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| author | JF Bastien <github@jfbastien.com> | 2017-05-25 15:19:15 -0700 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2017-05-25 15:19:15 -0700 |
| commit | 0e0e3908afed0def00a8bd86982aee1cc2310b5e (patch) | |
| tree | 45aa1e01391a5385868c156bbd2ead9025489b44 /FutureFeatures.md | |
| parent | 26c7b4a2481ec31a0107bfa29cba811ca9be646b (diff) | |
| download | nanowasm-design-0e0e3908afed0def00a8bd86982aee1cc2310b5e.tar.gz | |
Move exception handling
Now tracked by: #1078
As discussed here: #1066
Diffstat (limited to 'FutureFeatures.md')
| -rw-r--r-- | FutureFeatures.md | 44 |
1 files changed, 7 insertions, 37 deletions
diff --git a/FutureFeatures.md b/FutureFeatures.md index 58cd2ab..95ea898 100644 --- a/FutureFeatures.md +++ b/FutureFeatures.md @@ -9,15 +9,17 @@ issues. ## Tracking Issues -| Feature | Tracking issue | Status | -|------------------|----------------|-------------| -| Specification | [1077][] | in progress | -| Threads | [1073][] | in progress | -| Fixed-width SIMD | [1075][] | in progress | +| Feature | Tracking issue | Status | +|--------------------|----------------|-------------| +| Specification | [1077][] | in progress | +| Threads | [1073][] | in progress | +| Fixed-width SIMD | [1075][] | in progress | +| Exception handling | [1078][] | in progress | [1073]: https://github.com/WebAssembly/design/issues/1073 [1075]: https://github.com/WebAssembly/design/issues/1075 [1077]: https://github.com/WebAssembly/design/issues/1077 + [1078]: https://github.com/WebAssembly/design/issues/1078 ## Legacy Future Features @@ -34,38 +36,6 @@ the [MVP](MVP.md). This is covered in the [tooling](Tooling.md) section. -### Zero-cost Exception Handling -#### :star: - -The WebAssembly MVP may support four no-exception -modes for C++: - -* Compiler transforms `throw` to `abort()`. -* Compiler-enforced `-fno-exceptions` mode (note [caveats][]). -* Compiler conversion of exceptions to branching at all callsites. -* In a Web environment exception handling can be emulated using JavaScript - exception handling, which can provide correct semantics but isn't fast. - -These modes are suboptimal for code bases which rely on C++ exception handling, -but are perfectly acceptable for C code, or for C++ code which avoids -exceptions. This doesn't prevent developers from using the C++ standard library: -their code will function correctly (albeit slower at times) as long as it -doesn't encounter exceptional cases. - -Post-MVP, WebAssembly will gain support for developer access to stack unwinding, -inspection, and limited manipulation. These are critical to supporting zero-cost -exception handling by exposing [low-level capabilities][]. - -In turn, stack unwinding, inspection, and limited manipulation will be used to -implement `setjmp`/`longjmp`. This can enable all of the defined behavior of -`setjmp`/`longjmp`, namely unwinding the stack without calling C++ -destructors. It does not, however, allow the undefined behavior case of jumping -forward to a stack that was already unwound which is sometimes used to implement -coroutines. Coroutine support is being -[considered separately](FutureFeatures.md#coroutines). - - [caveats]: https://blog.mozilla.org/nnethercote/2011/01/18/the-dangers-of-fno-exceptions - [low-level capabilities]: https://extensiblewebmanifesto.org ### Feature Testing #### :star: |