Leave errno unchanged by successful std::stoi etc

	* include/ext/string_conversions.h (__stoa): Save and restore errno.
	* testsuite/21_strings/basic_string/numeric_conversions/char/errno.cc:
	New.

From-SVN: r228249

libstdc++-v3/ChangeLog

 2015-09-29  Jonathan Wakely  <jwakely@redhat.com>
 
+	* include/ext/string_conversions.h (__stoa): Save and restore errno.
+	* testsuite/21_strings/basic_string/numeric_conversions/char/errno.cc:
+	New.
+
 	PR libstdc++/67583
 	* testsuite/27_io/basic_stringbuf/seekoff/char/1.cc: Fix sputn call
 	with mismatched arguments.

libstdc++-v3/include/ext/string_conversions.h

@@ -58,6 +58,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       _Ret __ret;
 
       _CharT* __endptr;
+      const int __saved_errno = errno;
       errno = 0;
       const _TRet __tmp = __convf(__str, &__endptr, __base...);
 
@@ -70,6 +71,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	std::__throw_out_of_range(__name);
       else
 	__ret = __tmp;
+      errno = __saved_errno;
 
       if (__idx)
 	*__idx = __endptr - __str;

libstdc++-v3/testsuite/21_strings/basic_string/numeric_conversions/char/errno.cc

+// Copyright (C) 2015 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++11" }
+// { dg-require-string-conversions "" }
+
+#include <string>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  errno = ERANGE;
+  std::stoi("42");
+  VERIFY( errno == ERANGE ); // errno should not be altered by successful call
+}
+
+int
+main()
+{
+  test01();
+}