internal: prevent early exit processes from being zombies (#11995)

Prevent `exec`/`exec-once` processes which terminate very early
(before Hyprland declares that it does not want to reap zombies)
from getting stuck as zombie processes.

hyprtester/src/tests/main/misc.cpp

@@ -194,6 +194,10 @@ static bool test() {
         EXPECT_CONTAINS(str, "fullscreen: 2");
     }
 
+    // Ensure that the process autostarted in the config does not
+    // become a zombie even if it terminates very quickly.
+    EXPECT(Tests::execAndGet("pgrep -f 'sleep 0'").empty(), true);
+
     // kill all
     NLog::log("{}Killing all windows", Colors::YELLOW);
     Tests::killAllWindows();

hyprtester/test.conf

@@ -46,6 +46,7 @@ $menu = wofi --show drun
 # Autostart necessary processes (like notifications daemons, status bars, etc.)
 # Or execute your favorite apps at launch like this:
 
+exec-once = sleep 0  # Terminates very quickly
 # exec-once = $terminal
 # exec-once = nm-applet &
 # exec-once = waybar & hyprpaper & firefox

src/main.cpp

@@ -187,6 +187,8 @@ int main(int argc, char** argv) {
         return 1;
     }
 
+    reapZombieChildrenAutomatically();
+
     g_pCompositor->initServer(socketName, socketFd);
 
     if (verifyConfig)
@@ -195,8 +197,6 @@ int main(int argc, char** argv) {
     if (!envEnabled("HYPRLAND_NO_RT"))
         NInit::gainRealTime();
 
-    reapZombieChildrenAutomatically();
-
     Debug::log(LOG, "Hyprland init finished.");
 
     // If all's good to go, start.