From 21839116ebc56b461914b7dd8dadff3f12423a8a Mon Sep 17 00:00:00 2001
From: Thibault Saunier <tsaunier@igalia.com>
Date: Thu, 19 Mar 2026 16:56:45 +0000
Subject: [PATCH] syscall: Accept O_NONBLOCK flag in pipe2

pipe2 only accepted O_CLOEXEC, rejecting O_NONBLOCK with ENOTSUP.
Accept O_NONBLOCK and set it on the created pipe streams.

This is needed by GLib's GWakeup which uses
pipe2(fds, O_CLOEXEC | O_NONBLOCK).
---
 src/lib/libsyscall.js | 8 +++++++-
 test/unistd/misc.c    | 8 ++++++++
 test/unistd/misc.out  | 4 ++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/src/lib/libsyscall.js b/src/lib/libsyscall.js
index 1e1976cf41875..7fe77e016ecd5 100644
--- a/src/lib/libsyscall.js
+++ b/src/lib/libsyscall.js
@@ -199,12 +199,18 @@ var SyscallsLibrary = {
     if (fdPtr == 0) {
       throw new FS.ErrnoError({{{ cDefs.EFAULT }}});
     }
-    if (flags && flags != {{{ cDefs.O_CLOEXEC }}}) {
+    var validFlags = {{{ cDefs.O_CLOEXEC }}} | {{{ cDefs.O_NONBLOCK }}};
+    if (flags & ~validFlags) {
       throw new FS.ErrnoError({{{ cDefs.ENOTSUP }}});
     }
 
     var res = PIPEFS.createPipe();
 
+    if (flags & {{{ cDefs.O_NONBLOCK }}}) {
+      FS.getStream(res.readable_fd).flags |= {{{ cDefs.O_NONBLOCK }}};
+      FS.getStream(res.writable_fd).flags |= {{{ cDefs.O_NONBLOCK }}};
+    }
+
     {{{ makeSetValue('fdPtr', 0, 'res.readable_fd', 'i32') }}};
     {{{ makeSetValue('fdPtr', 4, 'res.writable_fd', 'i32') }}};
 
diff --git a/test/unistd/misc.c b/test/unistd/misc.c
index 3efcbad477a63..190582957f200 100644
--- a/test/unistd/misc.c
+++ b/test/unistd/misc.c
@@ -86,6 +86,14 @@ int main() {
   printf("pipe2(bad): %d", pipe2(0, 0));
   printf(", errno: %d\n", errno);
   errno = 0;
+  printf("pipe2(O_NONBLOCK): %d", pipe2(pipe_arg, O_NONBLOCK));
+  printf(", errno: %d\n", errno);
+  printf("pipe2(O_NONBLOCK) read flags: %d\n", (fcntl(pipe_arg[0], F_GETFL) & O_NONBLOCK) != 0);
+  printf("pipe2(O_NONBLOCK) write flags: %d\n", (fcntl(pipe_arg[1], F_GETFL) & O_NONBLOCK) != 0);
+  errno = 0;
+  printf("pipe2(O_CLOEXEC|O_NONBLOCK): %d", pipe2(pipe_arg, O_CLOEXEC | O_NONBLOCK));
+  printf(", errno: %d\n", errno);
+  errno = 0;
 
   char* exec_argv[] = {"arg", 0};
   char* exec_env[] = {"a=b", 0};
diff --git a/test/unistd/misc.out b/test/unistd/misc.out
index 17e5b17ffa0e5..4ed4b37a3b5fd 100644
--- a/test/unistd/misc.out
+++ b/test/unistd/misc.out
@@ -15,6 +15,10 @@ pipe(good): 0, errno: 0
 pipe(bad): -1, errno: 21
 pipe2(good): 0, errno: 0
 pipe2(bad): -1, errno: 21
+pipe2(O_NONBLOCK): 0, errno: 0
+pipe2(O_NONBLOCK) read flags: 1
+pipe2(O_NONBLOCK) write flags: 1
+pipe2(O_CLOEXEC|O_NONBLOCK): 0, errno: 0
 execl: -1, errno: 45
 execle: -1, errno: 45
 execlp: -1, errno: 45