WebAssembly C and C++ API

Work in progress! No docs yet.

Interfaces

• C API:

  • See example/*.c for example usages.

  • See include/wasm.h for interface.

• C++ API:

  • See example/*.cc for example usages.

  • See include/wasm.hh for interface.

Implementation

• A prototype implementation based on V8 is in src.

  • Note that this requires adding a module to V8, so it patches V8's build file.

• C API is implemented on top of C++ API.

• See Makefile for build recipe. Canonical steps to run examples:

  1. make v8-checkout
  2. make v8
  3. make all

Limitations

V8 implementation:

• Currently requires patching V8 by adding a module.

• Host functions (Func::make) create a JavaScript function internally, since V8 cannot handle raw C imports yet.

• As a consequence, does not support i64 in external calls or host functions.

• Also cannot handle multiple values in external calls or host functions.

• Host functions and host globals are created through auxiliary modules constructed on the fly, to work around limitations in JS API.

TODO

V8 implementation:

• Use reference counting and caching for types?

Possible API tweaks:

• Distinguish vec and own_vec in C++ API

• Handle constness of vectors properly in C API

• Find a way to perform C callbacks through C++ without extra wrapper?

• Add iterators to vec class?