Enable -fwasm-exceptions and -sSUPPORT_LONGJMP=wasm for the Emscripten
toolchain. This implements setjmp/longjmp using native WebAssembly
exception handling instructions instead of Asyncify-based emulation.
Benefits:
- Minimal memory overhead (no shadow stack buffer needed)
- No code size penalty
- Works with both C and C++ code
WASM exception handling is supported by all major browsers since 2021-2022
(Chrome 95+, Firefox 100+, Safari 15.2+) and standalone runtimes
(Node.js 17+, Wasmtime, Wasmer).
For older runtimes, users can override with CFLAGS/LDFLAGS environment
variables.
Co-authored-by: Claude <noreply@anthropic.com>
Yukihiro "Matz" Matsumoto