I installed the attached patch into Gnulib, reflecting a patch I
recently installed into Autoconf
<https://git.savannah.gnu.org/cgit/autoconf.git/commit/?id=6dcecb780a69bd208088d666b299e92aa7ae7e80>.
I think we need a new Autoconf macro that obsoletes AC_HEADER_STDBOOL
and AC_CHECK_HEADER_STDBOOL. This new macro should arrange for 'bool',
'true' and 'false' to work, without programs having to include
stdbool.h. For C23 and C++ the new macro should do nothing. For C99
through C17 it should include <stdbool.h> in config.h. For pre-C99 it
should #define bool, true, and false in config.h.
Eventually Gnulib and other code can stop using AC_*HEADER_CHECKBOOL and
stop including <stdbool.h>.
I'm thinking of calling the new macro AC_C_BOOL. Gnulib can have a new
c-bool module that implements AC_C_BOOL for platforms running older
Autoconf.
Comments?
From f960bc91cd325cee7e1262944ca6114bfd4d1c1f Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@xxxxxxxxxxx>
Date: Sat, 13 Aug 2022 20:00:02 -0700
Subject: [PATCH] stdbool: port to C23
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
* m4/stdbool.m4 (AC_CHECK_HEADER_STDBOOL): Copy from bleeding-edge
Autoconf. Don’t define if Autoconf 2.72 or later.
* tests/test-stdbool.c (bool, false, true)
(__bool_true_false_are_defined): Do not require these to be
defined. C23 still requires __bool_true_false_are_defined but
marks it as obsolescent, and it’s no longer worth testing.
(WORKING_BOOL): New macro, which also tests __STDC_VERSION__.
Use it in tests for working bool.
Test for bool instead of for _Bool, which C23 says is obsolescent.
---
ChangeLog | 13 ++++++
m4/stdbool.m4 | 105 ++++++++++++++++++++++---------------------
tests/test-stdbool.c | 41 ++++++++---------
3 files changed, 84 insertions(+), 75 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index e0bf24fc90..eecf44ba01 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,16 @@
+2022-08-13 Paul Eggert <eggert@xxxxxxxxxxx>
+
+ stdbool: port to C23
+ * m4/stdbool.m4 (AC_CHECK_HEADER_STDBOOL): Copy from bleeding-edge
+ Autoconf. Don’t define if Autoconf 2.72 or later.
+ * tests/test-stdbool.c (bool, false, true)
+ (__bool_true_false_are_defined): Do not require these to be
+ defined. C23 still requires __bool_true_false_are_defined but
+ marks it as obsolescent, and it’s no longer worth testing.
+ (WORKING_BOOL): New macro, which also tests __STDC_VERSION__.
+ Use it in tests for working bool.
+ Test for bool instead of for _Bool, which C23 says is obsolescent.
+
2022-08-13 Bruno Haible <bruno@xxxxxxxxx>
gnulib-tool.py: Fix some code generation details.
diff --git a/m4/stdbool.m4 b/m4/stdbool.m4
index 3e6c400546..c67908aa87 100644
--- a/m4/stdbool.m4
+++ b/m4/stdbool.m4
@@ -43,75 +43,76 @@ AC_DEFUN([gl_STDBOOL_H],
AC_SUBST([HAVE__BOOL])
])
-# This version of the macro is needed in autoconf <= 2.68.
+m4_version_prereq([2.72], [], [
AC_DEFUN([AC_CHECK_HEADER_STDBOOL],
- [AC_CACHE_CHECK([for stdbool.h that conforms to C99],
+ [AC_CHECK_TYPES([_Bool])
+ AC_CACHE_CHECK([for stdbool.h that conforms to C99 or later],
[ac_cv_header_stdbool_h],
[AC_COMPILE_IFELSE(
[AC_LANG_PROGRAM(
- [[
- #include <stdbool.h>
-
- #ifdef __cplusplus
- typedef bool Bool;
- #else
- typedef _Bool Bool;
- #ifndef bool
- "error: bool is not defined"
- #endif
- #ifndef false
- "error: false is not defined"
- #endif
- #if false
- "error: false is not 0"
- #endif
- #ifndef true
- "error: true is not defined"
- #endif
- #if true != 1
- "error: true is not 1"
- #endif
+ [[#include <stdbool.h>
+
+ /* "true" and "false" should be usable in #if expressions and
+ integer constant expressions, and "bool" should be a valid
+ type name.
+
+ Although C 1999 requires bool, true, and false to be macros,
+ C 2023 and C++ 2011 overrule that, so do not test for that.
