Move signal handling to processes

So far, libweb installed a signal handler so as to handle SIGTERM,
SIGPIPE and SIGINT signals so that processes would not have to care
about such details.

However, it is not advisable for libraries to install signal handlers,
as signals are handled on a per-process basis. The previous approach
would be incompatible if several instances of the library were allocated
by the same process.

Unfortunately, this has the undesired side effect of adding the
boilerplate code into the process.

1 files changed, 70 insertions, 7 deletions

diff --git a/examples/hello/main.c b/examples/hello/main.c
index 62e2a9e..8ddf691 100644
--- a/examples/hello/main.c
+++ b/examples/hello/main.c
@@ -1,10 +1,21 @@
+/* As of FreeBSD 13.2, sigaction(2) still conforms to IEEE Std
+ * 1003.1-1990 (POSIX.1), which did not define SA_RESTART.
+ * FreeBSD supports it as an extension, but then _POSIX_C_SOURCE must
+ * not be defined. */
+#ifndef __FreeBSD__
+#define _POSIX_C_SOURCE 200809L
+#endif
+
 #include <dynstr.h>
 #include <libweb/handler.h>
 #include <libweb/html.h>
 #include <libweb/http.h>
+#include <errno.h>
+#include <signal.h>
 #include <stddef.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
 static int hello(const struct http_payload *const pl,
     struct http_response *const r, void *const user)
@@ -25,7 +36,7 @@ static int hello(const struct http_payload *const pl,
         fprintf(stderr, "%s: html_node_add_child body failed\n", __func__);
         goto end;
     }
-    else if (!(p = html_node_add_child(html, "p")))
+    else if (!(p = html_node_add_child(body, "p")))
     {
         fprintf(stderr, "%s: html_node_add_child p failed\n", __func__);
         goto end;
@@ -78,6 +89,59 @@ static int on_length(const unsigned long long len,
     return 1;
 }
 
+struct handler *handler;
+
+static void handle_signal(const int signum)
+{
+    switch (signum)
+    {
+        case SIGINT:
+            /* Fall through. */
+        case SIGTERM:
+            handler_notify_close(handler);
+            break;
+
+        default:
+            break;
+    }
+}
+
+static int init_signals(void)
+{
+    struct sigaction sa =
+    {
+        .sa_handler = handle_signal,
+        .sa_flags = SA_RESTART
+    };
+
+    sigemptyset(&sa.sa_mask);
+
+    static const struct signal
+    {
+        int signal;
+        const char *name;
+    } signals[] =
+    {
+        {.signal = SIGINT, .name = "SIGINT"},
+        {.signal = SIGTERM, .name = "SIGTERM"},
+        {.signal = SIGPIPE, .name = "SIGPIPE"}
+    };
+
+    for (size_t i = 0; i < sizeof signals / sizeof *signals; i++)
+    {
+        const struct signal *const s = &signals[i];
+
+        if (sigaction(s->signal, &sa, NULL))
+        {
+            fprintf(stderr, "%s: sigaction(2) %s: %s\n",
+                __func__, s->name, strerror(errno));
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
 int main(int argc, char *argv[])
 {
     int ret = EXIT_FAILURE;
@@ -86,17 +150,16 @@ int main(int argc, char *argv[])
         .length = on_length
     };
 
-    struct handler *const h = handler_alloc(&cfg);
     static const char *const urls[] = {"/", "/index.html"};
 
-    if (!h)
+    if (!(handler = handler_alloc(&cfg)))
     {
         fprintf(stderr, "%s: handler_alloc failed\n", __func__);
         goto end;
     }
 
     for (size_t i = 0; i < sizeof urls / sizeof *urls; i++)
-        if (handler_add(h, urls[i], HTTP_OP_GET, hello, NULL))
+        if (handler_add(handler, urls[i], HTTP_OP_GET, hello, NULL))
         {
             fprintf(stderr, "%s: handler_add failed\n", __func__);
             goto end;
@@ -104,7 +167,7 @@ int main(int argc, char *argv[])
 
     unsigned short outport;
 
-    if (handler_listen(h, 0, &outport))
+    if (handler_listen(handler, 0, &outport))
     {
         fprintf(stderr, "%s: handler_listen failed\n", __func__);
         goto end;
@@ -112,7 +175,7 @@ int main(int argc, char *argv[])
 
     printf("Listening on port %hu\n", outport);
 
-    if (handler_loop(h))
+    if (handler_loop(handler))
     {
         fprintf(stderr, "%s: handler_loop failed\n", __func__);
         goto end;
@@ -121,6 +184,6 @@ int main(int argc, char *argv[])
     ret = EXIT_SUCCESS;
 
 end:
-    handler_free(h);
+    handler_free(handler);
     return ret;
 }