[Patch] Fix a latent bug in basic_stringbuf::seekpos

[Paolo Carlini <pcarlini at unitus dot it>]

Hi,

this is not so easy to trigger, since seekoff is ok
and 27.7.1.3,14 undefined behaviour when sp doesn't
come from a previous seekoff or seekpos stands in
the way. Anyway...

Tested x86-linux. Ok with you?

Paolo.

///////
2003-05-30  Paolo Carlini  <pcarlini@unitus.it>

	* include/bits/sstream.tcc (seekpos): Test against _M_out_lim
	not _M_out_end, since the former actually points to the string
	end (vs buffer end).
	* testsuite/27_io/basic_stringbuf/seekpos/char/3.cc: New.

diff -urN libstdc++-v3-1/include/bits/sstream.tcc libstdc++-v3/include/bits/sstream.tcc
--- libstdc++-v3-1/include/bits/sstream.tcc	2003-05-31 00:49:54.000000000 +0200
+++ libstdc++-v3/include/bits/sstream.tcc	2003-05-30 22:20:42.000000000 +0200
@@ -194,7 +194,7 @@
 	  if (__testout)
 	    {
 	      __beg = this->_M_out_beg;
-	      __end = this->_M_out_end;
+	      __end = this->_M_out_lim;
 	      if (0 <= __pos && __pos <= __end - __beg)
 		__testposo = true;
 	    }
diff -urN libstdc++-v3-1/testsuite/27_io/basic_stringbuf/seekpos/char/3.cc libstdc++-v3/testsuite/27_io/basic_stringbuf/seekpos/char/3.cc
--- libstdc++-v3-1/testsuite/27_io/basic_stringbuf/seekpos/char/3.cc	1970-01-01 01:00:00.000000000 +0100
+++ libstdc++-v3/testsuite/27_io/basic_stringbuf/seekpos/char/3.cc	2003-05-31 00:33:35.000000000 +0200
@@ -0,0 +1,47 @@
+// 2003-05-30  Paolo Carlini  <pcarlini@unitus.it>
+
+// Copyright (C) 2003 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 2, 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 COPYING.  If not, write to the Free
+// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
+// USA.
+
+#include <sstream>
+#include <testsuite_hooks.h>
+
+void test01() 
+{
+  bool 	test = true;
+  using namespace std;
+  typedef stringbuf::pos_type pos_type;
+  typedef stringbuf::off_type off_type;
+
+  stringbuf strb_01(ios_base::out);
+
+  strb_01.sputn("broken peak", 11);
+  pos_type pt_1 = strb_01.pubseekoff(0, ios_base::end, ios_base::out);
+  // In general, according to 27.7.1.3,14, the below has undefined
+  // behaviour since pt_1 + off_type(1) doesn't come from a
+  // previous pubseekpos or pubseekoff. However, given v3 implementation,
+  // this was useful to expose a bug in pubseekpos checks.
+  pos_type pt_2 = strb_01.pubseekpos(pt_1 + off_type(1), ios_base::out);
+  VERIFY( pt_2 == pos_type(off_type(-1)) );
+}
+
+int main()
+{
+  test01();
+  return 0;
+}