Fixed bug #77738 (Nullptr deref in zend_compile_expr)

Author: laruence

NEWS

@@ -3,6 +3,7 @@ PHP                                                                        NEWS
 ?? ??? 2019, PHP 7.2.17
 
 - Core:
+  . Fixed bug #77738 (Nullptr deref in zend_compile_expr). (Laruence)
   . Fixed bug #77660 (Segmentation fault on break 2147483648). (Laruence)
   . Fixed bug #77652 (Anonymous classes can lose their interface information).
     (Nikita)

Zend/tests/bug77738.phpt

@@ -0,0 +1,8 @@
+--TEST--
+Bug #77738 (Nullptr deref in zend_compile_expr)
+--FILE--
+<?php
+__COMPILER_HALT_OFFSET__;
+; // <- important
+--EXPECTF--
+Warning: Use of undefined constant __COMPILER_HALT_OFFSET__ - assumed '__COMPILER_HALT_OFFSET__' %sbug77738.php on line %d

Zend/zend_compile.c

@@ -7673,11 +7673,11 @@ void zend_compile_const(znode *result, zend_ast *ast) /* {{{ */
 	if (zend_string_equals_literal(resolved_name, "__COMPILER_HALT_OFFSET__") || (name_ast->attr != ZEND_NAME_RELATIVE && zend_string_equals_literal(orig_name, "__COMPILER_HALT_OFFSET__"))) {
 		zend_ast *last = CG(ast);
 
-		while (last->kind == ZEND_AST_STMT_LIST) {
+		while (last && last->kind == ZEND_AST_STMT_LIST) {
 			zend_ast_list *list = zend_ast_get_list(last);
 			last = list->child[list->children-1];
 		}
-		if (last->kind == ZEND_AST_HALT_COMPILER) {
+		if (last && last->kind == ZEND_AST_HALT_COMPILER) {
 			result->op_type = IS_CONST;
 			ZVAL_LONG(&result->u.constant, Z_LVAL_P(zend_ast_get_zval(last->child[0])));
 			zend_string_release(resolved_name);