+ Although C 1999 requires __bool_true_false_are_defined and
+ _Bool, C 2023 says they are obsolescent, so do not require
+ them. */
+
+ #if !true
+ #error "'true' is not true"
+ #endif
+ #if true != 1
+ #error "'true' is not equal to 1"
#endif
+ char b[true == 1 ? 1 : -1];
+ char c[true];
- #ifndef __bool_true_false_are_defined
- "error: __bool_true_false_are_defined is not defined"
+ #if false
+ #error "'false' is not false"
+ #endif
+ #if false != 0
+ #error "'false' is not equal to 0"
#endif
+ char d[false == 0 ? 1 : -1];
+
+ enum { e = false, f = true, g = false * true, h = true * 256 };
+
+ char i[(bool) 0.5 == true ? 1 : -1];
+ char j[(bool) 0.0 == false ? 1 : -1];
+ char k[sizeof (bool) > 0 ? 1 : -1];
+
+ struct sb { bool s: 1; bool t; } s;
+ char l[sizeof s.t > 0 ? 1 : -1];
- struct s { Bool s: 1; Bool t; bool u: 1; bool v; } 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 g[true];
- 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];
- char o[sizeof n == m * sizeof n[0] ? 1 : -1];
- char p[-1 - (Bool) 0 < 0 && -1 - (bool) 0 < 0 ? 1 : -1];
+ bool m[h];
+ char n[sizeof m == h * sizeof m[0] ? 1 : -1];
+ char o[-1 - (bool) 0 < 0 ? 1 : -1];
/* Catch a bug in an HP-UX C compiler. See
https://gcc.gnu.org/ml/gcc-patches/2003-12/msg02303.html
https://lists.gnu.org/r/bug-coreutils/2005-11/msg00161.html
*/
- Bool q = true;
- Bool *pq = &q;
- bool *qq = &q;
+ bool p = true;
+ bool *pp = &p;
]],
[[
- bool e = &s;
- *pq |= q; *pq |= ! q;
- *qq |= q; *qq |= ! q;
- /* Refer to every declared value, to avoid compiler optimizations. */
- return (!a + !b + !c + !d + !e + !f + !g + !h + !i + !!j + !k + !!l
- + !m + !n + !o + !p + !q + !pq + !qq);
+ bool ps = &s;
+ *pp |= p;
+ *pp |= ! p;
+
+ /* Refer to every declared value, so they cannot be
+ discarded as unused. */
+ return (!a + !b + !c + !d + !e + !f + !g + !h + !i + !j + !k
+ + !l + !m + !n + !o + !p + !pp + !ps);
]])],
[ac_cv_header_stdbool_h=yes],
[ac_cv_header_stdbool_h=no])])
- AC_CHECK_TYPES([_Bool])
-])
+])# AC_CHECK_HEADER_STDBOOL
+
+]) # m4_version_prereq 2.72
diff --git a/tests/test-stdbool.c b/tests/test-stdbool.c
index 3574a9e72f..27fd16d010 100644
--- a/tests/test-stdbool.c
+++ b/tests/test-stdbool.c
@@ -35,35 +35,30 @@
#include <stdbool.h>
-#ifndef bool
- "error: bool is not defined"
-#endif
-#ifndef false
- "error: false is not defined"
-#endif
#if false
"error: false is not 0"
#endif
-#ifndef true
- "error: true is not defined"
-#endif
#if true != 1
"error: true is not 1"
#endif
-#ifndef __bool_true_false_are_defined
- "error: __bool_true_false_are_defined is not defined"
-#endif
/* Several tests cannot be guaranteed with gnulib's <stdbool.h>, at
least, not for all compilers and compiler options. */
-#if HAVE_STDBOOL_H || 3 <= __GNUC__ || 4 <= __clang_major__
-struct s { _Bool s: 1; _Bool t; } s;
+#if (202311 <= __STDC_VERSION__ || defined __cplusplus \
+ || HAVE_STDBOOL_H || 3 <= __GNUC__ || 4 <= __clang_major__)
+# define WORKING_BOOL 1
+#else
+# define WORKING_BOOL 0
+#endif
+
+#if WORKING_BOOL
+struct s { bool s: 1; bool t; } s;
#endif
char a[true == 1 ? 1 : -1];
char b[false == 0 ? 1 : -1];
char c[__bool_true_false_are_defined == 1 ? 1 : -1];
-#if HAVE_STDBOOL_H || 3 <= __GNUC__ || 4 <= __clang_major__ /* See above. */
+#if WORKING_BOOL
char d[(bool) 0.5 == true ? 1 : -1];
# ifdef ADDRESS_CHECK_OKAY /* Avoid gcc warning. */
/* C99 may plausibly be interpreted as not requiring support for a cast from
@@ -73,30 +68,30 @@ char d[(bool) 0.5 == true ? 1 : -1];
bool e = &s;
# endif
# endif
-char f[(_Bool) 0.0 == false ? 1 : -1];
+char f[(bool) 0.0 == false ? 1 : -1];
#endif
char g[true];
-char h[sizeof (_Bool)];
-#if HAVE_STDBOOL_H || 3 <= __GNUC__ || 4 <= __clang_major__ /* See above. */
+char h[sizeof (bool)];
+#if WORKING_BOOL
char i[sizeof s.t];
#endif
enum { j = false, k = true, l = false * true, m = true * 256 };
-_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
https://gcc.gnu.org/ml/gcc-patches/2003-12/msg02303.html
https://lists.gnu.org/r/bug-coreutils/2005-11/msg00161.html
*/
-_Bool q = true;
-_Bool *pq = &q;
+bool q = true;
+bool *pq = &q;
int
main ()
{
int error = 0;
-#if HAVE_STDBOOL_H || 3 <= __GNUC_ || 4 <= __clang_major___ /* See above. */
+#if WORKING_BOOL
# ifdef ADDRESS_CHECK_OKAY /* Avoid gcc warning. */
/* A cast from a variable's address to bool is valid in expressions. */
{
--
2.34.1
