emcc can't find wasm-ld

[Osman Zakir]

Just now I tried to run em++ after setting EMCC_WASM_BACKEND and EMCC_DEBUG variables to 1 and I got this error:

shared:ERROR: WASM_BACKEND selected but could not find lld (wasm-ld): C:/Users/Osman/emsdk/clang/e1.38.20_64bit\wasm-ld.exe

I'd ran these commands before that:

emsdk install latest --vs2017 --build=Release
emsdk activate latest --vs2017 --build=Release
emsdk_env

I'd really like some help here.  Thanks in advance.

[Floh]

Just FYI (no solution unfortunately) I also ran into problem when trying to use the LLVM backend, my order of trial-and-error steps was roughly (from memory):

- .emscripten file needs path to binaryen (BINARYEN_ROOT), so I pulled and built binaryen from github, and added the line the .emscripten

- the next error message was a note to install emscripten (via emsdk) with the '--enable-wasm' flag, so I did that (hoping that this would produce the requested wasm-ld executable)

- ...but no luck, the wasm-ld executable isn't found (it's there no wasm-* executables at all at the path where emscripten is looking for)

This was on macOS and with the emscripten incoming branch (and binaryen master).

That's where I gave up :) I'd be interested in testing the llvm backend with my code too, so some help or pointers into the right direction would be welcome.

-Floh.

[Alon Zakai]

Emscripten's github CI now tests the LLVM backend, so you may be able to do something similar to what we do there,

https://github.com/kripken/emscripten/blob/incoming/.circleci/config.yml#L330

The key part there is

./emsdk --notty install clang-upstream-NUM

where NUM needs to be found out first. We should probably simplify that - this is all pretty new and in progress.

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[Floh]

Hmm, I followed those CI scripts step by step but it failed on Mac because emsdk complains that clang-upstream-12345 doesn't exist or something (don't remember what the exact build-number was, it's the one extracted from the lkgr.json file).

I'm trying my luck now with building my own llvm toolchain via the scripts in here:

https://github.com/tpimh/wasm-toolchain

It's not high-priority for me though, just playing around and I wanted to check whether my emulators work at all and what's the performance difference is :)

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[Floh]

Heh, interesting: when building the LLVM toolchain myself, with:

cmake -G Ninja -DCMAKE_INSTALL_PREFIX=../llvm-wasm -DLLVM_TARGETS_TO_BUILD= -DLLVM_TARGET_ARCH=wasm32 -DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=WebAssembly ../llvm

...and then trying to compile a simple .c file with:

llvm-wasm/bin/clang example/sample.c -o sample.wasm --target=wasm32 -nostdlib -Xlinker --no-entry -Xlinker --allow-undefined

I'm getting *exactly* the same error message as the OP:

clang-8: error: unable to execute command: Executable "wasm-ld" doesn't exist!

clang-8: error: lld command failed with exit code 1 (use -v to see invocation)

...because lld/wasm-lld doesn't seem included in a normal LLVM build.

I'm currently trying to figure out how to build wasm-ldd... (it seems to be different from building other optional

LLVM components, like the clang frontend).

[Alon Zakai]

Hmm, yeah, I'm not sure if the waterfall builders have anything other than linux yet. Using it this way is pretty new.

You can grab lld from source and build it, i do that locally, then I add a symlink to the llvm bin dir so tools find it.

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