emscripten: add pthread_sigmask, sigwait, faccessat, pthread_kill, se… by guybedford · Pull Request #5270 · rust-lang/libc

guybedford · 2026-07-10T01:40:27Z

Adds remaining gated wasm32-unknown-emscripten APIs which are implemented by Emscripten - pthread_sigmask, sigwait, sigwaitinfo, faccessat, pthread_kill.

Link: https://github.com/emscripten-core/emscripten/blob/6a93f7db16cd8e5214b4c3c08a361ccab9ffc67e/system/lib/libc/musl/include/signal.h#L225-L227
Link: https://github.com/emscripten-core/emscripten/blob/6a93f7db16cd8e5214b4c3c08a361ccab9ffc67e/system/lib/libc/musl/include/signal.h#L230-L231
Link: https://github.com/emscripten-core/emscripten/blob/6a93f7db16cd8e5214b4c3c08a361ccab9ffc67e/system/lib/libc/musl/include/unistd.h#L88

tgross35

Thanks!

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…faccessat, pthread_kill Link: https://github.com/emscripten-core/emscripten/blob/6a93f7db16cd8e5214b4c3c08a361ccab9ffc67e/system/lib/libc/musl/include/signal.h#L225-L227 Link: https://github.com/emscripten-core/emscripten/blob/6a93f7db16cd8e5214b4c3c08a361ccab9ffc67e/system/lib/libc/musl/include/signal.h#L230-L231 Link: https://github.com/emscripten-core/emscripten/blob/6a93f7db16cd8e5214b4c3c08a361ccab9ffc67e/system/lib/libc/musl/include/unistd.h#L88

rustbot · 2026-07-10T19:47:26Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

Adds wasm32-unknown-emscripten as a target for nix, plus a CI job that runs the full test suite under Node. Source changes to compile on emscripten (which behaves like a Linux/musl libc): * ioctl: use the Linux ioctl module and a c_int ioctl_num_type on emscripten (src/sys/ioctl, src/sys/mod.rs). * resource: enable getrlimit/setrlimit and the Resource enum via libc::rlimit. * socket: include emscripten in the SockaddrStorage AF_UNIX (pathname/unnamed) decode arms. * unistd: sethostname is unavailable on emscripten, so gate it out. The suite spawns OS threads (signal and socket-peer tests), so std is rebuilt with atomics via -Zbuild-std and linked -pthread with -sPROXY_TO_PTHREAD so the main thread can block; JSPI (-sJSPI) provides the return-to-host suspension for blocking reads/writes, and NODERAWFS/NODERAWSOCKETS back the filesystem and sockets with node's. This needs nightly + rust-src and a JSPI-capable Node (26+, or 22 with --experimental-wasm-jspi). No custom target spec is required: nightly now emits the __main_argc_argv entry point (rust-lang/rust#158937). Genuinely-unsupported operations are ignored with #[cfg_attr(target_os = "emscripten", ignore)] rather than cfg'd out, covering fork/wait, pty/termios, mkfifo, getpwnam/setgroups/acct, flock, if_nametoindex, pipe2 FD_CLOEXEC, AF_UNIX SCM_RIGHTS/datagram, thread signal masking, and setrlimit; a few tests are cfg'd out where the feature is entirely absent (raw signal actions, socketpair) or the host differs (linkat symlink follow). Temporary, until the dependencies land upstream: * Cargo.toml patches libc to guybedford/libc#libc-0.2-emscripten for the emscripten externs (rust-lang/libc#5270). * the CI job builds against the guybedford/emscripten `cf` fork, which carries the NODEFS/socket/blocking patches this target depends on (emscripten-core/emscripten#27305, #27306). Suite result: 148 passed, 0 failed, 35 ignored under Node - green on Linux CI.

