Bill Fisher: This patch fixes a bug where regex_iterator doesn't indicate when it's restarting in the middle of a string. This bug causes /^a/ to match in the middle of the string "aaaaaaa", during iteration.

My patch uses  to communicate when  is false.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@185950 91177308-0d34-0410-b5e6-96231b3b80d8

include/regex

diff --git a/include/regex b/include/regex
index 312ca11..36d5677 100644
--- a/include/regex
+++ b/include/regex
@@ -5773,7 +5773,8 @@
 {
     __m.__init(1 + mark_count(), __first, __last,
                                     __flags & regex_constants::__no_update_pos);
-    if (__match_at_start(__first, __last, __m, __flags, true))
+    if (__match_at_start(__first, __last, __m, __flags, 
+                                    !(__flags & regex_constants::__no_update_pos)))
     {
         __m.__prefix_.second = __m[0].first;
         __m.__prefix_.matched = __m.__prefix_.first != __m.__prefix_.second;