
+        LOG("%s: code section not found", __func__);
+        return -1;
+    }
+    else if (fseek(s->f, offset, SEEK_SET))
+    {
+        LOG("%s: fseek(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    return run(s->f, idx, out);
+}
+
+int section_code_push(FILE *const f, const long pc, struct nw_frame *const fr)
+{
+    if (fseek(f, pc, SEEK_SET))
+    {
+        LOG("%s: fseek(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+    else if (check_locals(f, fr))
+    {
+        LOG("%s: check_local failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
diff --git a/src/section/common.c b/src/section/common.c
new file mode 100644
index 0000000..b768470
--- /dev/null
+++ b/src/section/common.c
@@ -0,0 +1,150 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/sections.h>
+#include <nw/types.h>
+#include <errno.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+
+int check_resizable_limits(FILE *const f, struct resizable_limits *const r)
+{
+    varuint1 flags;
+    varuint32 initial;
+
+    *r = (const struct resizable_limits){0};
+
+    if (varuint1_read(f, &flags))
+    {
+        LOG("%s: varuint1_read failed\n", __func__);
+        return -1;
+    }
+    else if (varuint32_read(f, &initial))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+
+    if (flags)
+    {
+        varuint32 maximum;
+
+        if (varuint32_read(f, &maximum))
+        {
+            LOG("%s: varuint32_read failed\n", __func__);
+            return -1;
+        }
+
+        r->max = maximum;
+        r->max_available = true;
+    }
+
+    static const unsigned long page_size = 64lu * 1024lu;
+
+    if (initial > UINT32_MAX / page_size)
+    {
+        LOG("%s: initial size (%lu) overflow \n", __func__,
+            (unsigned long)initial);
+        return 1;
+    }
+
+    r->sz = initial * page_size;
+    return 0;
+}
+
+size_t get_type_size(const enum value_type type)
+{
+    static const size_t list[] =
+    {
+        [VALUE_TYPE_I32] = sizeof (int32_t),
+        [VALUE_TYPE_I64] = sizeof (int64_t),
+        [VALUE_TYPE_F32] = sizeof (float),
+        [VALUE_TYPE_F64] = sizeof (double)
+    };
+
+    return list[type];
+}
+
+enum
+{
+    I32 = 0x7f,
+    I64 = 0x7e,
+    F32 = 0x7d,
+    F64 = 0x7c,
+    ANYFUNC = 0x70,
+    FUNC = 0x60,
+    BLOCK_TYPE = 0x40
+};
+
+int get_value_type(const varint7 type, enum value_type *const vtype)
+{
+    static const struct size
+    {
+        varint7 type;
+        enum value_type vtype;
+    } sizes[] =
+    {
+        {.type = I32, .vtype = VALUE_TYPE_I32},
+        {.type = I64, .vtype = VALUE_TYPE_I64},
+        {.type = F32, .vtype = VALUE_TYPE_F32},
+        {.type = F64, .vtype = VALUE_TYPE_F64},
+        /* TODO: check this. */
+        {.type = ANYFUNC, .vtype = VALUE_TYPE_I32},
+        /* TODO: check this. */
+        {.type = FUNC, .vtype = VALUE_TYPE_I32},
+        /* TODO: check this. */
+        {.type = BLOCK_TYPE, .vtype = VALUE_TYPE_I32}
+    };
+
+    for (size_t i = 0; i < sizeof sizes / sizeof *sizes; i++)
+    {
+        const struct size *const s = &sizes[i];
+
+        if (type == s->type)
+        {
+            *vtype = s->vtype;
+            return 0;
+        }
+    }
+
+    LOG("%s: unknown type %#hhx\n", __func__, (char)type);
+    return -1;
+}
+
+static int32_t swap_i32(const int32_t in)
+{
+    const int8_t *const p = (const int8_t *)&in;
+
+    return p[0] | (p[1] << 8) | (p[2] << 16) | (p[3] << 24);
+}
+
+int32_t htoni32(const int32_t in)
+{
+    return swap_i32(in);
+}
+
+int32_t ntohi32(const int32_t in)
+{
+    return swap_i32(in);
+}
+
+const char *value_type_tostr(const enum value_type v)
+{
+    static const char *const s[] =
+    {
+#define X(x) [x] = #x,
+        VALUE_TYPES
+#undef X
+    };
+
+    return s[v];
+}
diff --git a/src/section/custom.c b/src/section/custom.c
new file mode 100644
index 0000000..fe06b74
--- /dev/null
+++ b/src/section/custom.c
@@ -0,0 +1,30 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/sections.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+
+int section_custom_check(const struct section *const s, struct nw_mod *const m,
+    const unsigned long len)
+{
+    FILE *const f = s->f;
+
+    if (fseek(f, len, SEEK_CUR))
+    {
+        LOG("%s: fseek(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    return 0;
+}
diff --git a/src/section/data.c b/src/section/data.c
new file mode 100644
index 0000000..6ea12d6
--- /dev/null
+++ b/src/section/data.c
@@ -0,0 +1,18 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nanowasm/nw.h>
+#include <nw/sections.h>
+#include <nw/types.h>
+
+int section_data_check(const struct section *const s, struct nw_mod *const m,
+    const unsigned long len)
+{
+    return -1;
+}
diff --git a/src/section/element.c b/src/section/element.c
new file mode 100644
index 0000000..39bd5b7
--- /dev/null
+++ b/src/section/element.c
@@ -0,0 +1,17 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/sections.h>
+#include <nanowasm/nw.h>
+