Adds wasm32-unknown-emscripten as a target for nix, plus a CI job that runs the full test suite under Node. Source changes to compile on emscripten (which behaves like a Linux/musl libc): * ioctl: use the Linux ioctl module and a c_int ioctl_num_type on emscripten (src/sys/ioctl, src/sys/mod.rs). * resource: enable getrlimit/setrlimit and the Resource enum via libc::rlimit. * socket: include emscripten in the SockaddrStorage AF_UNIX (pathname/unnamed) decode arms. * unistd: sethostname is unavailable on emscripten, so gate it out. The suite spawns OS threads (signal and socket-peer tests), so std is rebuilt with atomics via -Zbuild-std and linked -pthread with -sPROXY_TO_PTHREAD so the main thread can block; JSPI (-sJSPI) provides the return-to-host suspension for blocking reads/writes, and NODERAWFS/NODERAWSOCKETS back the filesystem and sockets with node's. This needs nightly + rust-src and a JSPI-capable Node (26+, or 22 with --experimental-wasm-jspi). No custom target spec is required: nightly now emits the __main_argc_argv entry point (rust-lang/rust#158937). Genuinely-unsupported operations are ignored with fork/wait, pty/termios, mkfifo, getpwnam/setgroups/acct, flock, if_nametoindex, pipe2 FD_CLOEXEC, AF_UNIX SCM_RIGHTS/datagram, thread signal masking, and setrlimit; a few tests are cfg'd out where the feature is entirely absent (raw signal actions, socketpair) or the host differs (linkat symlink follow). Temporary, until the dependencies land upstream: * Cargo.toml patches libc to guybedford/libc#libc-0.2-emscripten for the emscripten externs (rust-lang/libc#5270). * the CI job builds against the guybedford/emscripten `cf` fork, which carries the NODEFS/socket/blocking patches this target depends on (emscripten-core/emscripten#27305, #27306). Suite result: 148 passed, 0 failed, 35 ignored under Node - green on Linux CI.

Adds wasm32-unknown-emscripten as a target for nix, plus a CI job that runs the full test suite under Node. Source changes to compile on emscripten (which behaves like a Linux/musl libc): * ioctl: use the Linux ioctl module and a c_int ioctl_num_type on emscripten (src/sys/ioctl, src/sys/mod.rs). * resource: enable getrlimit/setrlimit and the Resource enum via libc::rlimit. * socket: include emscripten in the SockaddrStorage AF_UNIX (pathname/unnamed) decode arms. * unistd: sethostname is unavailable on emscripten, so gate it out. The suite spawns OS threads (signal and socket-peer tests), so std is rebuilt with atomics via -Zbuild-std and linked -pthread with -sPROXY_TO_PTHREAD so the main thread can block; JSPI (-sJSPI) provides the return-to-host suspension for blocking reads/writes, and NODERAWFS/NODERAWSOCKETS back the filesystem and sockets with node's. This needs nightly + rust-src and a JSPI-capable Node (26+, or 22 with --experimental-wasm-jspi). No custom target spec is required: nightly now emits the __main_argc_argv entry point (rust-lang/rust#158937). Unsupported operations are ignored with #[cfg_attr(target_os = "emscripten", ignore)] rather than cfg'd out wherever they still compile, covering fork/wait, pty/termios, mkfifo, getpwnam/setgroups/acct, flock, if_nametoindex, pipe2 FD_CLOEXEC, AF_UNIX SCM_RIGHTS/datagram, getsockname, socketpair, setrlimit, and the linkat symlink-follow host check. The signal-delivery tests (signal, killpg, thread mask) and the AF_ROUTE test are cfg'd out instead: compiling their extern "C" handlers in perturbs the wasm indirect function table and aborts the runtime. Temporary, until the dependencies land upstream: * the emscripten CI job injects a libc patch (guybedford/libc#libc-0.2-emscripten, rust-lang/libc#5270) via `cargo --config`, so other targets and CI jobs are unaffected. * it also builds against the guybedford/emscripten `cf` fork, which carries the NODEFS/socket/blocking patches this target depends on (emscripten-core/emscripten#27305, #27306). Suite result: 148 passed, 0 failed, 38 ignored under Node - green on Linux CI.

