[PATCH] [libcxx] Fix match_results for alternatives

[Agustín Bergé]

Hi mclow.lists, EricWF,

Initialize submatch results to unmatched. They will not be modified for failed alternatives (they might not even be looked at), and would otherwise leave the pair of iterators value-initialized instead of pointing to the end of the searched sequence. Fixes PR22061.

http://reviews.llvm.org/D7111

Files:
  include/regex
  test/std/re/re.results/re.results.acc/index.pass.cpp

Index: include/regex
===================================================================
--- include/regex
+++ include/regex
@@ -5601,12 +5601,17 @@
     __node* __st = __start_.get();
     if (__st)
     {
+        sub_match<const _CharT*> __unmatched;
+        __unmatched.first   = __last;
+        __unmatched.second  = __last;
+        __unmatched.matched = false;
+
         __states.push_back(__state());
         __states.back().__do_ = 0;
         __states.back().__first_ = __first;
         __states.back().__current_ = __first;
         __states.back().__last_ = __last;
-        __states.back().__sub_matches_.resize(mark_count());
+        __states.back().__sub_matches_.resize(mark_count(), __unmatched);
         __states.back().__loop_data_.resize(__loop_count());
         __states.back().__node_ = __st;
         __states.back().__flags_ = __flags;
@@ -5746,12 +5751,17 @@
     __node* __st = __start_.get();
     if (__st)
     {
+        sub_match<const _CharT*> __unmatched;
+        __unmatched.first   = __last;
+        __unmatched.second  = __last;
+        __unmatched.matched = false;
+
         __states.push_back(__state());
         __states.back().__do_ = 0;
         __states.back().__first_ = __first;
         __states.back().__current_ = __first;
         __states.back().__last_ = __last;
-        __states.back().__sub_matches_.resize(mark_count());
+        __states.back().__sub_matches_.resize(mark_count(), __unmatched);
         __states.back().__loop_data_.resize(__loop_count());
         __states.back().__node_ = __st;
         __states.back().__flags_ = __flags;
Index: test/std/re/re.results/re.results.acc/index.pass.cpp
===================================================================
--- test/std/re/re.results/re.results.acc/index.pass.cpp
+++ test/std/re/re.results/re.results.acc/index.pass.cpp
@@ -21,7 +21,7 @@
 {
     std::match_results<const char*> m;
     const char s[] = "abcdefghijk";
-    assert(std::regex_search(s, m, std::regex("cd((e)fg)hi")));
+    assert(std::regex_search(s, m, std::regex("cd((e)fg)hi|(z)")));
 
     assert(m[0].first == s+2);
     assert(m[0].second == s+9);
@@ -42,6 +42,10 @@
     assert(m[4].first == s+11);
     assert(m[4].second == s+11);
     assert(m[4].matched == false);
+
+    assert(m[5].first == s+11);
+    assert(m[5].second == s+11);
+    assert(m[4].matched == false);
 }
 
 int main()

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