libstdc++: Define std::sub_match::swap member function (LWG 3204)

This was approved at the C++ meeting in February.

libstdc++-v3/ChangeLog:

	* include/bits/regex.h (sub_match::swap): New function.
	* testsuite/28_regex/sub_match/lwg3204.cc: New test.

1 files changed, 38 insertions, 0 deletions

diff --git a/libstdc++-v3/testsuite/28_regex/sub_match/lwg3204.cc b/libstdc++-v3/testsuite/28_regex/sub_match/lwg3204.cc
new file mode 100644
index 0000000..58ef0df
--- /dev/null
+++ b/libstdc++-v3/testsuite/28_regex/sub_match/lwg3204.cc
@@ -0,0 +1,38 @@
+// { dg-do run { target c++11 } }
+#include <regex>
+#include <testsuite_hooks.h>
+
+// LWG 3204. sub_match::swap only swaps the base class
+
+int main()
+{
+  std::sub_match<const char*> a, b;
+  a.matched = true;
+  a.swap(b);
+  VERIFY( ! a.matched );
+  VERIFY( b.matched );
+}
+
+struct iter
+{
+  using value_type = char;
+  using difference_type = long;
+  using pointer = const char*;
+  using reference = const char&;
+  using iterator_category = std::bidirectional_iterator_tag;
+
+  iter();
+  iter(const iter&) noexcept(false);
+
+  iter& operator++();
+  iter operator++(int);
+  iter& operator--();
+  iter operator--(int);
+  reference operator*() const;
+  pointer operator->() const;
+};
+
+using CS = std::csub_match;
+static_assert( noexcept(std::declval<CS&>().swap(std::declval<CS&>())) );
+using IS = std::sub_match<iter>;
+static_assert( ! noexcept(std::declval<IS&>().swap(std::declval<IS&>())) );