Adds `wasm32-unknown-emscripten` as a target for mio, plus a CI job that runs the suite under Node. Resolves tokio-rs#642. Emscripten exposes a real epoll backed by its runtime event loop, so the existing Linux epoll selector is reused rather than adding a new backend. The wasm `compile_error!` guard is relaxed to let emscripten through, and the `epoll`/`eventfd`/pipe-waker cfg lists gain emscripten. Because emscripten cannot block in `epoll_wait` without JSPI/ASYNCIFY, two non-blocking readiness paths are added alongside the normal `Poll::poll`: * `Poll::new_with_callback` arms a persistent callback on the epoll fd via the runtime's `emscripten_epoll_set_callback`, delivering ready events on a fresh host tick whenever the set makes progress. The callback state is boxed, owned by the arming selector, and disarmed on drop; it may freely re-enter mio to (de)register sources. * `Registry::poll_ready` does a zero-timeout drain of the same epoll set as a readiness probe where a blocking wait is impossible. AF_UNIX support is stream-only: emscripten's node-backed sockets have no datagram primitive, so `UnixDatagram` and the `socketpair`-based helpers are not compiled there. Sockets set `O_NONBLOCK` via `fcntl` since emscripten's `socket(2)` silently strips `SOCK_NONBLOCK`/`SOCK_CLOEXEC`. The suite spawns OS threads (socket-peer test harnesses), so std is rebuilt with atomics via -Zbuild-std and linked -pthread with -sPROXY_TO_PTHREAD so the main thread can block; JSPI (-sJSPI) provides the return-to-host suspension for blocking reads/writes, and NODERAWFS/NODERAWSOCKETS back the filesystem and sockets with node's. This needs nightly + rust-src and a JSPI-capable Node (26+, or 22 with --experimental-wasm-jspi). No custom target spec is required: nightly now emits the __main_argc_argv entry point (rust-lang/rust#158937). Doctests are skipped on this target: rustdoc does not apply the emcc link args, so the examples cannot be linked with the socket/thread runtime. Temporary, until the dependencies land upstream: * Cargo.toml patches libc to guybedford/libc#emscripten for the emscripten epoll/pthread externs (rust-lang/libc#5270). * the CI job builds against the guybedford/emscripten `cf` fork, which carries the epoll callback (emscripten-core/emscripten#27207), AF_UNIX pathname stream sockets, and multicast getsockopt patches this target depends on. Suite result: 148 passed, 0 failed, 3 ignored under Node - green on CI.

Adds `wasm32-unknown-emscripten` as a target for mio, plus a CI job that runs the suite under Node. Resolves tokio-rs#642. Emscripten exposes a real epoll backed by its runtime event loop, so the existing Linux epoll selector is reused rather than adding a new backend. The wasm `compile_error!` guard is relaxed to let emscripten through, and the `epoll`/`eventfd`/pipe-waker cfg lists gain emscripten. Because emscripten cannot block in `epoll_wait` without JSPI/ASYNCIFY, the epoll fd is exposed via `AsRawFd` on `Poll`/`Registry` so the runtime driving mio can arm emscripten's `emscripten_epoll_set_callback` on it directly, delivering ready events on a fresh host tick whenever the set makes progress. A zero-timeout `Poll::poll` remains available as a synchronous readiness probe where a blocking wait is impossible. AF_UNIX support is stream-only: emscripten's node-backed sockets have no datagram primitive, so `UnixDatagram` and the `socketpair`-based helpers are not compiled there. Sockets set `O_NONBLOCK` via `fcntl` since emscripten's `socket(2)` silently strips `SOCK_NONBLOCK`/`SOCK_CLOEXEC`. The suite spawns OS threads (socket-peer test harnesses), so std is rebuilt with atomics via -Zbuild-std and linked -pthread with -sPROXY_TO_PTHREAD so the main thread can block; JSPI (-sJSPI) provides the return-to-host suspension for blocking reads/writes, and NODERAWFS/NODERAWSOCKETS back the filesystem and sockets with node's. This needs nightly + rust-src and a JSPI-capable Node (26+, or 22 with --experimental-wasm-jspi). No custom target spec is required: nightly now emits the __main_argc_argv entry point (rust-lang/rust#158937). Doctests are skipped on this target: rustdoc does not apply the emcc link args, so the examples cannot be linked with the socket/thread runtime. Temporary, until the dependencies land upstream: * Cargo.toml patches libc to guybedford/libc#emscripten for the emscripten epoll/pthread externs (rust-lang/libc#5270). * the CI job builds against the guybedford/emscripten `cf` fork, which carries AF_UNIX pathname stream sockets and multicast getsockopt patches this target depends on. Suite result: 146 passed, 0 failed, 3 ignored under Node - green on CI.

