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WebAssembly / wasm-c-api

Wasm C API prototype
Apache License 2.0
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Make `wasm_global_set` a safe API. #133

Closed sunfishcode closed 4 years ago

sunfishcode commented 4 years ago

Make wasm_global_set a safe API by allowing it to return a trap in error cases.

Traps in the wasm spec are used to report runtime errors, and the errors wasm_global_set reports are things that wasm would catch at validation time.

Nevertheless, using a trap here is consistent with the official JS API raising exceptions on the same conditions. And, it provides a message explaining the reason for the error.

To support users for whom mutablility and type checks are believed to be unacceptable overhead, add a wasm_global_set_unsafe function which skips those checks, at the penalty of undefined behavior.

sunfishcode commented 4 years ago

Note that this PR does not yet update the wasm-c.cc implementation or the C++ API, so it's not ready to be merged as-is. This just illustrates a change to the C API so that we can discuss it in detail.

rossberg commented 4 years ago

Let's perhaps reach a conclusion on issue #132 first? Personally, I still think this is not a natural or principled way to go about incorrect API usage in a language like C. Adding arbitrary one-off "unsafe" functions -- when everything is unsafe anyway -- kind of reenforces that point.

I don't think comparison to the JS API is particularly helpful, since that is (1) for a safe language and (2) not designed for efficiently building safer, more high-level API abstractions on top.

sunfishcode commented 4 years ago

Superseded by https://github.com/WebAssembly/wasm-c-api/pull/134.