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.

Closes GH-10250

Author: nielsdos

NEWS

@@ -116,6 +116,7 @@ PHP                                                                        NEWS
     starting tokenisation. (David Carlier)
   . password_hash() will now chain the original RandomException to the ValueError
     on salt generation failure. (timwolla)
+  . Fix GH-10239 (proc_close after proc_get_status always returns -1). (nielsdos)
 
 - Streams:
   . Fixed bug #51056: blocking fread() will block even if data is available.

UPGRADING

@@ -26,6 +26,13 @@ PHP 8.3 UPGRADE NOTES
     (`fiber.stack_size-zend.reserved_stack_size` for fibers).
   . Class constants can now be accessed dynamically using the C::{$name} syntax.
     RFC: https://wiki.php.net/rfc/dynamic_class_constant_fetch
+  . Executing proc_get_status() multiple times will now always return the right
+    value on posix systems. Previously, only the first call of the function
+    returned the right value. Executing proc_close() after proc_get_status() will
+    now also return the right exit code. Previously this would return -1.
+    Internally, this works by caching the result on posix systems. If you want
+    the old behaviour, you can check the "cached" key in the array returned by
+    proc_get_status() to check whether the result was cached.
 
 - FFI:
   . C functions that have a return type of void now return null instead of

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_cached_exit_wait_status) {
+		*wait_status = proc->cached_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 cache the status unconditionally,
+	 * we would return stale statuses in the future after the process continues. */
+	if (wait_pid > 0 && WIFEXITED(*wait_status)) {
+		proc->has_cached_exit_wait_status = true;
+		proc->cached_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) {
@@ -382,8 +404,12 @@ PHP_FUNCTION(proc_get_status)
 	running = wstatus == STILL_ACTIVE;
 	exitcode = running ? -1 : wstatus;
 
+	/* The status is always available on Windows and will always read the same,
+	 * even if the child has already exited. This is because the result stays available
+	 * until the child handle is closed. Hence no caching is used on Windows. */
+	add_assoc_bool(return_value, "cached", false);
 #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)) {
@@ -404,6 +430,8 @@ PHP_FUNCTION(proc_get_status)
 		 * looking for either does not exist or is not a child of this process */
 		running = 0;
 	}
+
+	add_assoc_bool(return_value, "cached", proc->has_cached_exit_wait_status);
 #endif
 
 	add_assoc_bool(return_value, "running", running);
@@ -1250,6 +1278,9 @@ PHP_FUNCTION(proc_open)
 	proc->childHandle = childHandle;
 #endif
 	proc->env = env;
+#if HAVE_SYS_WAIT_H
+	proc->has_cached_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.
+	 * Cache the result so we can request it multiple times. */
+	int cached_exit_wait_status_value;
+	bool has_cached_exit_wait_status;
+#endif
 } php_process_handle;

ext/standard/tests/general_functions/bug39322.phpt

@@ -24,11 +24,13 @@ echo "Done!\n";
 
 ?>
 --EXPECTF--
-array(8) {
+array(9) {
   ["command"]=>
   string(14) "/bin/sleep 120"
   ["pid"]=>
   int(%d)
+  ["cached"]=>
+  bool(false)
   ["running"]=>
   bool(false)
   ["signaled"]=>

ext/standard/tests/general_functions/gh10239_1.phpt

@@ -0,0 +1,18 @@
+--TEST--
+GH-10239 (proc_close after proc_get_status always returns -1)
+--SKIPIF--
+<?php
+if (PHP_OS != "Linux") die("skip, only for linux");
+if (getenv("SKIP_SLOW_TESTS")) die('skip slow test');
+?>
+--FILE--
+<?php
+$p = proc_open('sleep 1', array(), $foo);
+do {
+    usleep(100000);
+    $s = proc_get_status($p);
+} while ($s['running']);
+echo proc_close($p), PHP_EOL;
+?>
+--EXPECT--
+0

ext/standard/tests/general_functions/gh10239_2.phpt

@@ -0,0 +1,55 @@
+--TEST--
+GH-10239 (proc_close after proc_get_status always returns -1)
+--SKIPIF--
+<?php
+if (PHP_OS != "Linux") die("skip, only for linux");
+if (getenv("SKIP_SLOW_TESTS")) die('skip slow test');
+?>
+--FILE--
+<?php
+$p = proc_open('false', array(), $foo);
+usleep(2 * 1000 * 1000);
+var_dump(proc_get_status($p));
+var_dump(proc_get_status($p));
+?>
+--EXPECTF--
+array(9) {
+  ["command"]=>
+  string(5) "false"
+  ["pid"]=>
+  int(%d)
+  ["cached"]=>
+  bool(true)
+  ["running"]=>
+  bool(false)
+  ["signaled"]=>
+  bool(false)
+  ["stopped"]=>
+  bool(false)
+  ["exitcode"]=>
+  int(1)
+  ["termsig"]=>
+  int(0)
+  ["stopsig"]=>
+  int(0)
+}
+array(9) {
+  ["command"]=>
+  string(5) "false"
+  ["pid"]=>
+  int(%d)
+  ["cached"]=>
+  bool(true)
+  ["running"]=>
+  bool(false)
+  ["signaled"]=>
+  bool(false)
+  ["stopped"]=>
+  bool(false)
+  ["exitcode"]=>
+  int(1)
+  ["termsig"]=>
+  int(0)
+  ["stopsig"]=>
+  int(0)
+}

ext/standard/tests/general_functions/proc_open02.phpt

@@ -32,11 +32,13 @@ echo "Done!\n";
 ?>
 --EXPECTF--
 bool(true)
-array(8) {
+array(9) {
   ["command"]=>
   string(10) "/bin/sleep"
   ["pid"]=>
   int(%d)
+  ["cached"]=>
+  bool(false)
   ["running"]=>
   bool(true)
   ["signaled"]=>
@@ -51,11 +53,13 @@ array(8) {
   int(0)
 }
 bool(true)
-array(8) {
+array(9) {
   ["command"]=>
   string(10) "/bin/sleep"
   ["pid"]=>
   int(%d)
+  ["cached"]=>
+  bool(false)
   ["running"]=>
   bool(false)
   ["signaled"]=>