+int section_element_check(const struct section *const s,
+    struct nw_mod *const m, const unsigned long len)
+{
+    return -1;
+}
diff --git a/src/section/export.c b/src/section/export.c
new file mode 100644
index 0000000..0948067
--- /dev/null
+++ b/src/section/export.c
@@ -0,0 +1,161 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/sections.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+
+static int check_string(FILE *const f)
+{
+    varuint32 len;
+
+    if (varuint32_read(f, &len))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+
+    for (varuint32 i = 0; i < len; i++)
+    {
+        uint8_t byte;
+
+        if (!fread(&byte, sizeof byte, 1, f))
+        {
+            LOG("%s: fread(3) failed, feof=%d, ferror=%d\n",
+                __func__, feof(f), ferror(f));
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+static int check_kind(FILE *const f)
+{
+    uint8_t kind;
+
+    if (!fread(&kind, sizeof kind, 1, f))
+    {
+        LOG("%s: fread(3) failed: feof=%d, ferror=%d\n", __func__,
+            feof(f), ferror(f));
+        return -1;
+    }
+
+    return 0;
+}
+
+static int check_index(FILE *const f)
+{
+    varuint32 index;
+
+    if (varuint32_read(f, &index))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+static int check_export_entry(FILE *const f)
+{
+    if (check_string(f))
+    {
+        LOG("%s: check_string failed\n", __func__);
+        return -1;
+    }
+    else if (check_kind(f))
+    {
+        LOG("%s: check_kind failed\n", __func__);
+        return -1;
+    }
+    else if (check_index(f))
+    {
+        LOG("%s: check_index failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+static int check(FILE *const f, const unsigned long len)
+{
+    const long start = ftell(f);
+    varuint32 count;
+
+    if (start < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+    else if (varuint32_read(f, &count))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+
+    for (varuint32 i = 0; i < count; i++)
+        if (check_export_entry(f))
+        {
+            LOG("%s: check_export_entry failed\n", __func__);
+            return -1;
+        }
+
+    const long end = ftell(f);
+
+    if (end < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    const unsigned long size = end - start;
+
+    if (size != len)
+    {
+        LOG("%s: size exceeded (%lu expected, got %lu)\n",
+                __func__, len, size);
+        return -1;
+    }
+
+    return 0;
+}
+
+int section_export_check(const struct section *const s, struct nw_mod *const m,
+    const unsigned long len)
+{
+    FILE *const f = s->f;
+
+    if (m->sections.export)
+    {
+        LOG("%s: ignoring duplicate section\n", __func__);
+        return fseek(f, len, SEEK_CUR);
+    }
+
+    const long offset = ftell(f);
+
+    if (offset < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+    else if (check(f, len))
+    {
+        LOG("%s: check failed\n", __func__);
+        return -1;
+    }
+
+    m->sections.export = offset;
+    return 0;
+}
diff --git a/src/section/function.c b/src/section/function.c
new file mode 100644
index 0000000..3ffed36
--- /dev/null
+++ b/src/section/function.c
@@ -0,0 +1,127 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/sections.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <errno.h>
+#include <limits.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+
+static int run(FILE *const f, const varuint32 idx,
+    struct section_function *const out)
+{
+    varuint32 count;
+
+    if (varuint32_read(f, &count))
+    {
+        LOG("%s: varuint32_read count failed\n", __func__);
+        return -1;
+    }
+    else if (count > ULONG_MAX - 1)
+    {
+        fprintf(stderr, "%s: count overflow\n", __func__);
+        return -1;
+    }
+
+    for (varuint32 i = 0; i < count; i++)
+    {
+        varuint32 type;
+
+        if (varuint32_read(f, &type))
+        {
+            LOG("%s: varuint32_read type failed\n", __func__);
+            return -1;
+        }
+        else if (out && i == idx)
+        {
+            out->type = type;
+            out->nreturn = count;
+            return 0;
+        }
+    }
+
+    if (out)
+    {
+        LOG("%s: could not find function index %ju\n", __func__,
+            (uintmax_t)idx);
+        return -1;
+    }
+
+    return 0;
+}
+
+int section_function_check(const struct section *const s,
+    struct nw_mod *const m, const unsigned long len)
+{
+    FILE *const f = s->f;
+
+    if (m->sections.function)
+    {
+        LOG("%s: ignoring duplicate section\n", __func__);
+        return fseek(f, len, SEEK_CUR);
+    }
+
+    const long start = ftell(f);
+
+    if (start < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+    else if (run(f, 0, NULL))
+    {
+        LOG("%s: run failed\n", __func__);
+        return -1;
+    }
+
+    const long end = ftell(f);
+
+    if (end < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    const unsigned long size = end - start;
+
