Add fd3 support to runmake

src/tools/run-make-support/Cargo.toml

@@ -10,6 +10,7 @@ similar = "2.5.0"
 wasmparser = { version = "0.216", default-features = false, features = ["std"] }
 regex = "1.8" # 1.8 to avoid memchr 2.6.0, as 2.5.0 is pinned in the workspace
 gimli = "0.31.0"
+libc = "0.2"
 build_helper = { path = "../build_helper" }
 serde_json = "1.0"
 libc = "0.2"

src/tools/run-make-support/src/command.rs

@@ -151,6 +151,31 @@ impl Command {
         self
     }
 
+    /// Set an auxiliary stream passed to the process, besides the stdio streams.
+    #[cfg(unix)]
+    pub fn set_aux_fd<F: Into<std::os::fd::OwnedFd>>(
+        &mut self,
+        newfd: std::os::fd::RawFd,
+        fd: F,
+    ) -> &mut Self {
+        use std::os::fd::AsRawFd;
+        use std::os::unix::process::CommandExt;
+
+        let fd = fd.into();
+        unsafe {
+            self.cmd.pre_exec(move || {
+                let fd = fd.as_raw_fd();
+                let ret = if fd == newfd {
+                    libc::fcntl(fd, libc::F_SETFD, 0)
+                } else {
+                    libc::dup2(fd, newfd)
+                };
+                if ret == -1 { Err(std::io::Error::last_os_error()) } else { Ok(()) }
+            });
+        }
+        self
+    }
+
     /// Run the constructed command and assert that it is successfully run.
     ///
     /// By default, std{in,out,err} are [`Stdio::piped()`].

src/tools/run-make-support/src/macros.rs

@@ -80,6 +80,17 @@ macro_rules! impl_common_helpers {
                 self
             }
 
+            /// Set an auxiliary stream passed to the process, besides the stdio streams.
+            #[cfg(unix)]
+            pub fn set_aux_fd<F: Into<std::os::fd::OwnedFd>>(
+                &mut self,
+                newfd: std::os::fd::RawFd,
+                fd: F,
+            ) -> &mut Self {
+                self.cmd.set_aux_fd(newfd, fd);
+                self
+            }
+
             /// Run the constructed command and assert that it is successfully run.
             #[track_caller]
             pub fn run(&mut self) -> crate::command::CompletedProcess {

tests/run-make/jobserver-error/rmake.rs

@@ -19,22 +19,24 @@ fn main() {
         .run_fail()
         .stderr_utf8();
     diff().expected_file("cannot_open_fd.stderr").actual_text("actual", out).run();
-    // FIXME(Oneirical): Find how to use file descriptor "3" with run-make-support
-    // and pipe /dev/null into it.
-    // Original lines:
-    //
-    // bash -c 'echo "fn main() {}" | makeflags="--jobserver-auth=3,3" $(rustc) - 3</dev/null' \
-    // 2>&1 | diff not_a_pipe.stderr -
+
+    let out = rustc()
+        .stdin("fn main() {}")
+        .input("-")
+        .env("MAKEFLAGS", "--jobserver-auth=3,3")
+        .set_aux_fd(3, std::fs::File::open("/dev/null").unwrap())
+        .run()
+        .stderr_utf8();
+    diff().expected_file("not_a_pipe.stderr").actual_text("actual", out).run();
+
     // # this test randomly fails, see https://github.com/rust-lang/rust/issues/110321
-    // disabled:
-    // bash -c 'echo "fn main() {}" | makeflags="--jobserver-auth=3,3" $(rustc) - \
-    // 3< <(cat /dev/null)' 2>&1 | diff poisoned_pipe.stderr -
-    //
+    // let (readpipe, _) = std::pipe::pipe().unwrap();
     // let out = rustc()
     //     .stdin("fn main() {}")
     //     .input("-")
-    //     .env("MAKEFLAGS", "--jobserver-auth=0,0")
+    //     .env("MAKEFLAGS", "--jobserver-auth=3,3")
+    //     .set_fd3(readpipe)
     //     .run()
     //     .stderr_utf8();
-    // diff().expected_file("not_a_pipe.stderr").actual_text("actual", out).run();
+    // diff().expected_file("poisoned_pipe.stderr").actual_text("actual", out).run();
 }