ext/opcache/zend_shared_alloc: add assertions on "locked" flag

Let the PHP process crash if a bug causes incorrect locking calls.

Author: MaxKellermann

ext/opcache/zend_shared_alloc.c

@@ -453,6 +453,8 @@ void zend_shared_alloc_safe_unlock(void)
 
 void zend_shared_alloc_lock(void)
 {
+	ZEND_ASSERT(!ZCG(locked));
+
 #ifndef ZEND_WIN32
 	struct flock mem_write_lock;
 
@@ -490,6 +492,8 @@ void zend_shared_alloc_lock(void)
 
 void zend_shared_alloc_unlock(void)
 {
+	ZEND_ASSERT(ZCG(locked));
+
 #ifndef ZEND_WIN32
 	struct flock mem_write_unlock;