+    if (size != len)
+    {
+        LOG("%s: size exceeded (%lu expected, got %lu)\n",
+                __func__, len, size);
+        return -1;
+    }
+
+    m->sections.function = start;
+    return 0;
+}
+
+int section_function(const struct section *const s,
+    const struct nw_mod *const m, const varuint32 idx,
+    struct section_function *const f)
+{
+    const long offset = m->sections.function;
+
+    if (offset <= 0)
+    {
+        LOG("%s: function section not found", __func__);
+        return -1;
+    }
+    else if (fseek(s->f, offset, SEEK_SET))
+    {
+        LOG("%s: fseek(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    return run(s->f, idx, f);
+}
diff --git a/src/section/global.c b/src/section/global.c
new file mode 100644
index 0000000..eff2e0b
--- /dev/null
+++ b/src/section/global.c
@@ -0,0 +1,346 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/sections.h>
+#include <nanowasm/nw.h>
+#include <nw/interp.h>
+#include <nw/types.h>
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+
+struct global_type
+{
+    bool mutable;
+    enum value_type type;
+
+    union global_value
+    {
+        int32_t i32;
+        int64_t i64;
+        float f32;
+        double f64;
+    } value;
+};
+
+static int get_i32(const struct nw_interp *const i,
+    union global_value *const value)
+{
+    if (i->stack_i != sizeof value->i32)
+    {
+        LOG("%s: expected %zu used stack bytes, got %zu\n",
+            __func__, i->stack_i, sizeof value->i32);
+        return -1;
+    }
+
+    value->i32 = *(const int32_t *)i->cfg.stack.buf;
+    return 0;
+}
+
+static int get_i64(const struct nw_interp *const i,
+    union global_value *const value)
+{
+    if (i->stack_i != sizeof value->i64)
+    {
+        LOG("%s: expected %zu used stack bytes, got %zu\n",
+            __func__, i->stack_i, sizeof value->i64);
+        return -1;
+    }
+
+    value->i64 = *(const int64_t *)i->cfg.stack.buf;
+    return 0;
+}
+
+static int get_f32(const struct nw_interp *const i,
+    union global_value *const value)
+{
+    if (i->stack_i != sizeof value->f32)
+    {
+        LOG("%s: expected %zu used stack bytes, got %zu\n",
+            __func__, i->stack_i, sizeof value->f32);
+        return -1;
+    }
+
+    value->f32 = *(const float *)i->cfg.stack.buf;
+    return 0;
+}
+
+static int get_f64(const struct nw_interp *const i,
+    union global_value *const value)
+{
+    if (i->stack_i != sizeof value->f64)
+    {
+        LOG("%s: expected %zu used stack bytes, got %zu\n",
+            __func__, i->stack_i, sizeof value->f64);
+        return -1;
+    }
+
+    value->f64 = *(const double *)i->cfg.stack.buf;
+    return 0;
+}
+
+static int get_value(const struct nw_interp *const i,
+    const enum value_type type, union global_value *const value)
+{
+    static int (*const get[])(const struct nw_interp *, union global_value *) =
+    {
+        [VALUE_TYPE_I32] = get_i32,
+        [VALUE_TYPE_I64] = get_i64,
+        [VALUE_TYPE_F32] = get_f32,
+        [VALUE_TYPE_F64] = get_f64
+    };
+
+    if (get[type](i, value))
+    {
+        LOG("%s: get failed with type %d\n", __func__, type);
+        return -1;
+    }
+
+    return 0;
+}
+
+static int check_global_type(FILE *const f, struct global_type *const g)
+{
+    const struct nw_interp_cfg cfg =
+    {
+        .stack = NW_BUF(sizeof (union global_value))
+    };
+
+    struct nw_interp i;
+    enum value_type vtype;
+    varint7 content_type;
+    varuint1 mutability;
+    union global_value value;
+
+    if (varint7_read(f, &content_type))
+    {
+        LOG("%s: varint7_read failed\n", __func__);
+        return -1;
+    }
+    else if (get_value_type(content_type, &vtype))
+    {
+        LOG("%s: get_value_type failed\n", __func__);
+        return -1;
+    }
+    else if (varuint1_read(f, &mutability))
+    {
+        LOG("%s: varuint1_read failed\n", __func__);
+        return -1;
+    }
+    else if (interp_start(&cfg, f, &i))
+    {
+        LOG("%s: interp_start failed\n", __func__);
+        return -1;
+    }
+    else if (interp_run_limited(&i, &interp_initexpr_set))
+    {
+        LOG("%s: interp_run failed\n", __func__);
+        return -1;
+    }
+    else if (get_value(&i, vtype, &value))
+    {
+        LOG("%s: get_value failed\n", __func__);
+        return -1;
+    }
+
+    *g = (const struct global_type)
+    {
+        .mutable = mutability,
+        .type = vtype,
+        .value = value
+    };
+
+    return 0;
+}
+
+static int set_i32(struct nw_interp *const i, void *const dst,
+    const struct global_type *const g)
+{
+    *(int32_t *)dst = g->value.i32;
+    return 0;
+}
+
+static int set_i64(struct nw_interp *const i, void *const dst,
+    const struct global_type *const g)
+{
+    *(int64_t *)dst = g->value.i64;
+    return 0;
+}
+
+static int set_f32(struct nw_interp *const i, void *const dst,
+    const struct global_type *const g)
+{
+    *(float *)dst = g->value.f32;
+    return 0;
+}
+