Adds `wasm32-unknown-emscripten` as a target for mio, plus a CI job that runs the suite under Node. Resolves tokio-rs#642. Emscripten exposes a real epoll backed by its runtime event loop, so the existing Linux epoll selector is reused rather than adding a new backend. The wasm `compile_error!` guard is relaxed to let emscripten through, and the `epoll`/`eventfd`/pipe-waker cfg lists gain emscripten. Because emscripten cannot block in `epoll_wait` without JSPI/ASYNCIFY, the epoll fd is exposed via `AsRawFd` on `Poll`/`Registry` so the runtime driving mio can arm emscripten's `emscripten_epoll_set_callback` on it directly, delivering ready events on a fresh host tick whenever the set makes progress. A zero-timeout `Poll::poll` remains available as a synchronous readiness probe where a blocking wait is impossible. AF_UNIX support is stream-only: emscripten's node-backed sockets have no datagram primitive, so `UnixDatagram` and the `socketpair`-based helpers are not compiled there. Sockets set `O_NONBLOCK` via `fcntl` since emscripten's `socket(2)` silently strips `SOCK_NONBLOCK`/`SOCK_CLOEXEC`. The suite spawns OS threads (socket-peer test harnesses), so std is rebuilt with atomics via -Zbuild-std and linked -pthread with -sPROXY_TO_PTHREAD so the main thread can block; JSPI (-sJSPI) provides the return-to-host suspension for blocking reads/writes, and NODERAWFS/NODERAWSOCKETS back the filesystem and sockets with node's. This needs nightly + rust-src and a JSPI-capable Node (26+, or 22 with --experimental-wasm-jspi). No custom target spec is required: nightly now emits the __main_argc_argv entry point (rust-lang/rust#158937). Doctests are skipped on this target: rustdoc does not apply the emcc link args, so the examples cannot be linked with the socket/thread runtime. Temporary, until the dependencies land upstream: * Cargo.toml patches libc to guybedford/libc#emscripten for the emscripten epoll/pthread externs (rust-lang/libc#5270). * the CI job builds against the guybedford/emscripten `cf` fork, which carries AF_UNIX pathname stream sockets and multicast getsockopt patches this target depends on. The two `reconnect_udp_socket_*` tests are ignored on emscripten: libuv does not re-associate a connected UDP socket when it is reconnected to a new peer, so no readiness is delivered for the new peer. Suite result: 144 passed, 0 failed, 5 ignored under Node - green on CI.

Adds `wasm32-unknown-emscripten` as a target for mio, plus a CI job that runs the suite under Node. Resolves tokio-rs#642. Emscripten exposes a real epoll backed by its runtime event loop, so the existing Linux epoll selector is reused rather than adding a new backend. The wasm `compile_error!` guard is relaxed to let emscripten through, and the `epoll`/`eventfd`/pipe-waker cfg lists gain emscripten. Because emscripten cannot block in `epoll_wait` without JSPI/ASYNCIFY, the epoll fd is exposed via `AsRawFd` on `Poll`/`Registry` so the runtime driving mio can arm emscripten's `emscripten_epoll_set_callback` on it directly, signalling on a fresh host tick whenever the set has ready events. A zero-timeout `Poll::poll` remains available as a synchronous readiness probe where a blocking wait is impossible. AF_UNIX support is stream-only: emscripten's node-backed sockets have no datagram primitive, so `UnixDatagram` and the `socketpair`-based helpers are not compiled there. Sockets set `O_NONBLOCK` via `fcntl` since emscripten's `socket(2)` silently strips `SOCK_NONBLOCK`/`SOCK_CLOEXEC`. The suite spawns OS threads (socket-peer test harnesses), so std is rebuilt with atomics via -Zbuild-std and linked -pthread with -sPROXY_TO_PTHREAD. Blocking harness socket ops (accept/recv) block their pthread through emscripten's sync-proxy wait primitive (`_emscripten_fd_wait`) - no JSPI or stack suspension is involved anywhere in the suite. NODERAWFS/NODERAWSOCKETS back the filesystem and sockets with node's. This needs nightly + rust-src. No custom target spec is required: nightly now emits the __main_argc_argv entry point (rust-lang/rust#158937). Doctests are skipped on this target: rustdoc does not apply the emcc link args, so the examples cannot be linked with the socket/thread runtime. Temporary, until the dependencies land upstream: * Cargo.toml patches libc to guybedford/libc#emscripten for the emscripten epoll/pthread externs (rust-lang/libc#5270). * the CI job builds against the guybedford/emscripten `cf` fork, which carries the epoll callback, `_emscripten_fd_wait` blocking-ops, AF_UNIX pathname stream socket, and multicast getsockopt patches this target depends on. The two `reconnect_udp_socket_*` tests are ignored on emscripten: libuv does not re-associate a connected UDP socket when it is reconnected to a new peer, so no readiness is delivered for the new peer. Suite result: 144 passed, 0 failed, 5 ignored under Node - green on CI.

rustbot added the S-waiting-on-review label Jul 10, 2026

guybedford force-pushed the emscripten-apis branch from c210229 to ce12efb Compare July 10, 2026 01:42

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tgross35 added the stable-nominated This PR should be considered for cherry-pick to libc's stable release branch label Jul 10, 2026

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guybedford mentioned this pull request Jul 11, 2026

Add wasm32-unknown-emscripten target support nix-rust/nix#2805

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Add wasm32-unknown-emscripten target support tokio-rs/mio#1969

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