Restore previous group start after a failed non-capturing group (#4002)

Fixes #3934.

JerryScript-DCO-1.0-Signed-off-by: Dániel Bátyai daniel.batyai@h-lab.eu

jerry-core/ecma/operations/ecma-regexp-object.c

@@ -694,6 +694,7 @@ ecma_regexp_run (ecma_regexp_ctx_t *re_ctx_p, /**< RegExp matcher context */
         group_p->subcapture_start = re_get_value (&bc_p);
         group_p->subcapture_count = re_get_value (&bc_p);
 
+        const lit_utf8_byte_t *const saved_begin_p = group_p->begin_p;
         const uint32_t saved_iterator = group_p->iterator;
         const uint32_t qmin = re_get_value (&bc_p);
 
@@ -720,6 +721,7 @@ ecma_regexp_run (ecma_regexp_ctx_t *re_ctx_p, /**< RegExp matcher context */
 
         if (matched_p == NULL)
         {
+          group_p->begin_p = saved_begin_p;
           goto fail;
         }
 

tests/jerry/regression-test-issue-3934.js

@@ -0,0 +1,19 @@
+// Copyright JS Foundation and other contributors, http://js.foundation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+var r = /(?:(?:^b?)*)*a/.exec("bbba")
+
+assert (r !== null);
+assert (r.index === 3);
+assert (r[0] === "a");