emscripten: Add epoll support

Emscripten restored the `sys/epoll.h` header in 6.0.2 and implements
`epoll_create`, `epoll_create1`, `epoll_ctl`, `epoll_wait` and
`epoll_pwait` in the JS filesystem as of 6.0.8.

Version detection in libc-test now also tracks the tiny version
component so that point releases can be distinguished, and parses the
uppercase `__EMSCRIPTEN_MAJOR__` macro forms used since Emscripten
5.0.1, where the lowercase names became non-integer aliases.

Link: https://github.com/emscripten-core/emscripten/blob/4483d70a78098ed5d860dff2dc21f3025b2da2ee/system/lib/libc/musl/include/sys/epoll.h#L17
Link: https://github.com/emscripten-core/emscripten/blob/4483d70a78098ed5d860dff2dc21f3025b2da2ee/system/lib/libc/musl/include/sys/epoll.h#L70-L74
Link: emscripten-core/emscripten#27206
Link: emscripten-core/emscripten#27207

Author: guybedford

libc-test/build/main.rs

@@ -3211,6 +3211,9 @@ fn test_emscripten(t: &Target) {
         "stdio.h",
         "stdlib.h",
         "string.h",
+        // `sys/epoll.h` was restored in Emscripten 6.0.2
+        // https://github.com/emscripten-core/emscripten/pull/27206
+        (emscripten >= (6, 0, 2), "sys/epoll.h"),
         "sys/file.h",
         "sys/ioctl.h",
         "sys/ipc.h",
@@ -3284,15 +3287,15 @@ fn test_emscripten(t: &Target) {
         }
     });
 
-    cfg.skip_union(|union_| {
+    cfg.skip_union(move |union_| {
         match union_.ident() {
             // FIXME(emscripten): Investigate why the test fails.
             // Skip for now to unblock CI.
             "sigval" => true,
 
-            // No epoll support
-            // https://github.com/emscripten-core/emscripten/issues/5033
-            ty if ty.starts_with("epoll") => true,
+            // `sys/epoll.h` was restored in Emscripten 6.0.2
+            // https://github.com/emscripten-core/emscripten/pull/27206
+            ty if ty.starts_with("epoll") => emscripten < (6, 0, 2),
 
             _ => false,
         }
@@ -3316,9 +3319,9 @@ fn test_emscripten(t: &Target) {
             // Extern types
             "DIR" | "FILE" | "fpos_t" | "fpos64_t" | "timezone" => true,
 
-            // No epoll support
-            // https://github.com/emscripten-core/emscripten/issues/5033
-            ty if ty.starts_with("epoll") => true,
+            // `sys/epoll.h` was restored in Emscripten 6.0.2
+            // https://github.com/emscripten-core/emscripten/pull/27206
+            ty if ty.starts_with("epoll") => emscripten < (6, 0, 2),
 
             ty if ty.starts_with("signalfd") => true,
             _ => false,
@@ -3332,7 +3335,15 @@ fn test_emscripten(t: &Target) {
             "execv" | "execve" | "execvp" | "execvpe" | "fexecve" | "wait4" => true,
 
             // Emscripten's `pthread_kill` used to only be linkable when building with `-pthread`
-            "pthread_kill" if emscripten < (6, 0) => true,
+            "pthread_kill" if emscripten < (6, 0, 0) => true,
+
+            // epoll support was added in Emscripten 6.0.8
+            // https://github.com/emscripten-core/emscripten/pull/27207
+            "epoll_create" | "epoll_create1" | "epoll_ctl" | "epoll_wait" | "epoll_pwait"
+                if emscripten < (6, 0, 8) =>
+            {
+                true
+            }
 
             _ => false,
         }
@@ -3343,9 +3354,9 @@ fn test_emscripten(t: &Target) {
             // FIXME(emscripten): emscripten uses different constants to constructs these
             n if n.contains("__SIZEOF_PTHREAD") => true,
 
-            // No epoll support
-            // https://github.com/emscripten-core/emscripten/issues/5033
-            n if n.starts_with("EPOLL") => true,
+            // `sys/epoll.h` was restored in Emscripten 6.0.2
+            // https://github.com/emscripten-core/emscripten/pull/27206
+            n if n.starts_with("EPOLL") => emscripten < (6, 0, 2),
 
             // No ptrace.h
             // https://github.com/emscripten-core/emscripten/pull/17704
@@ -6283,7 +6294,7 @@ struct Versions {
     openbsd: Option<(u32, u32)>,
     netbsd: Option<(u32, u32)>,
     apple: Option<(u32, u32)>,
-    emscripten: Option<(u32, u32)>,
+    emscripten: Option<(u32, u32, u32)>,
     wasi_sdk: Option<(u32, WasiVersion)>,
     /// Android API level (no minor version).
     android: Option<u32>,
@@ -6338,7 +6349,7 @@ impl Versions {
             #endif
 
             #ifdef __EMSCRIPTEN__
-            /* Provides __EMSCRIPTEN_MAJOR__, __EMSCRIPTEN_MINOR__ */
+            /* Provides __EMSCRIPTEN_major__, __EMSCRIPTEN_minor__, __EMSCRIPTEN_tiny__ */
             #include "emscripten/version.h"
             #endif
 
@@ -6433,11 +6444,23 @@ impl Versions {
                     let minor: u32 = caps[2].parse().unwrap();
                     ret.openbsd = Some((major, minor));
                 }
-                "__EMSCRIPTEN_major__" => {
-                    ret.emscripten.get_or_insert_default().0 = value.parse().unwrap()
+                // Versions before 5.0.1 define the lowercase names as integers; 5.0.1 and
+                // later define the uppercase names as integers and the lowercase names as
+                // non-integer aliases of them.
+                "__EMSCRIPTEN_major__" | "__EMSCRIPTEN_MAJOR__" => {
+                    if let Ok(v) = value.parse() {
+                        ret.emscripten.get_or_insert_default().0 = v;
+                    }
+                }
+                "__EMSCRIPTEN_minor__" | "__EMSCRIPTEN_MINOR__" => {
+                    if let Ok(v) = value.parse() {
+                        ret.emscripten.get_or_insert_default().1 = v;
+                    }
                 }
-                "__EMSCRIPTEN_minor__" => {
-                    ret.emscripten.get_or_insert_default().1 = value.parse().unwrap()
+                "__EMSCRIPTEN_tiny__" | "__EMSCRIPTEN_TINY__" => {
+                    if let Ok(v) = value.parse() {
+                        ret.emscripten.get_or_insert_default().2 = v;
+                    }
                 }
                 "__wasi_sdk_major__" => {
                     ret.wasi_sdk.get_or_insert_default().0 = value.parse().unwrap()

libc-test/semver/emscripten.txt

@@ -1,5 +1,30 @@
 AT_EACCESS
+EPOLLERR
+EPOLLET
+EPOLLEXCLUSIVE
+EPOLLHUP
+EPOLLIN
+EPOLLMSG
+EPOLLONESHOT
+EPOLLOUT
+EPOLLPRI
+EPOLLRDBAND
+EPOLLRDHUP
+EPOLLRDNORM
+EPOLLWAKEUP
+EPOLLWRBAND
+EPOLLWRNORM
+EPOLL_CLOEXEC
+EPOLL_CTL_ADD
+EPOLL_CTL_DEL
+EPOLL_CTL_MOD
 SIGEV_THREAD_ID
+epoll_create
+epoll_create1
+epoll_ctl
+epoll_event
+epoll_pwait
+epoll_wait
 getentropy
 getgrgid
 getgrgid_r

src/unix/linux_like/emscripten/mod.rs

@@ -807,6 +807,8 @@ pub const O_TRUNC: c_int = 512;
 pub const O_NOATIME: c_int = 0o1000000;
 pub const O_CLOEXEC: c_int = 0x80000;
 
+pub const EPOLL_CLOEXEC: c_int = 0x80000;
+
 // Defined as wasi value.
 pub const EPERM: c_int = 63;
 pub const ENOENT: c_int = 44;
@@ -1477,6 +1479,22 @@ extern "C" {
         timeout: *const crate::timespec,
     ) -> c_int;
     pub fn faccessat(dirfd: c_int, pathname: *const c_char, mode: c_int, flags: c_int) -> c_int;
+    pub fn epoll_create(size: c_int) -> c_int;
+    pub fn epoll_create1(flags: c_int) -> c_int;
+    pub fn epoll_ctl(epfd: c_int, op: c_int, fd: c_int, event: *mut crate::epoll_event) -> c_int;
+    pub fn epoll_wait(
+        epfd: c_int,
+        events: *mut crate::epoll_event,
+        maxevents: c_int,
+        timeout: c_int,
+    ) -> c_int;
+    pub fn epoll_pwait(
+        epfd: c_int,
+        events: *mut crate::epoll_event,
+        maxevents: c_int,
+        timeout: c_int,
+        sigmask: *const crate::sigset_t,
+    ) -> c_int;
 }
 
 // Alias <foo> to <foo>64 to mimic glibc's LFS64 support