re PR c++/52119 ([C++11] overflow in signed left shift isn't diagnosed)

2012-02-05  Jeffrey Yasskin  <jyasskin@gcc.gnu.org>
	    Paolo Carlini  <paolo.carlini@oracle.com>

	PR libstdc++/52119
	* include/std/limits (__glibcxx_min): Fix to avoid undefined behavior.

From-SVN: r183905

libstdc++-v3/ChangeLog

+2012-02-05  Jeffrey Yasskin  <jyasskin@gcc.gnu.org>
+	    Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR libstdc++/52119
+	* include/std/limits (__glibcxx_min): Fix to avoid undefined behavior.
+
 2012-02-03  Benjamin Kosnik  <bkoz@redhat.com>
 
 	PR libstdc++/49445
@@ -97,7 +103,7 @@
 	PR libstdc++/51795
 	* include/bits/random.h (linear_congruential_generator): Add
 	static_assert preventing instantiation for values of 'a' and 'm'
-	currently handled incorrectly but _Mod::__calc.
+	currently handled incorrectly by _Mod::__calc.
 	* include/bits/random.tcc (seed_seq::generate): Avoid unsafe
 	uses of _Mod::__calc.
 

libstdc++-v3/include/std/limits

 // The template and inlines for the numeric_limits classes. -*- C++ -*-
 
 // Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,
-// 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
+// 2008, 2009, 2010, 2011, 2012 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
@@ -129,7 +129,7 @@
 #define __glibcxx_signed(T)	((T)(-1) < 0)
 
 #define __glibcxx_min(T) \
-  (__glibcxx_signed (T) ? (T)1 << __glibcxx_digits (T) : (T)0)
+  (__glibcxx_signed (T) ? -__glibcxx_max (T) - 1 : (T)0)
 
 #define __glibcxx_max(T) \
   (__glibcxx_signed (T) ? \