support asmjs-unknown-emscripten and wasm32-unknown-emscripten

[japaric]

cc @brson

cross build --target asmjs-unknown-emscripten and node hello.js works.

cross test --target asmjs-unknown-emscripten (and cross run) would Just Work if rustc generated executable .js files with a #!/usr/bin/env node shebang in it.

cross build --target wasm-unknown-emscripten succeeds but its output fails to run using node:

$ node target/wasm32-unknown-emscripten/release/hello.js
trying binaryen method: native-wasm
no native wasm support detected

/home/japaric/tmp/hello/target/wasm32-unknown-emscripten/release/hello.js:462
      throw ex;
      ^
no binaryen method succeeded. consider enabling more options, like interpreting, if you want that: https://github.com/kripken/emscripten/wiki/WebAssembly#binaryen-methods

Is this a regression? @brson reported that node hello.wasm.js worked way back in this thread.

[japaric]

@homunkulus try

[homunkulus]

⌛ Trying commit 4de2d6e with merge 4de2d6e...

[japaric]

The job exceeded the maximum time limit for jobs, and has been terminated.

😢

[homunkulus]

💔 Test failed - status-travis

[homunkulus]

☔ The latest upstream changes (presumably 5d70947) made this pull request unmergeable. Please resolve the merge conflicts.

[japaric]

cross build --target wasm-unknown-emscripten succeeds but its output fails to run using node:

I figured out how to run this output using node. You need to build node from this branch and pass the --expose-wasm flag to node (hat tip to @chicoxyzzy):

$ node --expose-wasm hello-fbbdd13f43d45d24.js
trying binaryen method: native-wasm
binaryen method succeeded.
Hello, world!

The weird part is that it expects the .wasm file that Cargo also outputs to be in the same directory as the .js file ... so this doesn't work:

$ ls target/wasm32-unknown-emscripten/release/
build  deps  examples  hello.js  native

$ node --expose-wasm target/wasm32-unknown-emscripten/release/hello.js
trying binaryen method: native-wasm
failed to compile wasm module: Error: ENOENT: no such file or directory, open 'hello-fbbdd13f43d45d24.wasm'

/mnt/hello/target/wasm32-unknown-emscripten/release/hello.js:462
      throw ex;
      ^
no binaryen method succeeded. consider enabling more options, like interpreting, if you want that: https://github.com/kripken/emscripten/wiki/WebAssembly#binaryen-methods

Nor this:

$ ls target/wasm32-unknown-emscripten/release/deps/
hello-fbbdd13f43d45d24.asm.js  hello-fbbdd13f43d45d24.wasm
hello-fbbdd13f43d45d24.js      hello-fbbdd13f43d45d24.wast

$ node --expose-wasm target/wasm32-unknown-emscripten/release/deps/hello-fbbdd1
3f43d45d24.js
trying binaryen method: native-wasm
failed to compile wasm module: Error: ENOENT: no such file or directory, open 'hello-fbbdd13f43d45d24.wasm'

/mnt/hello/target/wasm32-unknown-emscripten/release/deps/hello-fbbdd13f43d45d24.js:462
      throw ex;
      ^
no binaryen method succeeded. consider enabling more options, like interpreting, if you want that: https://github.com/kripken/emscripten/wiki/WebAssembly#binaryen-methods

It has to be executed like this:

$ cd target/wasm32-unknown-emscripten/release/deps

$ node --expose-wasm hello-fbbdd13f43d45d24.js
trying binaryen method: native-wasm
binaryen method succeeded.
Hello, world!

Which pretty much precludes cargo run and cargo test from working with this target.

[chicoxyzzy]

Hi Jorge!

I haven't tried using cross yet but I think I can provide some information that might (or might not) be useful for it as well. Looks like currently it's not possible to use -o option with file target using cargo. Without -o option it's impossible to compile to HTML.

$ cargo rustc --target=wasm32-unknown-emscripten -- -o wasm.html
   Compiling wasm-test3 v0.1.0 (file:///Users/Chico/Projects/wasm-test3)
warning: ignoring specified output filename because multiple outputs were requested

warning: ignoring --out-dir flag due to -o flag.

Although it's more like emcc issue I think

[japaric]

@chicoxyzzy Hmm, if emcc provides another way to make it output html, you could use cargo rustc --target wasm32-unknown-emscripten -- -C link-arg=$flag-for-emcc.

[japaric]

rebased. This will likely not land because of timeouts but let's try anyway.

@homunkulus r+

[japaric]

@homunkulus r+

[homunkulus]

📌 Commit 9491053 has been approved by japaric

[homunkulus]

⌛ Testing commit 9491053 with merge 9491053...

[homunkulus]

📌 Commit a866006 has been approved by japaric

[homunkulus]

💥 Test timed out

[homunkulus]

☔ The latest upstream changes (presumably #81) made this pull request unmergeable. Please resolve the merge conflicts.

[jan-hudec]

Since rust-lang/cargo#3954 got merged, setting

[target.asmjs-unknown-emscripten]
linker = "emcc"
runner = "node"

makes cargo test --target asmjs-unknown-emscripten work.

Per comments above, with the right version of node, the following should make cargo test --target wasm32-unknown-emscripten work too:

[target.wasm32-unknown-emscripten]
linker = "emcc"
runner = "node --expose-wasm"

[japaric]

Closing in favor of #106