Don't treat expression exit as terminator

Same as with throw expressions, this may remove later temporary
consuming instructions and thus eliminate live ranges, resulting
in a memory leak. We make use of the same hack and don't consider
exit a terminator if used in an expression context.

Author: nikic

Zend/Optimizer/zend_cfg.c

@@ -299,13 +299,13 @@ ZEND_API int zend_build_cfg(zend_arena **arena, const zend_op_array *op_array, u
 			case ZEND_RETURN:
 			case ZEND_RETURN_BY_REF:
 			case ZEND_GENERATOR_RETURN:
-			case ZEND_EXIT:
 			case ZEND_MATCH_ERROR:
 			case ZEND_VERIFY_NEVER_TYPE:
 				if (i + 1 < op_array->last) {
 					BB_START(i + 1);
 				}
 				break;
+			case ZEND_EXIT:
 			case ZEND_THROW:
 				/* Don't treat THROW as terminator if it's used in expression context,
 				 * as we may lose live ranges when eliminating unreachable code. */

Zend/tests/throw/leaks.phpt

@@ -23,6 +23,9 @@ try {
 }
 var_dump(error_reporting());
 
+// Exit also unwinds and thus has the same basic problem.
+new stdClass(exit);
+
 ?>
 --EXPECT--
 Caught

Zend/zend_compile.c

@@ -9045,17 +9045,21 @@ static void zend_compile_print(znode *result, zend_ast *ast) /* {{{ */
 static void zend_compile_exit(znode *result, zend_ast *ast) /* {{{ */
 {
 	zend_ast *expr_ast = ast->child[0];
+	znode expr_node;
 
 	if (expr_ast) {
-		znode expr_node;
 		zend_compile_expr(&expr_node, expr_ast);
-		zend_emit_op(NULL, ZEND_EXIT, &expr_node, NULL);
 	} else {
-		zend_emit_op(NULL, ZEND_EXIT, NULL, NULL);
+		expr_node.op_type = IS_UNUSED;
 	}
 
-	result->op_type = IS_CONST;
-	ZVAL_TRUE(&result->u.constant);
+	zend_op *opline = zend_emit_op(NULL, ZEND_EXIT, &expr_node, NULL);
+	if (result) {
+		/* Mark this as an "expression throw" for opcache. */
+		opline->extended_value = ZEND_THROW_IS_EXPR;
+		result->op_type = IS_CONST;
+		ZVAL_TRUE(&result->u.constant);
+	}
 }
 /* }}} */
 
@@ -9999,6 +10003,7 @@ static void zend_compile_stmt(zend_ast *ast) /* {{{ */
 			zend_compile_halt_compiler(ast);
 			break;
 		case ZEND_AST_THROW:
+		case ZEND_AST_EXIT:
 			zend_compile_expr(NULL, ast);
 			break;
 		default: