Add support for non-windows/unix targets

[dflemstr]

This is mostly for wasm support and I'm not sure if this approach is great for other targets.

I could also add a continuous integration job for this target if necessary.

[carllerche]

Thanks.

Could you provide more context about how this would be used on wasm? Also, a CI branch would be appreciated.

I also think this is based on the 0.1.x branch. I switched master to represent 0.2.x. This can be handled in a separate PR though.

[dflemstr]

@carllerche There is no iovec concept in wasm AFAIK since that is a UNIX (POSIX?) specific concept. Since the heap isn't segmented I don't see an advantage in tracking iovec memory at all on that architecture, since I can't think of anything reasonable a readv(2) implementation could use it for.

This PR is of course a bit generic since it assumes no iovec support by default on unknown platforms. Maybe it's better to cause a compilation error and whitelist specific architectures?

[dflemstr]

Not sure why the build is failing; it builds locally...

[carllerche]

Is there a way to run wasm targets in CI?

I guess at the very least, CI compiles but doesn't run?

[dflemstr]

@carllerche it's possible to run them using a significant amount of node.js scaffolding. What would you like to do? Create a program that exercises this code path?

[koute]

Is there a way to run wasm targets in CI?

At least on Travis you can run all of the Rust's web targets pretty easily with cargo-web if that's what you want; for example:

# Install nodejs
nvm install 9

# Unfortunately we don't have binary packages for cargo-web yet
cargo install cargo-web

rustup target add asmjs-unknown-emscripten
cargo web test --nodejs --target-asmjs-emscripten

rustup target add wasm32-unknown-emscripten
cargo web test --nodejs --target-webasm-emscripten

set +e
echo "$(rustc --version)" | grep -q "nightly"
if [ "$?" = "0" ]; then
    export IS_NIGHTLY=1
else
    export IS_NIGHTLY=0
fi
set -e

if [ "$IS_NIGHTLY" = "1" ]; then
    rustup target add wasm32-unknown-unknown
    cargo web test --nodejs --target-webasm
fi

That will run the tests for all three web targets using nodejs. Running the tests in a headless chromium is also supported for the *-emscripten targets (if you don't pass the --nodejs flag), but you wouldn't really need that.

Just please note that right now a lot of stuff on the wasm32-unknown-unknown target (like, for example, println! calls) do nothing, so if the tests on that target fail you won't know what went wrong. Once rust-lang/rust#47102 lands I'll add support for it in cargo-web so that println! and such will work.

[carllerche]

Interesting. I'm less interested in getting full test parity, mostly ensure things "work" at some level.

[carllerche]

Ok, I think this is good now. Thanks!