[Patch, regex, libstdc++/70745] Fix match_not_bow and match_not_eow

[Tim Shen]

Bootstrapped and tested on x86-pc-linux-gnu debug.

It is a conformance fix, but I don't think it's very important. I'm
happy to backport it to gcc 5/4.9, but if it's not considered
necessary, I'm Ok as well.

Thanks!


-- 
Regards,
Tim Shen

commit 7f4f729d5dd80050ff966398e28909a40fb57932
Author: Tim Shen <tims...@google.com>
Date:   Thu Apr 21 21:02:11 2016 -0700

        PR libstdc++/70745
        * include/bits/regex_executor.tcc (_Executor<>::_M_word_boundary):
        Fix the match_not_bow and match_not_eow behavior.
        * testsuite/28_regex/regression.cc: Add testcase.

diff --git a/libstdc++-v3/include/bits/regex_executor.tcc 
b/libstdc++-v3/include/bits/regex_executor.tcc
index 2abd020..6bbcb1b 100644
--- a/libstdc++-v3/include/bits/regex_executor.tcc
+++ b/libstdc++-v3/include/bits/regex_executor.tcc
@@ -413,6 +413,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
     _M_word_boundary() const
     {
+      if (_M_current == _M_begin && (_M_flags & 
regex_constants::match_not_bow))
+       return false;
+      if (_M_current == _M_end && (_M_flags & regex_constants::match_not_eow))
+       return false;
+
       bool __left_is_word = false;
       if (_M_current != _M_begin
          || (_M_flags & regex_constants::match_prev_avail))
@@ -424,13 +429,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       bool __right_is_word =
         _M_current != _M_end && _M_is_word(*_M_current);
 
-      if (__left_is_word == __right_is_word)
-       return false;
-      if (__left_is_word && !(_M_flags & regex_constants::match_not_eow))
-       return true;
-      if (__right_is_word && !(_M_flags & regex_constants::match_not_bow))
-       return true;
-      return false;
+      return __left_is_word != __right_is_word;
     }
 
 _GLIBCXX_END_NAMESPACE_VERSION
diff --git a/libstdc++-v3/testsuite/28_regex/regression.cc 
b/libstdc++-v3/testsuite/28_regex/regression.cc
index c9a3402..d367c8b 100644
--- a/libstdc++-v3/testsuite/28_regex/regression.cc
+++ b/libstdc++-v3/testsuite/28_regex/regression.cc
@@ -45,7 +45,20 @@ test02()
       "/ghci"
     };
   auto rx = std::regex(re_str, std::regex_constants::grep | 
std::regex_constants::icase);
-  VERIFY(std::regex_search("/abcd", rx));
+  VERIFY(regex_search_debug("/abcd", rx));
+}
+
+void
+test03()
+{
+  bool test __attribute__((unused)) = true;
+
+  VERIFY(regex_match_debug("a.", regex(R"(a\b.)"), 
regex_constants::match_not_eow));
+  VERIFY(regex_match_debug(".a", regex(R"(.\ba)"), 
regex_constants::match_not_bow));
+  VERIFY(regex_search_debug("a", regex(R"(^\b)")));
+  VERIFY(regex_search_debug("a", regex(R"(\b$)")));
+  VERIFY(!regex_search_debug("a", regex(R"(^\b)"), 
regex_constants::match_not_bow));
+  VERIFY(!regex_search_debug("a", regex(R"(\b$)"), 
regex_constants::match_not_eow));
 }
 
 int
@@ -53,6 +66,7 @@ main()
 {
   test01();
   test02();
+  test03();
   return 0;
 }