[PATCH] std::quoted is too eager to clear the string

[Jonathan Wakely]

On 21/02/14 01:00 +0100, Lars Gullik Bjønnes wrote:
>
> * include/std/iomanip (_Quoted_string operator>>): Do not clear
>   string if input is not quoted.
>
>Currently the string is cleared regardless of
>how the string is handled. This patch just
>moves the clearing down so that we do not clear
>it if we are not going to quote the string
>(i.e. let operator>> handle the clearing if needed)
>and also not if we encounter any stream error.
>
>This has been reported as (bug 60270).
>
>I have no GCC paperwork in order, but I expect this change
>to be simple enough to not require that.

I'm committing this (Lars's patch and my testcase) now since it's a
necessary fix for a new, experimental feature, so I don't see any
point in releasing it broken then having to fix it in two branches.

Tested x86_64-linux, committed to trunk.
-------------- next part --------------
commit d5c77024ad042628249dc0c38c87a75f2cde5f36
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Mar 31 19:27:33 2014 +0100

    2014-03-31  Lars Gullik Bjønnes  <larsbj@gullik.org>
    	    Jonathan Wakely  <jwakely@redhat.com>
    
    	PR libstdc++/60270
    	* include/std/iomanip (_Quoted_string operator>>): Do not clear
    	string if input is not quoted.
    	* testsuite/27_io/manipulators/standard/char/60270.cc: New.

diff --git a/libstdc++-v3/include/std/iomanip b/libstdc++-v3/include/std/iomanip
index b2c7b95..73822db 100644
--- a/libstdc++-v3/include/std/iomanip
+++ b/libstdc++-v3/include/std/iomanip
@@ -415,8 +415,6 @@ _GLIBCXX_END_NAMESPACE_VERSION
 		 const _Quoted_string<basic_string<_CharT, _Traits, _Alloc>&,
 				      _CharT>& __str)
       {
-	__str._M_string.clear();
-
 	_CharT __c;
 	__is >> __c;
 	if (!__is.good())
@@ -427,6 +425,7 @@ _GLIBCXX_END_NAMESPACE_VERSION
 	    __is >> __str._M_string;
 	    return __is;
 	  }
+	__str._M_string.clear();
 	std::ios_base::fmtflags __flags
 	  = __is.flags(__is.flags() & ~std::ios_base::skipws);
 	do
diff --git a/libstdc++-v3/testsuite/27_io/manipulators/standard/char/60270.cc b/libstdc++-v3/testsuite/27_io/manipulators/standard/char/60270.cc
new file mode 100644
index 0000000..b2b213b
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/manipulators/standard/char/60270.cc
@@ -0,0 +1,38 @@
+// { dg-do run }
+// { dg-options "-std=gnu++14" }
+
+// Copyright (C) 2014 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/>.
+
+// 27.7.6 - Quoted manipulators		[quoted.manip]
+
+// libstdc++/60270
+
+#include <string>
+#include <sstream>
+#include <iomanip>
+#include <testsuite_hooks.h>
+
+int main()
+{
+  std::istringstream in;
+  std::string s = "xxx";
+  in >> s;
+  VERIFY( !s.empty() );
+  in >> std::quoted(s);
+  VERIFY( !s.empty() );
+}