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Re: Problem with stdbool.h redefining true/false even in C++
From: |
Paul Eggert |
Subject: |
Re: Problem with stdbool.h redefining true/false even in C++ |
Date: |
Wed, 29 Aug 2012 07:59:43 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux i686; rv:14.0) Gecko/20120714 Thunderbird/14.0 |
I'm no C++ expert but this one looks like there's a straightforward
fix: just use C++'s bool if available. That's what GCC's stdbool.h does,
anyway. With other compilers this may be an issue of C and C++
disagree with how _Bool is implemented but I suppose we can burn
those bridges when we come to them.
Here's the patch I installed into gnulib.
Please give it a try, and further patches are welcome.
>From 067dea8fdc99b30a826c0c8aff8060fe4f8095bf Mon Sep 17 00:00:00 2001
From: Paul Eggert <address@hidden>
Date: Wed, 29 Aug 2012 07:52:32 -0700
Subject: [PATCH] stdbool: be more compatible with mixed C/C++ compiles
* lib/stdbool.in.h (_Bool, true, false) [__cplusplus]:
Define to bool, true, false, respectively, as GCC's builtin
stdbool.h does. Problem reported by Michael Goffioul in
<http://lists.gnu.org/archive/html/bug-gnulib/2012-08/msg00143.html>.
---
ChangeLog | 8 ++++++++
lib/stdbool.in.h | 48 +++++++++++++++++++++++++++++-------------------
2 files changed, 37 insertions(+), 19 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 63f651f..f484d28 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2012-08-29 Paul Eggert <address@hidden>
+
+ stdbool: be more compatible with mixed C/C++ compiles
+ * lib/stdbool.in.h (_Bool, true, false) [__cplusplus]:
+ Define to bool, true, false, respectively, as GCC's builtin
+ stdbool.h does. Problem reported by Michael Goffioul in
+ <http://lists.gnu.org/archive/html/bug-gnulib/2012-08/msg00143.html>.
+
2012-08-28 Jim Meyering <address@hidden>
revert last change: it was not needed
diff --git a/lib/stdbool.in.h b/lib/stdbool.in.h
index e58f211..924c8ff 100644
--- a/lib/stdbool.in.h
+++ b/lib/stdbool.in.h
@@ -66,24 +66,18 @@
# undef true
#endif
-/* For the sake of symbolic names in gdb, we define true and false as
- enum constants, not only as macros.
- It is tempting to write
- typedef enum { false = 0, true = 1 } _Bool;
- so that gdb prints values of type 'bool' symbolically. But if we do
- this, values of type '_Bool' may promote to 'int' or 'unsigned int'
- (see ISO C 99 6.7.2.2.(4)); however, '_Bool' must promote to 'int'
- (see ISO C 99 6.3.1.1.(2)). So we add a negative value to the
- enum; this ensures that '_Bool' promotes to 'int'. */
-#if defined __cplusplus || (defined __BEOS__ && !defined __HAIKU__)
+#ifdef __cplusplus
+# define _Bool bool
+#else
+# if defined __BEOS__ && !defined __HAIKU__
/* A compiler known to have 'bool'. */
/* If the compiler already has both 'bool' and '_Bool', we can assume they
are the same types. */
-# if address@hidden@
+# if address@hidden@
typedef bool _Bool;
-# endif
-#else
-# if !defined __GNUC__
+# endif
+# else
+# if !defined __GNUC__
/* If @HAVE__BOOL@:
Some HP-UX cc and AIX IBM C compiler versions have compiler bugs when
the built-in _Bool type is used. See
@@ -103,19 +97,35 @@ typedef bool _Bool;
"Invalid enumerator. (badenum)" with HP-UX cc on Tru64.
The only benefit of the enum, debuggability, is not important
with these compilers. So use 'signed char' and no enum. */
-# define _Bool signed char
-# else
+# define _Bool signed char
+# else
/* With this compiler, trust the _Bool type if the compiler has it. */
-# if address@hidden@
+# if address@hidden@
+ /* For the sake of symbolic names in gdb, define true and false as
+ enum constants, not only as macros.
+ It is tempting to write
+ typedef enum { false = 0, true = 1 } _Bool;
+ so that gdb prints values of type 'bool' symbolically. But then
+ values of type '_Bool' might promote to 'int' or 'unsigned int'
+ (see ISO C 99 6.7.2.2.(4)); however, '_Bool' must promote to 'int'
+ (see ISO C 99 6.3.1.1.(2)). So add a negative value to the
+ enum; this ensures that '_Bool' promotes to 'int'. */
typedef enum { _Bool_must_promote_to_int = -1, false = 0, true = 1 } _Bool;
+# endif
# endif
# endif
#endif
#define bool _Bool
/* The other macros must be usable in preprocessor directives. */
-#define false 0
-#define true 1
+#ifdef __cplusplus
+# define false false
+# define true true
+#else
+# define false 0
+# define true 1
+#endif
+
#define __bool_true_false_are_defined 1
#endif /* _GL_STDBOOL_H */
--
1.7.11.4
- Problem with stdbool.h redefining true/false even in C++, Michael Goffioul, 2012/08/29
- Re: Problem with stdbool.h redefining true/false even in C++,
Paul Eggert <=
- Re: Problem with stdbool.h redefining true/false even in C++, Michael Goffioul, 2012/08/29
- Re: Problem with stdbool.h redefining true/false even in C++, Michael Goffioul, 2012/08/29
- Re: Problem with stdbool.h redefining true/false even in C++, John W. Eaton, 2012/08/29
- Re: Problem with stdbool.h redefining true/false even in C++, John W. Eaton, 2012/08/29
- Re: Problem with stdbool.h redefining true/false even in C++, Paul Eggert, 2012/08/29
- Re: Problem with stdbool.h redefining true/false even in C++, Michael Goffioul, 2012/08/29
- Re: Problem with stdbool.h redefining true/false even in C++, Paul Eggert, 2012/08/29
- Re: Problem with stdbool.h redefining true/false even in C++, Michael Goffioul, 2012/08/29
- Re: Problem with stdbool.h redefining true/false even in C++, Paul Eggert, 2012/08/29
- Re: Problem with stdbool.h redefining true/false even in C++, John W. Eaton, 2012/08/29