wasm-eh: wasm-ld error in relocation R_WASM_MEMORY_ADDR_SLEB cannot be used against symbol GCC_except_table0

[sps-gold]

wasm-ld throws relocation error building with wasm-exceptions, for c++ catch without ellipse and using mainmodule flag

here is a small reproducer #15170 for the error we are seeing during building some of our tests

wasm-ld: error: lto.tmp: relocation R_WASM_MEMORY_ADDR_SLEB cannot be used against symbol GCC_except_table0; recompile with -fPIC

following is the link to ci error

[kripken]

@aheejin is this a known issue? Not sure it's specific to exceptions though, maybe it's more of a relocation linking issue...

[aheejin]

Yes, this is a known issue, and I'm working on the fix. Likely to be fixed within a few days.

[sps-gold]

@aheejin I was trying if I could cherry pick your changes to test with emsdk 2.0.26. So far I had just tried building llvm binaries but that wasnt enough. I also find more changes coming in. So at this point can I check with you, if you think your changes are kind of done and if they are independent enough that I would be able to cherrypick and try.

[aheejin]

Sorry for the long delay, and the fix is in #15266 (and its companion patches). I'm not sure how you cherry-picked my patch, given that any of the patches (LLVM, Binaryen, and Emscripten) hasn't landed. Do you mean you downloaded each of the three patches and applied them and compiled LLVM and Binaryen yourself?

I think you at least need to wait until these patches land, and you can either use emsdk install latest to pick up the latest trunk, or wait until the next release. I'm not sure what you exactly mean by cherry-picking.

[sps-gold]

yes, that's right I took your changes and build the binaries myself.

Thanks @aheejin for fixing the issue, this really helps us unblock ourself from further validation of the upcoming eh feature.
I see I can now build and run the reproducer successfully, so now I can continue to build main app and uncover other issues if any.

~/Source/github/sps-gold/test$ ./runtime/d8_ver9.5/d8 --experimental-wasm-eh ./test_exceptions_std.js
what? std::exception
caught std::exception

[aheejin]

Oh, that must have been a hassle to download all patches and build them yourself. Sorry for the inconvenience. Do you mean applying the patches fixed your issue?

But anyway I recommend switching back to our vanilla release after these patches land and are included in the next release. Also these three patches may change according to pending code review. (The current version works, but reviewers may suggest a better structure or something)

[sps-gold]

Well it was rather a great learning :) .
Yes that's right after applying your patch I could build successfully and could run the reproducer with d8 9.5 (latest available node 16.11.0 do not seem to have support yet).

I do understand that your changes are not final, and we only use release builds for production.
PS: Attaching the output for reference
output.zip