Add capacity check (only in debug mode)

Author: nielsdos

ext/opcache/ZendAccelerator.c

@@ -4765,6 +4765,9 @@ static int accel_finish_startup(void)
 
 			ZCG(mem_checksum_skip_list) = NULL;
 			ZCG(mem_checksum_skip_list_count) = 0;
+#if ZEND_DEBUG
+			ZCG(mem_checksum_skip_list_capacity) = 0;
+#endif
 
 			if (accel_preload(ZCG(accel_directives).preload, in_child) != SUCCESS) {
 				ret = FAILURE;

ext/opcache/ZendAccelerator.h

@@ -245,6 +245,13 @@ typedef struct _zend_accel_globals {
 
 	zend_accel_skip_list_entry *mem_checksum_skip_list;
 	uint32_t mem_checksum_skip_list_count;
+	/* We don't actually need the capacity because the skip list is preallocated to the right size.
+	 * We only use this in a debug build to check for bugs. If an assertion failure would ever trigger
+	 * for this field, then it's signifies a bug in the persistence code because the calculation and
+	 * actual size don't match. */
+#if ZEND_DEBUG
+	uint32_t mem_checksum_skip_list_capacity;
+#endif
 } zend_accel_globals;
 
 typedef struct _zend_string_table {

ext/opcache/zend_persist.c

@@ -93,6 +93,9 @@ static void mem_checksum_skip_list_add(void *p, uint32_t checked_area_size, uint
 	ZEND_ASSERT(ZCG(mem_checksum_skip_list) != NULL);
 	char *base_ptr = (char *) ZCG(current_persistent_script)->mem + sizeof(zend_persistent_script);
 	ZEND_ASSERT((char *) p >= base_ptr);
+#if ZEND_DEBUG
+	ZEND_ASSERT(ZCG(mem_checksum_skip_list_count) < ZCG(mem_checksum_skip_list_capacity));
+#endif
 	zend_accel_skip_list_entry *entry = &ZCG(mem_checksum_skip_list)[ZCG(mem_checksum_skip_list_count)++];
 	entry->offset = (char *) p - base_ptr;
 	entry->checked_area_size = checked_area_size;
@@ -1337,6 +1340,9 @@ zend_persistent_script *zend_accel_script_persist(zend_persistent_script *script
 
 	/* The skip list count is still set by the persist_calc routines, which always precedes a call to this function. */
 	ZCG(mem_checksum_skip_list) = safe_emalloc(ZCG(mem_checksum_skip_list_count), sizeof(zend_accel_skip_list_entry), 0);
+#if ZEND_DEBUG
+	ZCG(mem_checksum_skip_list_capacity) = ZCG(mem_checksum_skip_list_count);
+#endif
 	ZCG(mem_checksum_skip_list_count) = 0;
 
 	script->mem = ZCG(mem);