Patchwork <stdbool.h> should not define bool, true or false as macros for C++

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Submitter Jonathan Wakely
Date Jan. 9, 2012, 8:48 a.m.
Message ID <CAH6eHdQ4xWLYJEfYJ2ha-uebqGYZtWEsQkuFWQbp=eYFqDXQaA@mail.gmail.com>
Download mbox | patch
Permalink /patch/134973/
State New
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Comments

Jonathan Wakely - Jan. 9, 2012, 8:48 a.m.
GCC's implementation of <stdbool.h> is not valid for C++11 because
[support.runtime] p8 says "The header <cstdbool> and the header
<stdbool.h> shall not define macros named bool, true, or false."

This patch adds a libstdc++ test for that requirement and adjusts
stdbool.h to meet it.  I've left _Bool defined in C++ as a GNU
extension.

It's conceivable someone is relying on these macros being defined in
C++, in which case we could only define them when __cplusplus <
201103L, but IMHO it's better to not define them at all.

Tested x86_64-linux, OK for trunk?

gcc/
        * ginclude/stdbool.h (true, false, bool): Do not define for C++.

libstdc++/
        * testsuite/18_support/headers/cstdbool/macros.cc: New.
Jonathan Wakely - Jan. 9, 2012, 10:02 a.m.
I've just seen Richard's status email, so I guess this should wait for 4.8


On 9 January 2012 08:48, Jonathan Wakely wrote:
> GCC's implementation of <stdbool.h> is not valid for C++11 because
> [support.runtime] p8 says "The header <cstdbool> and the header
> <stdbool.h> shall not define macros named bool, true, or false."
>
> This patch adds a libstdc++ test for that requirement and adjusts
> stdbool.h to meet it.  I've left _Bool defined in C++ as a GNU
> extension.
>
> It's conceivable someone is relying on these macros being defined in
> C++, in which case we could only define them when __cplusplus <
> 201103L, but IMHO it's better to not define them at all.
>
> Tested x86_64-linux, OK for trunk?
>
> gcc/
>        * ginclude/stdbool.h (true, false, bool): Do not define for C++.
>
> libstdc++/
>        * testsuite/18_support/headers/cstdbool/macros.cc: New.
Gerald Pfeifer - Feb. 4, 2012, 11:35 p.m.
For what it's worth, I strongly suggest that you only define those when 
__cpluplus is pre-C++11.

There is simply too much software out there which will run into this
and being aggressive in breaking (admittedly non-standard confirming
programs) gives GCC a bad reputation and is not nice to our users to
begin with.

Gerald

On Mon, 9 Jan 2012, Jonathan Wakely wrote:
> I've just seen Richard's status email, so I guess this should wait for 4.8
> 
> 
> On 9 January 2012 08:48, Jonathan Wakely wrote:
>> GCC's implementation of <stdbool.h> is not valid for C++11 because
>> [support.runtime] p8 says "The header <cstdbool> and the header
>> <stdbool.h> shall not define macros named bool, true, or false."
>>
>> This patch adds a libstdc++ test for that requirement and adjusts
>> stdbool.h to meet it.  I've left _Bool defined in C++ as a GNU
>> extension.
>>
>> It's conceivable someone is relying on these macros being defined in
>> C++, in which case we could only define them when __cplusplus <
>> 201103L, but IMHO it's better to not define them at all.
>>
>> Tested x86_64-linux, OK for trunk?
>>
>> gcc/
>>        * ginclude/stdbool.h (true, false, bool): Do not define for C++.
>>
>> libstdc++/
>>        * testsuite/18_support/headers/cstdbool/macros.cc: New.

Patch

--- a/gcc/ginclude/stdbool.h
+++ b/gcc/ginclude/stdbool.h
@@ -1,4 +1,4 @@ 
-/* Copyright (C) 1998, 1999, 2000, 2009 Free Software Foundation, Inc.
+/* Copyright (C) 1998, 1999, 2000, 2009, 2012 Free Software Foundation, Inc.
 
 This file is part of GCC.
 
@@ -36,11 +36,8 @@  see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 
 #else /* __cplusplus */
 
-/* Supporting <stdbool.h> in C++ is a GCC extension.  */
+/* Supporting _Bool in C++ is a GCC extension.  */
 #define _Bool	bool
-#define bool	bool
-#define false	false
-#define true	true
 
 #endif /* __cplusplus */
 
--- /dev/null
+++ b/libstdc++-v3/testsuite/18_support/headers/cstdbool/macros.cc
@@ -0,0 +1,38 @@ 
+// { dg-do compile }
+// { dg-options "-std=gnu++11" }
+
+// Copyright (C) 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
+// 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/>.
+
+#include <cstdbool>
+
+#ifndef __bool_true_false_are_defined
+# error "The header <cstdbool> fails to define a macro named __bool_true_false_are_defined"
+#endif
+
+#ifdef bool
+# error "The header <cstdbool> defines a macro named bool"
+#endif
+
+#ifdef true
+# error "The header <cstdbool> defines a macro named true"
+#endif
+
+#ifdef false
+# error "The header <cstdbool> defines a macro named false"
+#endif
+