+static int set_f64(struct nw_interp *const i, void *const dst,
+    const struct global_type *const g)
+{
+    *(double *)dst = g->value.f64;
+    return 0;
+}
+
+static int add_global(struct nw_interp *const i,
+    const struct global_type *const g)
+{
+    const struct nw_gframe f =
+    {
+        .mutable = g->mutable,
+        .type = g->type
+    };
+
+    const size_t sz = sizeof f + get_type_size(g->type),
+        max = i->cfg.global.n;
+
+    if (max < sz || i->global_i > max - sz)
+    {
+        LOG("%s: global memory overflow\n", __func__);
+        i->exception = "global memory overflow";
+        return -1;
+    }
+
+    void *const buf = (char *)i->cfg.global.buf + i->global_i;
+    struct nw_gframe *const dst = buf;
+
+    if (i->gfp)
+        i->gfp->next = dst;
+
+    *dst = f;
+
+    static int (*const set[])(struct nw_interp *, void *,
+        const struct global_type *) =
+    {
+        [VALUE_TYPE_I32] = set_i32,
+        [VALUE_TYPE_I64] = set_i64,
+        [VALUE_TYPE_F32] = set_f32,
+        [VALUE_TYPE_F64] = set_f64
+    };
+
+    if (set[g->type](i, dst + 1, g))
+    {
+        LOG("%s: set failed with type %d\n", __func__, g->type);
+        return -1;
+    }
+
+    i->global_i += sz;
+    i->gfp = dst;
+    return 0;
+}
+
+static int check_global_types(FILE *const f,
+    struct nw_interp *const in)
+{
+    varuint32 count;
+
+    if (varuint32_read(f, &count))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+
+    for (varuint32 i = 0; i < count; i++)
+    {
+        struct global_type g;
+
+        if (check_global_type(f, &g))
+        {
+            LOG("%s: check_global_type\n", __func__);
+            return -1;
+        }
+        else if (in && add_global(in, &g))
+        {
+            LOG("%s: add_global failed\n", __func__);
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+static int check(FILE *const f, const unsigned long len)
+{
+    const long start = ftell(f);
+
+    if (start < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+    else if (check_global_types(f, NULL))
+    {
+        LOG("%s: check_global_types failed\n", __func__);
+        return -1;
+    }
+
+    const long end = ftell(f);
+
+    if (end < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    const unsigned long size = end - start;
+
+    if (size != len)
+    {
+        LOG("%s: size exceeded (%lu expected, got %lu)\n",
+            __func__, len, size);
+        return -1;
+    }
+
+    return 0;
+}
+
+int section_global_check(const struct section *const s, struct nw_mod *const m,
+    const unsigned long len)
+{
+    FILE *const f = s->f;
+
+    if (m->sections.global)
+    {
+        LOG("%s: ignoring duplicate section\n", __func__);
+        return fseek(f, len, SEEK_CUR);
+    }
+
+    const long offset = ftell(f);
+
+    if (offset < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+    else if (check(f, len))
+    {
+        LOG("%s: check failed\n", __func__);
+        return -1;
+    }
+
+    m->sections.global = offset;
+    return 0;
+}
+
+int section_global_push(FILE *const f, const struct nw_mod *const m,
+    struct nw_interp *const i)
+{
+    if (fseek(f, m->sections.global, SEEK_SET))
+    {
+        LOG("%s: fseek(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+    else if (check_global_types(f, i))
+    {
+        LOG("%s: check_global_types failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
diff --git a/src/section/import.c b/src/section/import.c
new file mode 100644
index 0000000..5dd708e
--- /dev/null
+++ b/src/section/import.c
@@ -0,0 +1,274 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/sections.h>
+#include <nw/fstring.h>
+#include <nw/log.h>
+#include <nw/types.h>
+#include <errno.h>
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+static int dump_import_name(FILE *const f, const varuint32 len)
+{
+    for (varuint32 i = 0; i < len; i++)
+    {
+        uint8_t byte;
+
+        if (!fread(&byte, sizeof byte, 1, f))
+        {
+            LOG("%s: fread(3) failed, feof=%d, ferror=%d\n",
+                __func__, feof(f), ferror(f));
+            return -1;
+        }
+
+        LOG("%c", (char)byte);
+    }
+
+    return 0;
+}
+
+static int check_module_string(const struct nw_mod_cfg *const cfg,
+    FILE *const f)
+{
+    varuint32 len;
+
+    if (varuint32_read(f, &len))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+
+    for (size_t i = 0; i < cfg->n_imports; i++)
+    {
+        const struct nw_import *const im = &cfg->imports[i];
+        const char *const mod = im->module;
+
+        if (strlen(mod) == len)
+        {
+            const long offset = ftell(f);
+
+            if (offset < 0)
+            {
+                LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+                return -1;
+            }
+            else if (!fstrcmp(mod, f, true))
+                return 0;
+            else if (fseek(f, offset, SEEK_SET))
+            {
+                LOG("%s: fseek(3): %s\n", __func__, strerror(errno));
