On Do, 2016-06-02 at 15:01 -0700, Paul Eggert wrote:
> On 06/02/2016 02:26 PM, David Seifert wrote:
> >
> > We could relax the whole thing a bit, and maybe just make a plain
> > __cplusplus check, without a version number. This keeps the C side
> > as
> > it always has been, but allows C++'s proper literals to kick in.
> >
> > In addition, _Bool is also a major obstacle, as it does not exist
> > in
> > C++ (and does so only for GCC due to some GNUisms in libstdc++ with
> > -std=c++98). Would you consider moving away from _Bool and
> > replacing
> > all uses of it with bool? After all, <stdbool.h> by itself only
> > mandates the existence of bool/true/false.
> Sure, that all sounds fine (in C++ only of course).
Dear Paul,
attached the patch. I believe this patch in fact increases strictness
even for C code, as it relies on the proper functioning of the "bool"
macro. I have tested it with multiple C and C++ compilers on OS X and
Linux:
OS X (current stdbool.m4):
CC = gcc-apple-4.2
checking for stdbool.h that conforms to C99... yes
checking for _Bool... yes
CC = gcc-mp-5
checking for stdbool.h that conforms to C99... yes
checking for _Bool... yes
CC = gcc-mp-6
checking for stdbool.h that conforms to C99... yes
checking for _Bool... yes
CC = clang-mp-3.7
checking for stdbool.h that conforms to C99... yes
checking for _Bool... yes
CC = g++-apple-4.2
checking for stdbool.h that conforms to C99... yes
checking for _Bool... no
CC = g++-mp-5
checking for stdbool.h that conforms to C99... yes
checking for _Bool... no
CC = g++-mp-6
checking for stdbool.h that conforms to C99... yes
checking for _Bool... no
CC = clang++-mp-3.7
checking for stdbool.h that conforms to C99... no
checking for _Bool... no
OS X (new stdbool.m4):
C = gcc-apple-4.2
checking for stdbool.h that conforms to C99... yes
checking for _Bool... yes
CC = gcc-mp-5
checking for stdbool.h that conforms to C99... yes
checking for _Bool... yes
CC = gcc-mp-6
checking for stdbool.h that conforms to C99... yes
checking for _Bool... yes
CC = clang-mp-3.7
checking for stdbool.h that conforms to C99... yes
checking for _Bool... yes
CC = g++-apple-4.2
checking for stdbool.h that conforms to C99... yes
checking for _Bool... no
CC = g++-mp-5
checking for stdbool.h that conforms to C99... yes
checking for _Bool... no
CC = g++-mp-6
checking for stdbool.h that conforms to C99... yes
checking for _Bool... no
CC = clang++-mp-3.7
checking for stdbool.h that conforms to C99... yes
checking for _Bool... no
Linux (current stdbool.m4):
CC = gcc-4.9.3
checking for stdbool.h that conforms to C99... yes
checking for _Bool... yes
CC = gcc-5.3.0
checking for stdbool.h that conforms to C99... yes
checking for _Bool... yes
CC = clang-3.8
checking for stdbool.h that conforms to C99... yes
checking for _Bool... yes
CC = g++-4.9.3
checking for stdbool.h that conforms to C99... yes
checking for _Bool... no
CC = g++-5.3.0
checking for stdbool.h that conforms to C99... yes
checking for _Bool... no
CC = clang++-3.8
checking for stdbool.h that conforms to C99... no
checking for _Bool... no
Linux (new stdbool.m4):
CC = gcc-4.9.3
checking for stdbool.h that conforms to C99... yes
checking for _Bool... yes
CC = gcc-5.3.0
checking for stdbool.h that conforms to C99... yes
checking for _Bool... yes
CC = clang-3.8
checking for stdbool.h that conforms to C99... yes
checking for _Bool... yes
CC = g++-4.9.3
checking for stdbool.h that conforms to C99... yes
checking for _Bool... no
CC = g++-5.3.0
checking for stdbool.h that conforms to C99... yes
checking for _Bool... no
CC = clang++-3.8
checking for stdbool.h that conforms to C99... yes
checking for _Bool... no
As you can see, it works for Clang++ now too.
Regards
David
From d89f715f1a9e967a0ba246a5c226b51a76035f5c Mon Sep 17 00:00:00 2001
From: David Seifert <s...@gentoo.org>
Date: Fri, 3 Jun 2016 21:35:20 +0200
Subject: [PATCH] Make stdbool.m4 as compatible as possible for C++
---
m4/stdbool.m4 | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/m4/stdbool.m4 b/m4/stdbool.m4
index a556153..463092e 100644
--- a/m4/stdbool.m4
+++ b/m4/stdbool.m4
@@ -44,7 +44,7 @@ AC_DEFUN([AC_CHECK_HEADER_STDBOOL],
[[
#include <stdbool.h>
- #if __cplusplus < 201103
+ #ifndef __cplusplus
#ifndef bool
"error: bool is not defined"
#endif
@@ -66,29 +66,29 @@ AC_DEFUN([AC_CHECK_HEADER_STDBOOL],
"error: __bool_true_false_are_defined is not defined"
#endif
- struct s { _Bool s: 1; _Bool t; } s;
+ struct s { bool s: 1; bool t; } s;
char a[true == 1 ? 1 : -1];
char b[false == 0 ? 1 : -1];
char c[__bool_true_false_are_defined == 1 ? 1 : -1];
char d[(bool) 0.5 == true ? 1 : -1];
/* See body of main program for 'e'. */
- char f[(_Bool) 0.0 == false ? 1 : -1];
+ char f[(bool) 0.0 == false ? 1 : -1];
char g[true];
- char h[sizeof (_Bool)];
+ char h[sizeof (bool)];
char i[sizeof s.t];
enum { j = false, k = true, l = false * true, m = true * 256 };
/* The following fails for
HP aC++/ANSI C B3910B A.05.55 [Dec 04 2003]. */
- _Bool n[m];
+ bool n[m];
char o[sizeof n == m * sizeof n[0] ? 1 : -1];
- char p[-1 - (_Bool) 0 < 0 && -1 - (bool) 0 < 0 ? 1 : -1];
+ char p[-1 - (bool) 0 < 0 && -1 - (bool) 0 < 0 ? 1 : -1];
/* Catch a bug in an HP-UX C compiler. See
http://gcc.gnu.org/ml/gcc-patches/2003-12/msg02303.html
http://lists.gnu.org/archive/html/bug-coreutils/2005-11/msg00161.html
*/
- _Bool q = true;
- _Bool *pq = &q;
+ bool q = true;
+ bool *pq = &q;
]],
[[
bool e = &s;
--
2.8.3
