QProcess/Unix: allow startDetached() to also use vfork()

The same arguments that applied to the regular process-starting code in
commit e1a787a76ed462e4ed49db78a40c6d7e272182d7 (6.4) apply here too.

Task-number: QTBUG-104493
Change-Id: Icfe44ecf285a480fafe4fffd174da1b05d0054bc
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Reviewed-by: Marcus Tillmanns <marcus.tillmanns@qt.io>

1 files changed, 7 insertions, 2 deletions

diff --git a/src/corelib/io/qprocess_unix.cpp b/src/corelib/io/qprocess_unix.cpp
index a6851b69e9..7ae28b84dd 100644
--- a/src/corelib/io/qprocess_unix.cpp
+++ b/src/corelib/io/qprocess_unix.cpp
@@ -1090,7 +1090,12 @@ bool QProcessPrivate::startDetached(qint64 *pid)
     // see startProcess() for more information
     PThreadCancelGuard cancelGuard;
 
-    pid_t childPid = fork();
+    auto doFork = [this]() {
+        if (useForkFlags(unixExtras.get()))
+            return fork;
+        QT_IGNORE_DEPRECATIONS(return vfork;)
+    }();
+    pid_t childPid = doFork();
     if (childPid == 0) {
         ::signal(SIGPIPE, SIG_DFL);     // reset the signal that we ignored
         ::setsid();
@@ -1105,7 +1110,7 @@ bool QProcessPrivate::startDetached(qint64 *pid)
             ::_exit(1);
         };
 
-        pid_t doubleForkPid = fork();
+        pid_t doubleForkPid = doFork();
         if (doubleForkPid == 0) {
             // Render channels configuration.
             commitChannels();