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Do you have an example of getting bazel to work with emscripten? I’ll share mine if you share yours: https://github.com/sorbet/sorbet/tree/master/tools/toolch

by jez 6y ago

Do you have an example of getting bazel to work with emscripten? I’ll share mine if you share yours: https://github.com/sorbet/sorbet/tree/master/tools/toolchain/webasm-linux https://github.com/sorbet/sorbet/tree/master/tools/toolchain... When we set this up to compile Sorbet (C++ codebase) for https://sorbet.run https://sorbet.run, it involved what I considered an inordinate amount of boilerplate and arcana. To be fair since we set it up it’s hardly ever needed to be touched, and I could probably cargo cult this into future projects where I wanted to use it, but I wouldn’t exactly say that bazel magically makes the pain of emscripten go away. Curious to hear otherwise.

haberman 6y ago
Yikes. That definitely seems more complicated than it should be. I have not used Emscripten in this way before, I was going from my experience of passing custom flags like -fsanitize=address. I was under the impression that Emscripten was just an alternative compiler binary, such that you could just use CC=emcc. Is that not the case?
- jez 6y ago
  The trick is that to provide Bazel with a custom toolchain involves way more than just setting an environment variable, because Bazel wants to control installing and making available the compiler reliably (e.g., what if `emcc` is not present on the system where Bazel was invoked? Bazel solves that problem by fetching it and building it for that system) There are projects that provide drop-in support for custom toolchains (e.g., we use this project[0] in Sorbet to fetch and build a custom LLVM/Clang toolchain for every host we build on (rather than relying on the system toolchain). But I'm not aware of a project that has done that for Emscripten. Maybe it would be as easy as plucking out what we've done in our project into a project that others could depend on, but to quote a colleague: > Setting up a cc toolchain in Bazel is a unique sort of pain. [0] https://github.com/grailbio/bazel-toolchain/ https://github.com/grailbio/bazel-toolchain/

by jez 6y ago

haberman 6y ago

Yikes. That definitely seems more complicated than it should be. I have not used Emscripten in this way before, I was going from my experience of passing custom flags like -fsanitize=address. I was under the impression that Emscripten was just an alternative compiler binary, such that you could just use CC=emcc. Is that not the case?

jez 6y ago
The trick is that to provide Bazel with a custom toolchain involves way more than just setting an environment variable, because Bazel wants to control installing and making available the compiler reliably (e.g., what if `emcc` is not present on the system where Bazel was invoked? Bazel solves that problem by fetching it and building it for that system) There are projects that provide drop-in support for custom toolchains (e.g., we use this project[0] in Sorbet to fetch and build a custom LLVM/Clang toolchain for every host we build on (rather than relying on the system toolchain). But I'm not aware of a project that has done that for Emscripten. Maybe it would be as easy as plucking out what we've done in our project into a project that others could depend on, but to quote a colleague: > Setting up a cc toolchain in Bazel is a unique sort of pain. [0] https://github.com/grailbio/bazel-toolchain/ https://github.com/grailbio/bazel-toolchain/