Clearer linker error due to sjlj ABI mismatch?

[hoodmane]

Source file:

#include <setjmp.h>

jmp_buf buf;

int main() {
    longjmp(buf, 8);
}

Compile/link:

$ emcc -c a.c
$ emcc a.o -fwasm-exceptions
error: undefined symbol: emscripten_longjmp (referenced by root reference (e.g. compiled C/C++ code

Would be nice if the error could say something roughly like:

a.o uses setjmp/longjmp but was compiled with incompatible ABI. Pass -fwasm-exceptions as a compile flag.

[anutosh491]

Thanks for the report. Can try looking into this soon !

[sbc100]

I created an llvm-side fix that (llvm/llvm-project#128564) as well as an emscripten-side fix that should help make this more clear #23738.

[hoodmane]

Thanks for the quick fix @sbc100!