exec: Spawn processes as direct children (#11735)

* exec: Spawn processes as direct children

Spawn processes as children rather than grandchildren.
This way, spawned processes may track Hyprland's state
by watching their parent, either directly or indirectly
(e.g., Linux's `PR_SET_PDEATH_SIG`).

Fixes #11728

* tests/exec: Add the test on process spawning

Add a test that ensures that:
- A spawned process remains a direct child of Hyprland;
- Upon termination, the process does not become a zombie.

hyprtester/src/tests/main/exec.cpp

@@ -0,0 +1,64 @@
+#include "tests.hpp"
+#include "../../shared.hpp"
+#include "../../hyprctlCompat.hpp"
+#include <chrono>
+#include <thread>
+#include <hyprutils/os/Process.hpp>
+#include <hyprutils/memory/WeakPtr.hpp>
+#include "../shared.hpp"
+
+static int ret = 0;
+
+using namespace Hyprutils::OS;
+using namespace Hyprutils::Memory;
+
+#define UP CUniquePointer
+#define SP CSharedPointer
+
+static std::string execAndGet(const std::string& cmd) {
+    CProcess proc("/bin/sh", {"-c", cmd});
+
+    if (!proc.runSync()) {
+        return "error";
+    }
+
+    return proc.stdOut();
+}
+
+static bool test() {
+    NLog::log("{}Testing process spawning", Colors::GREEN);
+
+    // Note: POSIX sleep does not support fractional seconds, so
+    // can't sleep for less than 1 second.
+    OK(getFromSocket("/dispatch exec sleep 1"));
+
+    // Ensure that sleep is our child
+    const std::string sleepPidS = execAndGet("pgrep sleep");
+    pid_t             sleepPid;
+    try {
+        sleepPid = std::stoull(sleepPidS);
+    } catch (...) {
+        NLog::log("{}Sleep was not spawned or several sleeps are running: pgrep returned '{}'", Colors::RED, sleepPidS);
+        return false;
+    }
+
+    const std::string sleepParentComm = execAndGet("cat \"/proc/$(ps -o ppid:1= -p " + sleepPidS + ")/comm\"");
+    NLog::log("{}Expecting that sleep's parent is Hyprland", Colors::YELLOW);
+    EXPECT_CONTAINS(sleepParentComm, "Hyprland");
+
+    std::this_thread::sleep_for(std::chrono::seconds(1));
+
+    // Ensure that sleep did not become a zombie
+    EXPECT(Tests::processAlive(sleepPid), false);
+
+    // kill all
+    NLog::log("{}Killing all windows", Colors::YELLOW);
+    Tests::killAllWindows();
+
+    NLog::log("{}Expecting 0 windows", Colors::YELLOW);
+    EXPECT(Tests::windowCount(), 0);
+
+    return !ret;
+}
+
+REGISTER_TEST_FN(test)