libstdc++: Fix std::match_results::end() for failed matches [PR102667]

The end() function needs to consider whether the underlying vector is
empty, not whether the match_results object is empty. That's because the
underlying vector will always contain at least three elements for a
match_results object that is "ready". It contains three extra elements
which are stored in the vector but are not considered part of sequence,
and so should not be part of the [begin(),end()) range.

libstdc++-v3/ChangeLog:

	PR libstdc++/102667
	* include/bits/regex.h (match_result::empty()): Optimize by
	calling the base function directly.
	(match_results::end()): Check _Base_type::empty() not empty().
	* testsuite/28_regex/match_results/102667.C: New test.

(cherry picked from commit 84088dc4bb6a546c896a068dc201463493babf43)

diff --git a/libstdc++-v3/include/bits/regex.h b/libstdc++-v3/include/bits/regex.h
index ac10fa184c651b9cb0151f319f4830d1b699d180..a2eede6f3e4af24ad0e9a504b5c9a811fb9d898a 100644 (file)
--- a/libstdc++-v3/include/bits/regex.h
+++ b/libstdc++-v3/include/bits/regex.h
@@ -1804,7 +1804,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        */
       _GLIBCXX_NODISCARD bool
       empty() const noexcept
-      { return size() == 0; }
+      { return _Base_type::size() <= 3; }
 
       ///@}
 
@@ -1922,7 +1922,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        */
       const_iterator
       end() const noexcept
-      { return _Base_type::end() - (empty() ? 0 : 3); }
+      { return _Base_type::end() - (_Base_type::empty() ? 0 : 3); }
 
       /**
        * @brief Gets an iterator to one-past-the-end of the collection.

diff --git a/libstdc++-v3/testsuite/28_regex/match_results/102667.C b/libstdc++-v3/testsuite/28_regex/match_results/102667.C
new file mode 100644 (file)
index 0000000..9e38c9e
--- /dev/null
+++ b/libstdc++-v3/testsuite/28_regex/match_results/102667.C
@@ -0,0 +1,39 @@
+// { dg-do run { target c++11 } }
+
+#include <regex>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  std::cmatch sm;
+  VERIFY( sm.empty() );
+  VERIFY( sm.size() == 0 );
+  VERIFY( sm.begin() == sm.end() );  // PR libstdc++/83600
+
+  bool matched = std::regex_match("a", sm, std::regex("b"));
+  VERIFY( ! matched );
+  VERIFY( sm.ready() );
+  VERIFY( sm.empty() );
+  VERIFY( sm.size() == 0 );
+  VERIFY( sm.begin() == sm.end() ); // PR libstdc++/102667
+
+  matched = std::regex_match("a", sm, std::regex("a"));
+  VERIFY( matched );
+  VERIFY( sm.ready() );
+  VERIFY( ! sm.empty() );
+  VERIFY( sm.size() == 1 );
+  VERIFY( (sm.end() - sm.begin()) == 1 );
+
+  matched = std::regex_search("abcd", sm, std::regex("(b)(c)"));
+  VERIFY( matched );
+  VERIFY( sm.ready() );
+  VERIFY( ! sm.empty() );
+  VERIFY( sm.size() == 3 );
+  VERIFY( (sm.end() - sm.begin()) == 3 );
+}
+
+int main()
+{
+  test01();
+}