+                return -1;
+            }
+        }
+    }
+
+    LOG("%s: required imported module ", __func__);
+    dump_import_name(f, len);
+    LOG(" not found\n");
+    return -1;
+}
+
+static int check_field_string(const struct nw_mod_cfg *const cfg,
+    FILE *const f)
+{
+    varuint32 len;
+
+    if (varuint32_read(f, &len))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+
+    for (size_t i = 0; i < cfg->n_imports; i++)
+    {
+        const struct nw_import *const im = &cfg->imports[i];
+        const char *const field = im->field;
+
+        if (strlen(field) == len)
+        {
+            const long offset = ftell(f);
+
+            if (offset < 0)
+            {
+                LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+                return -1;
+            }
+            else if (!fstrcmp(field, f, true))
+                return 0;
+            else if (fseek(f, offset, SEEK_SET))
+            {
+                LOG("%s: fseek(3): %s\n", __func__, strerror(errno));
+                return -1;
+            }
+        }
+    }
+
+    LOG("%s: required imported field ", __func__);
+    dump_import_name(f, len);
+    LOG(" not found\n");
+    return -1;
+}
+
+static int check_function_kind(FILE *const f)
+{
+    varuint32 type;
+
+    if (varuint32_read(f, &type))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+static int check_table_kind(FILE *const f)
+{
+    varint7 type;
+
+    if (varint7_read(f, &type))
+    {
+        LOG("%s: varint7_read failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+static int check_memory_kind(FILE *const f)
+{
+    /* TODO. */
+    return -1;
+}
+
+static int check_global_kind(FILE *const f)
+{
+    /* TODO. */
+    return -1;
+}
+
+static int check_import_entry(const struct nw_mod_cfg *const cfg,
+    FILE *const f)
+{
+    if (check_module_string(cfg, f))
+    {
+        LOG("%s: check_module_string failed\n", __func__);
+        return -1;
+    }
+    else if (check_field_string(cfg, f))
+    {
+        LOG("%s: check_field_string failed\n", __func__);
+        return -1;
+    }
+
+    uint8_t kind;
+
+    if (!fread(&kind, sizeof kind, 1, f))
+    {
+        LOG("%s: fread(3) failed, feof=%d, ferror=%d\n",
+            __func__, feof(f), ferror(f));
+        return -1;
+    }
+
+    static int (*const fn[])(FILE *) =
+    {
+        [NW_KIND_FUNCTION] = check_function_kind,
+        [NW_KIND_TABLE] = check_table_kind,
+        [NW_KIND_MEMORY] = check_memory_kind,
+        [NW_KIND_GLOBAL] = check_global_kind
+    };
+
+    if (kind >= sizeof fn / sizeof *fn)
+    {
+        LOG("%s: unexpected kind %#" PRIx8 "\n", __func__, kind);
+        return -1;
+    }
+
+    return fn[kind](f);
+}
+
+static int check(const struct nw_mod_cfg *const cfg, FILE *const f,
+    const unsigned long len)
+{
+    const long start = ftell(f);
+
+    if (start < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    varuint32 count;
+
+    if (varuint32_read(f, &count))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+
+    for (varuint32 i = 0; i < count; i++)
+        if (check_import_entry(cfg, f))
+        {
+            LOG("%s: check_import_entry failed\n", __func__);
+            return -1;
+        }
+
+    const long end = ftell(f);
+
+    if (end < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    const unsigned long size = end - start;
+
+    if (size != len)
+    {
+        LOG("%s: size exceeded (%lu expected, got %lu)\n",
+                __func__, len, size);
+        return -1;
+    }
+
+    return 0;
+}
+
+int section_import_check(const struct section *const s, struct nw_mod *m,
+    const unsigned long len)
+{
+    const struct nw_mod_cfg *const cfg = s->cfg;
+    FILE *const f = s->f;
+
+    if (m->sections.import)
+    {
+        LOG("%s: ignoring duplicate section\n", __func__);
+        return fseek(f, len, SEEK_CUR);
+    }
+
+    const long offset = ftell(f);
+
+    if (offset < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+    else if (check(cfg, f, len))
+    {
+        LOG("%s: check failed\n", __func__);
+        return -1;
+    }
+
+    m->sections.import = offset;
+    return 0;
+}
diff --git a/src/section/memory.c b/src/section/memory.c
new file mode 100644
index 0000000..0de5b4c
--- /dev/null
+++ b/src/section/memory.c
@@ -0,0 +1,102 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/sections.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+
+static int check_memory_type(FILE *const f, struct resizable_limits *const r)
+{
+    return check_resizable_limits(f, r);
+}
+
+static int check(FILE *const f, const unsigned long len,
+    struct resizable_limits *const r)
+{
+    const long start = ftell(f);
+
+    if (start < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    varuint32 count;
+
+    if (varuint32_read(f, &count))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return 1;
+    }
+    else if (count > 1)
+    {
