Fix GH-10239: proc_close after proc_get_status always returns -1

The waitpid function only works once when a process is exited.
Cache the result so subsequent status reads succeed.

Author: nielsdos

ext/standard/proc_open.c

@@ -226,6 +226,28 @@ static void _php_free_envp(php_process_env env)
 }
 /* }}} */
 
+#if HAVE_SYS_WAIT_H
+static pid_t waitpid_cached(php_process_handle *proc, int *wait_status, int options)
+{
+	if (proc->has_stored_exit_wait_status) {
+		*wait_status = proc->stored_exit_wait_status_value;
+		return proc->child;
+	}
+
+	pid_t wait_pid = waitpid(proc->child, wait_status, options);
+
+	/* The "exit" status is the final status of the process.
+	 * If we were to store the status unconditionally,
+	 * we would return stale statuses in the future after the process continues. */
+	if (wait_pid > 0 && WIFEXITED(*wait_status)) {
+		proc->has_stored_exit_wait_status = true;
+		proc->stored_exit_wait_status_value = *wait_status;
+	}
+
+	return wait_pid;
+}
+#endif
+
 /* {{{ proc_open_rsrc_dtor
  * Free `proc` resource, either because all references to it were dropped or because `pclose` or
  * `proc_close` were called */
@@ -270,7 +292,7 @@ static void proc_open_rsrc_dtor(zend_resource *rsrc)
 		waitpid_options = WNOHANG;
 	}
 	do {
-		wait_pid = waitpid(proc->child, &wstatus, waitpid_options);
+		wait_pid = waitpid_cached(proc, &wstatus, waitpid_options);
 	} while (wait_pid == -1 && errno == EINTR);
 
 	if (wait_pid <= 0) {
@@ -383,7 +405,7 @@ PHP_FUNCTION(proc_get_status)
 	exitcode = running ? -1 : wstatus;
 
 #elif HAVE_SYS_WAIT_H
-	wait_pid = waitpid(proc->child, &wstatus, WNOHANG|WUNTRACED);
+	wait_pid = waitpid_cached(proc, &wstatus, WNOHANG|WUNTRACED);
 
 	if (wait_pid == proc->child) {
 		if (WIFEXITED(wstatus)) {
@@ -1244,6 +1266,9 @@ PHP_FUNCTION(proc_open)
 	proc->childHandle = childHandle;
 #endif
 	proc->env = env;
+#if HAVE_SYS_WAIT_H
+	proc->has_stored_exit_wait_status = false;
+#endif
 
 	/* Clean up all the child ends and then open streams on the parent
 	 *   ends, where appropriate */

ext/standard/proc_open.h

@@ -43,4 +43,10 @@ typedef struct _php_process_handle {
 	zend_resource **pipes;
 	zend_string *command;
 	php_process_env env;
+#if HAVE_SYS_WAIT_H
+	/* We can only request the status once before it becomes unavailable.
+	 * Store the result so we can request it multiple times. */
+	int stored_exit_wait_status_value;
+	bool has_stored_exit_wait_status;
+#endif
 } php_process_handle;