rust: library: Add setsid method to CommandExt trait

Add a setsid method to the CommandExt trait so that callers can create
a process in a new session and process group whilst still using the
POSIX spawn fast path.

Co-Authored-By: Harvey Hunt <harveyhunt@fb.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/library/std/src/sys/process/unix/unix.rs b/library/std/src/sys/process/unix/unix.rs
index 4f595ac9a1c..9162573ba09 100644
--- a/library/std/src/sys/process/unix/unix.rs
+++ b/library/std/src/sys/process/unix/unix.rs
@@ -340,6 +340,10 @@ impl Command {
             cvt(libc::setpgid(0, pgroup))?;
         }
 
+        if self.get_setsid() {
+            cvt(libc::setsid())?;
+        }
+
         // emscripten has no signal support.
         #[cfg(not(target_os = "emscripten"))]
         {
@@ -741,6 +745,16 @@ impl Command {
                 flags |= libc::POSIX_SPAWN_SETSIGDEF;
             }
 
+            if self.get_setsid() {
+                cfg_if::cfg_if! {
+                    if #[cfg(all(target_os = "linux", target_env = "gnu"))] {
+                        flags |= libc::POSIX_SPAWN_SETSID;
+                    } else {
+                        return Ok(None);
+                    }
+                }
+            }
+
             cvt_nz(libc::posix_spawnattr_setflags(attrs.0.as_mut_ptr(), flags as _))?;
 
             // Make sure we synchronize access to the global `environ` resource