+        LOG("%s: only 1 memory allowed\n", __func__);
+        return 1;
+    }
+
+    for (varuint32 i = 0; i < count; i++)
+        if (check_memory_type(f, r))
+        {
+            LOG("%s: check_memory_type failed\n", __func__);
+            return -1;
+        }
+
+    const long end = ftell(f);
+
+    if (end < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    const unsigned long size = end - start;
+
+    if (size != len)
+    {
+        LOG("%s: size exceeded (%lu expected, got %lu)\n",
+                __func__, len, size);
+        return -1;
+    }
+
+    return 0;
+}
+
+int section_memory_check(const struct section *const s, struct nw_mod *const m,
+    const unsigned long len)
+{
+    FILE *const f = s->f;
+
+    if (m->sections.memory)
+    {
+        LOG("%s: ignoring duplicate section\n", __func__);
+        return fseek(f, len, SEEK_CUR);
+    }
+
+    const long offset = ftell(f);
+    struct resizable_limits r;
+
+    if (offset < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+    else if (check(f, len, &r))
+    {
+        LOG("%s: check failed\n", __func__);
+        return -1;
+    }
+
+    m->heap_len = r.sz;
+    m->sections.memory = offset;
+    return 0;
+}
diff --git a/src/section/start.c b/src/section/start.c
new file mode 100644
index 0000000..dd44652
--- /dev/null
+++ b/src/section/start.c
@@ -0,0 +1,18 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/sections.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+
+int section_start_check(const struct section *const s, struct nw_mod *const m,
+    const unsigned long len)
+{
+    return -1;
+}
diff --git a/src/section/table.c b/src/section/table.c
new file mode 100644
index 0000000..15fc619
--- /dev/null
+++ b/src/section/table.c
@@ -0,0 +1,112 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/sections.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+
+static int check_table_type(FILE *const f)
+{
+    enum {ANYFUNC = 0x70};
+    varint7 elem_type;
+
+    if (varint7_read(f, &elem_type))
+    {
+        LOG("%s: varint7_read failed\n", __func__);
+        return -1;
+    }
+    else if (elem_type != ANYFUNC)
+    {
+        LOG("%s: expected %x, got %x", __func__, ANYFUNC,
+            (int)elem_type);
+        return -1;
+    }
+
+    /* TODO: what to do with this? */
+    struct resizable_limits r;
+
+    return check_resizable_limits(f, &r);
+}
+
+static int check(FILE *const f, const unsigned long len)
+{
+    const long start = ftell(f);
+
+    if (start < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    varuint32 count;
+
+    if (varuint32_read(f, &count))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+
+    for (varuint32 i = 0; i < count; i++)
+        if (check_table_type(f))
+        {
+            LOG("%s: check_table_type failed\n", __func__);
+            return -1;
+        }
+
+    const long end = ftell(f);
+
+    if (end < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    const unsigned long size = end - start;
+
+    if (size != len)
+    {
+        LOG("%s: size exceeded (%lu expected, got %lu)\n",
+                __func__, len, size);
+        return -1;
+    }
+
+    return 0;
+}
+
+int section_table_check(const struct section *const s, struct nw_mod *const m,
+    const unsigned long len)
+{
+    FILE *const f = s->f;
+
+    if (m->sections.table)
+    {
+        LOG("%s: ignoring duplicate section\n", __func__);
+        return fseek(f, len, SEEK_CUR);
+    }
+
+    const long offset = ftell(f);
+
+    if (offset < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+    else if (check(f, len))
+    {
+        LOG("%s: check failed\n", __func__);
+        return -1;
+    }
+
+    m->sections.table = offset;
+    return 0;
+}
diff --git a/src/section/type.c b/src/section/type.c
new file mode 100644
index 0000000..0bf7a06
--- /dev/null
+++ b/src/section/type.c
@@ -0,0 +1,180 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/log.h>
+#include <nw/sections.h>
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+
+static int check_value_type(FILE *const f, enum value_type *const vtype)
+{
+    varint7 value_type;
+
+    if (varint7_read(f, &value_type))
+    {
+        LOG("%s: varint7_read failed\n", __func__);
+        return -1;
+    }
+    else if (vtype && get_value_type(value_type, vtype))
+    {
+        LOG("%s: get_value_type failed\n", __func__);
+        return -1;
+    }
+
+    return 0;
+}
+
+static int check_func_type(FILE *const f, struct retval *const r)
+{
+    varint7 form;
+    varuint32 param_count;
+
+    if (varint7_read(f, &form))
+    {
+        LOG("%s: varint7_read failed\n", __func__);
+        return -1;
+    }
+    else if (varuint32_read(f, &param_count))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+
+    for (varuint32 i = 0; i < param_count; i++)
+        if (check_value_type(f, NULL))
+        {
+            LOG("%s: check_value_type failed\n", __func__);
+            return -1;
+        }
+
+    varuint1 return_count;
