ext/pcntl: fix pcntl_signal_dispatch() stale tail pointer and exception handling.

close GH-21259

Author: devnexen

NEWS

@@ -50,6 +50,8 @@ PHP                                                                        NEWS
     on NetBSD/Solaris platforms. (David Carlier)
   . Fixed pcntl_signal() signal table registering the callback first
     OS-wise before the internal list. (David Carlier)
+  . Fixed pcntl_signal_dispatch() stale pointer and exception
+    handling. (David Carlier)
 
 - PDO_PGSQL:
   . Fixed bug GH-21055 (connection attribute status typo for GSS negotiation).

ext/pcntl/pcntl.c

@@ -1343,6 +1343,7 @@ void pcntl_signal_dispatch(void)
 
 	queue = PCNTL_G(head);
 	PCNTL_G(head) = NULL; /* simple stores are atomic */
+	PCNTL_G(tail) = NULL;
 
 	/* Allocate */
 	while (queue) {
@@ -1364,6 +1365,9 @@ void pcntl_signal_dispatch(void)
 #ifdef HAVE_STRUCT_SIGINFO_T
 				zval_ptr_dtor(&params[1]);
 #endif
+				if (EG(exception)) {
+					break;
+				}
 			}
 		}
 
@@ -1373,6 +1377,14 @@ void pcntl_signal_dispatch(void)
 		queue = next;
 	}
 
+	/* drain the remaining in case of exception thrown */
+	while (queue) {
+		next = queue->next;
+		queue->next = PCNTL_G(spares);
+		PCNTL_G(spares) = queue;
+		queue = next;
+	}
+
 	PCNTL_G(pending_signals) = 0;
 
 	/* Re-enable queue */

ext/pcntl/tests/pcntl_signal_dispatch_exception.phpt

@@ -0,0 +1,34 @@
+--TEST--
+pcntl_signal_dispatch() stops dispatching after handler throws exception
+--EXTENSIONS--
+pcntl
+posix
+--FILE--
+<?php
+
+$called = [];
+
+pcntl_signal(SIGUSR1, function ($signo) use (&$called) {
+    $called[] = 'SIGUSR1';
+    throw new \Exception('Exception in signal handler');
+});
+
+pcntl_signal(SIGUSR2, function ($signo) use (&$called) {
+    $called[] = 'SIGUSR2';
+});
+
+posix_kill(posix_getpid(), SIGUSR1);
+posix_kill(posix_getpid(), SIGUSR2);
+
+try {
+    pcntl_signal_dispatch();
+} catch (\Exception $e) {
+    echo $e->getMessage() . "\n";
+}
+
+echo "Handlers called: " . implode(', ', $called) . "\n";
+
+?>
+--EXPECT--
+Exception in signal handler
+Handlers called: SIGUSR1