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Disentangle HAVE__BOOL from ac_cv_header_stdbool_h.

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AC_CHECK_HEADER_STDBOOL is documented to make two checks: whether the
C99 header <stdbool.h> is available and fulfills its
specification (i.e. including it makes the type ‘bool’ and the
constants ‘true’ and ‘false’ available), and, independently, whether
the type ‘_Bool’ is available.

In C++, the type ‘_Bool’ is usually _not_ available, but <stdbool.h>
is still supposed to be include-able and the type ‘bool’ and the
constants ‘true’ and ‘false’ are still supposed to be available
(unconditionally).  However, the test for <stdbool.h> fulfilling its
specification freely used _Bool, and would therefore fail spuriously.
Correct this by checking for _Bool first, and then refactoring the
test program for <stdbool.h> so that it does all its tests using bool,
then repeats them with _Bool only when available.

* lib/autoconf/headers.m4 (AC_CHECK_HEADER_STDBOOL): Do the test for
  _Bool before the test for stdbool.h.  Test semantics of bool
  unconditionally; test _Bool only when HAVE__BOOL is defined.
This commit is contained in:
Zack Weinberg 2020-11-28 11:08:28 -05:00
parent d81861ed01
commit 9886b7a922
No known key found for this signature in database
GPG Key ID: 384F8E68AC65B0D5
1 changed files with 91 additions and 47 deletions
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138
lib/autoconf/headers.m4
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@ -574,70 +574,114 @@ AN_IDENTIFIER([bool], [AC_CHECK_HEADER_STDBOOL])
AN_IDENTIFIER([true], [AC_CHECK_HEADER_STDBOOL])
AN_IDENTIFIER([false],[AC_CHECK_HEADER_STDBOOL])
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],
[ac_cv_header_stdbool_h],
[AC_COMPILE_IFELSE(
[AC_LANG_PROGRAM(
[[
#include <stdbool.h>
#if __cplusplus < 201103
#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
#endif
[[#include <stdbool.h>
#ifndef __bool_true_false_are_defined
"error: __bool_true_false_are_defined is not defined"
#error "__bool_true_false_are_defined is not defined"
#endif
char a[__bool_true_false_are_defined == 1 ? 1 : -1];
struct s { _Bool s: 1; _Bool t; } s;
/* Regardless of whether this is C++ or "_Bool" is a
valid type name, "true" and "false" should be usable
in #if expressions and integer constant expressions,
and "bool" should be a valid type name. */
#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];
#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];
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/archive/html/bug-coreutils/2005-11/msg00161.html
https://gcc.gnu.org/ml/gcc-patches/2003-12/msg02303.html
https://lists.gnu.org/archive/html/bug-coreutils/2005-11/msg00161.html
*/
_Bool q = true;
_Bool *pq = &q;
bool p = true;
bool *pp = &p;
/* C 1999 specifies that bool, true, and false are to be
macros, but C++ 2011 and later overrule this. */
#if __cplusplus < 201103
#ifndef bool
#error "bool is not defined"
#endif
#ifndef false
#error "false is not defined"
#endif
#ifndef true
#error "true is not defined"
#endif
#endif
/* If _Bool is available, repeat with it all the tests
above that used bool. */
#ifdef HAVE__BOOL
struct sB { _Bool s: 1; _Bool t; } t;
char q[(_Bool) 0.5 == true ? 1 : -1];
char r[(_Bool) 0.0 == false ? 1 : -1];
char u[sizeof (_Bool) > 0 ? 1 : -1];
char v[sizeof t.t > 0 ? 1 : -1];
_Bool w[h];
char x[sizeof m == h * sizeof m[0] ? 1 : -1];
char y[-1 - (_Bool) 0 < 0 ? 1 : -1];
_Bool z = true;
_Bool *pz = &p;
#endif
]],
[[
bool e = &s;
*pq |= q;
*pq |= ! 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);
bool ps = &s;
*pp |= p;
*pp |= ! p;
#ifdef HAVE__BOOL
_Bool pt = &t;
*pz |= z;
*pz |= ! z;
#endif
/* 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
#ifdef HAVE__BOOL
+ !q + !r + !u + !v + !w + !x + !y + !z + !pt
#endif
);
]])],
[ac_cv_header_stdbool_h=yes],
[ac_cv_header_stdbool_h=no])])
AC_CHECK_TYPES([_Bool])
])# AC_CHECK_HEADER_STDBOOL