+    enum value_type vtype;
+
+    if (varuint1_read(f, &return_count))
+    {
+        LOG("%s: varuint1_read failed\n", __func__);
+        return -1;
+    }
+    else if (return_count && check_value_type(f, &vtype))
+    {
+        LOG("%s: check_value_type 2 failed\n", __func__);
+        return -1;
+    }
+
+    *r = (const struct retval)
+    {
+        .returns = return_count,
+        .type = vtype
+    };
+
+    return 0;
+}
+
+static int run(FILE *const f, const unsigned long len, const varuint32 idx,
+    struct nw_frame *const fr)
+{
+    const long start = ftell(f);
+    varuint32 count;
+
+    if (start < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+    else if (varuint32_read(f, &count))
+    {
+        LOG("%s: varuint32_read failed\n", __func__);
+        return -1;
+    }
+
+    for (varuint32 i = 0; i < count; i++)
+    {
+        struct retval r;
+
+        if (check_func_type(f, &r))
+        {
+            LOG("%s: check_func_type failed\n", __func__);
+            return -1;
+        }
+        else if (fr && i == idx)
+        {
+            fr->retval = r;
+            return 0;
+        }
+    }
+
+    const long end = ftell(f);
+
+    if (end < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    const unsigned long size = end - start;
+
+    if (size != len)
+    {
+        LOG("%s: size exceeded (%lu expected, got %lu)\n",
+                __func__, len, size);
+        return -1;
+    }
+
+    return 0;
+}
+
+int section_type_check(const struct section *const s, struct nw_mod *const m,
+    const unsigned long len)
+{
+    FILE *const f = s->f;
+
+    if (m->sections.type)
+    {
+        LOG("%s: ignoring duplicate section\n", __func__);
+        return fseek(f, len, SEEK_CUR);
+    }
+
+    const long offset = ftell(f);
+
+    if (offset < 0)
+    {
+        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+    else if (run(f, len, 0, NULL))
+    {
+        LOG("%s: check failed\n", __func__);
+        return -1;
+    }
+
+    m->sections.type = offset;
+    return 0;
+}
+
+int section_type_push(FILE *const f, const struct nw_mod *const m,
+    const varuint32 idx, struct nw_frame *const fr)
+{
+    const long offset = m->sections.type;
+
+    if (offset <= 0)
+    {
+        LOG("%s: function section not found", __func__);
+        return -1;
+    }
+    else if (fseek(f, offset, SEEK_SET))
+    {
+        LOG("%s: fseek(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    return run(f, 0, idx, fr);
+}
diff --git a/src/start.c b/src/start.c
new file mode 100644
index 0000000..c22bddf
--- /dev/null
+++ b/src/start.c
@@ -0,0 +1,81 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nanowasm/nw.h>
+#include <nw/interp.h>
+#include <nw/log.h>
+#include <nw/search.h>
+#include <nw/sections.h>
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+
+int nw_start(const struct nw_inst_cfg *const icfg, struct nw_inst *const i)
+{
+    int ret = -1;
+    const struct nw_mod *const m = icfg->interp.m;
+    const struct nw_mod_cfg *const mcfg = &m->cfg;
+    FILE *const f = fopen(mcfg->path, "rb");
+    struct search_fn fn;
+    struct nw_frame fr = {0};
+
+    *i = (const struct nw_inst){0};
+
+    if (!f)
+    {
+        LOG("%s: fopen(3) %s: %s\n", __func__, mcfg->path, strerror(errno));
+        goto end;
+    }
+    else if (m->sections.start)
+    {
+        /* TODO. */
+    }
+    else if (interp_start(&icfg->interp, f, &i->interp))
+    {
+        LOG("%s: interp_start failed\n", __func__);
+        goto end;
+    }
+    else if (search_exported_fn("_start", m, f, &fn))
+    {
+        LOG("%s: search_exported_fn failed\n", __func__);
+        goto end;
+    }
+    else if (section_global_push(f, m, &i->interp))
+    {
+        LOG("%s: section_global_push failed\n", __func__);
+        goto end;
+    }
+    else if (section_type_push(f, m, fn.index, &fr))
+    {
+        LOG("%s: section_type_push failed\n", __func__);
+        goto end;
+    }
+    else if (section_code_push(f, fn.start, &fr))
+    {
+        LOG("%s: section_code_push failed\n", __func__);
+        goto end;
+    }
+    else if (interp_push(&i->interp, &fr))
+    {
+        LOG("%s: interp_push failed\n", __func__);
+        goto end;
+    }
+
+    ret = 0;
+
+end:
+
+    if (ret && f && fclose(f))
+    {
+        LOG("%s: fclose(3) %s: %s\n", __func__, mcfg->path, strerror(errno));
+        ret = -1;
+    }
+
+    return ret;
+}
diff --git a/src/stop.c b/src/stop.c
new file mode 100644
index 0000000..1d5d604
--- /dev/null
+++ b/src/stop.c
@@ -0,0 +1,27 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nanowasm/nw.h>
+#include <nw/log.h>
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+
+int nw_stop(struct nw_inst *const i)
+{
+    struct nw_interp *const in = &i->interp;
+
+    if (in->f && fclose(in->f))
+    {
+        LOG("%s: fclose(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    return 0;
+}
diff --git a/src/types.c b/src/types.c
new file mode 100644
