Cannot build on wasm32-unknown-unknown target about rust-onig HOT 8 CLOSED

Got this error when wanting to use onig with wasm32-unknown-unknown. Then I remembered when I was working with emscripten once, that Rust doesn't really allow you to compile C libraries unless it's with emscripten. Except the emscripten target is not maintained well..

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Last I knew, building C libraries is only possible with emscripten unfortunately.

Edit: rustwasm/team#291 and rustwasm/team#291 (comment)

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I’ve never built Onig for WASM. The Artichoke peeps have though. This is their reference: https://github.com/artichoke/artichoke/blob/414b7a2fe387c480d1385efb0f63963153754a3e/artichoke-backend/Cargo.toml#L31

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I wonder if the default features could be the difference. Disabling that will mean we don’t try to generate an up to date set of bindings and fall back on our built in set. I guess we have one that works for WASM if Artichoke has it working.

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I guess we have one that works for WASM if Artichoke has it working.

Artichoke does not build with wasm32-unknown-unknown -- it builds with wasm32-unknown-emscripten. In general, when building C sources as part of a Rust lib or binary, the wasm32-unknown-unknown will not work. There is no C standard library in wasm32-unknown-unknown.

This upstream issue is relevant for one reason why this doesn't work: rustwasm/team#291.

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The Artichoke peeps have though.

@iwillspeak next time, please feel free to @ me if there's onig-Artichoke questions I can help with 😄

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On Ubtuntu 18.04, using "wasm-pack", I had got the same fatal error: 'stdlib.h' file not found problem, mentioned in the original issue description.
I have solved it by

export CPATH=/usr/include

However, now I get the error message

 rust-lld: error: duplicate symbol: OnigEncodingASCII
          >>> defined in /home/marco/workspace/private/wasm-game-of-life-2/target/wasm32-unknown-unknown/debug/deps/libonig_sys-538ff2b6c9a16eb8.rlib(regexec.o)
          >>> defined in /home/marco/workspace/private/wasm-game-of-life-2/target/wasm32-unknown-unknown/debug/deps/libonig_sys-538ff2b6c9a16eb8.rlib(regerror.o)

Is this the kind of error that will vanish when I somehow configure wasm-pack to create a wasm32-unknown-emscripten target output?
Have you seen this error before?

(I have now solved my original problem by using a different regexp crate, but maybe this comment is somehow helpful, so I leave it here).

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Doing some more digging on this, it seems that the underlying c library, Oniguruma, doesn't build cleanly on either wasm32-unknown-unknown, or wasm32-unknown-emscripten. Not sure what we can do better about this from an Onig point of view. If anyone has more experience with these toolchains and wants to open a PR with suggested improvements it would be more than welcome.

EDIT Scratch that. Onig does build on Emscripten if you have the rust target wasm32-unknown-emscripten installed and use

cargo build --no-default-features --target=wasm32-unknown-emscripten --features=generate

I'm not really sure what we can do about building for -unknown-unknown though. The build fails there because it can't find c libraries:

running: "clang" "-O0" "-ffunction-sections" "-fdata-sections" "-fPIC" "-g" "-fno-omit-frame-pointer" "--target=wasm32-unknown-unknown" "-I" "/home/will/Repositories/rust-onig/target/wasm32-unknown-unknown/debug/build/onig_sys-d79b79668a7ad64f/out" "-I" "oniguruma/src" "-DONIG_DISABLE_DIRECT_THREADING=1" "-DONIG_EXTERN=__attribute__((visibility(\"default\")))" "-o" "/home/will/Repositories/rust-onig/target/wasm32-unknown-unknown/debug/build/onig_sys-d79b79668a7ad64f/out/oniguruma/src/regexec.o" "-c" "oniguruma/src/regexec.c"
  cargo:warning=In file included from oniguruma/src/regexec.c:36:
  cargo:warning=oniguruma/src/regint.h:109:10: fatal error: 'stdlib.h' file not found
  cargo:warning=#include <stdlib.h>
  cargo:warning=         ^~~~~~~~~~
  cargo:warning=1 error generated.

Still open to any PRs if people want to contribute, but closing this issue for now.

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