index 0000000..88c883e
--- /dev/null
+++ b/src/types.c
@@ -0,0 +1,89 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/leb128.h>
+#include <nw/types.h>
+#include <stdio.h>
+
+int varuint1_read(FILE *const f, varuint1 *const out)
+{
+    unsigned long long value;
+
+    if (leb128_read_unsigned(f, 1, &value))
+        return -1;
+
+    *out = value;
+    return 0;
+}
+
+int varint7_read(FILE *const f, varint7 *const out)
+{
+    long long value;
+
+    if (leb128_read_signed(f, 7, &value))
+        return -1;
+
+    *out = value;
+    return 0;
+}
+
+int varuint7_read(FILE *const f, varuint7 *const out)
+{
+    unsigned long long value;
+
+    if (leb128_read_unsigned(f, 7, &value))
+        return -1;
+
+    *out = value;
+    return 0;
+}
+
+int varuint32_read(FILE *const f, varuint32 *out)
+{
+    unsigned long long value;
+
+    if (leb128_read_unsigned(f, 32, &value))
+        return -1;
+
+    *out = value;
+    return 0;
+}
+
+int varint32_read(FILE *const f, varint32 *const out)
+{
+    long long value;
+
+    if (leb128_read_signed(f, 32, &value))
+        return -1;
+
+    *out = value;
+    return 0;
+}
+
+int varuint64_read(FILE *const f, varuint64 *const out)
+{
+    unsigned long long value;
+
+    if (leb128_read_unsigned(f, 64, &value))
+        return -1;
+
+    *out = value;
+    return 0;
+}
+
+int varint64_read(FILE *const f, varint64 *const out)
+{
+    long long value;
+
+    if (leb128_read_signed(f, 64, &value))
+        return -1;
+
+    *out = value;
+    return 0;
+}
diff --git a/src/unload.c b/src/unload.c
new file mode 100644
index 0000000..5b5ef9b
--- /dev/null
+++ b/src/unload.c
@@ -0,0 +1,19 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nanowasm/nw.h>
+#include <nw/types.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+void nw_unload(struct nw_mod *const m)
+{
+    free(m);
+}
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
new file mode 100644
index 0000000..60ebec3
--- /dev/null
+++ b/test/CMakeLists.txt
@@ -0,0 +1,24 @@
+# nanowasm, a tiny WebAssembly/Wasm interpreter
+# Copyright (C) 2023-2024  Xavier Del Campo Romero
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+cmake_minimum_required(VERSION 3.18)
+project(test C)
+add_executable(${PROJECT_NAME} main.c)
+target_link_libraries(${PROJECT_NAME} PRIVATE nanowasm)
+
+include(CheckLinkerFlag)
+set(ldflags -Wl,--gc-sections)
+
+foreach(f ${ldflags})
+    string(REPLACE "-" "_" var supported_${f})
+    string(REPLACE "," "_" var ${var})
+    check_linker_flag(C ${f} ${var})
+
+    if(${var})
+        target_link_options(${PROJECT_NAME} PRIVATE ${f})
+    endif()
+endforeach()
diff --git a/test/example.wasm b/test/example.wasm
new file mode 100755
index 0000000..afea5ed
--- /dev/null
+++ b/test/example.wasm
diff --git a/test/main.c b/test/main.c
new file mode 100644
index 0000000..70cacd8
--- /dev/null
+++ b/test/main.c
@@ -0,0 +1,105 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2024  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nanowasm/nw.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static int proc_exit(const struct nw_args *const params,
+    union nw_value *const ret, void *const user)
+{
+    return -1;
+}
+
+int main(int argc, char *argv[])
+{
+    static const struct nw_import imports[] =
+    {
+        {
+            .kind = NW_KIND_FUNCTION,
+            .module = "wasi_snapshot_preview1",
+            .field = "proc_exit",
+            .u.function =
+            {
+                .signature = "i32()",
+                .fn = proc_exit
+            }
+        }
+    };
+
+    static const struct nw_mod_cfg cfg =
+    {
+        .path = "example.wasm",
+        .imports = imports,
+        .n_imports = sizeof imports / sizeof *imports
+    };
+
+    struct nw_mod m;
+
+    if (nw_load(&cfg, &m))
+    {
+        fprintf(stderr, "%s: nw_load failed\n", __func__);
+        return EXIT_FAILURE;
+    }
+
+    const struct nw_inst_cfg icfg =
+    {
+        .interp =
+        {
+            .stack = NW_BUF(256),
+            .heap = NW_BUF(2048),
+            .global = NW_BUF(24),
+            .m = &m
+        }
+    };
+
+    struct nw_inst inst;
+
+    if (nw_start(&icfg, &inst))
+    {
+        fprintf(stderr, "%s: nw_start failed\n", __func__);
+        return EXIT_FAILURE;
+    }
+
+    const union nw_inst_state *s = &inst.state;
+    int ret = EXIT_FAILURE;
+
+again:
+
+    switch (nw_run(&inst))
+    {
+        case NW_STATE_AGAIN:
+            goto again;
+
+        case NW_STATE_RETURNED:
+            fprintf(stderr, "instance returned %ld\n", s->retval);
+            break;
+
+        case NW_STATE_EXCEPTION:
+            fprintf(stderr, "exception: %s\n", s->exception);
+            goto end;
+
+        case NW_STATE_FATAL:
+            goto end;
+    }
+
+    ret = EXIT_SUCCESS;
+
+end:
+
+    if (nw_stop(&inst))
+    {
+        fprintf(stderr, "%s: nw_stop failed\n", __func__);
+        ret = EXIT_FAILURE;
+    }
+
+    return ret;
+}