stdbool.h: Update true and false expansions for C2x

C2x has changed the expansions of the true and false macros in
<stdbool.h> so that they have type _Bool (including in #if conditions,
i.e. an unsigned type in that context).  Use the new expansions in
GCC's <stdbool.h> for C2x.

See bug 82272 for related discussion (but this patch does *not*
implement the warning discussed there).

Note that it's possible there may be a further change to make bool,
true and false keywords (there was support in principle for that at
the April WG14 meeting).  But currently these expansions of type _Bool
are what C2x requires and there isn't actually a paper before WG14 at
present that would introduce the new keywords.

Bootstrapped with no regressions on x86_64-pc-linux-gnu.  OK to
commit?

gcc/
2020-10-28  Joseph Myers  <joseph@codesourcery.com>

	* ginclude/stdbool.c [__STDC_VERSION__ > 201710L] (true, false):
	Define with type _Bool.

gcc/testsuite/
2020-10-28  Joseph Myers  <joseph@codesourcery.com>

	* gcc.dg/c11-bool-1.c, gcc.dg/c2x-bool-1.c, gcc.dg/c99-bool-4.c:
	New tests.

On Thu, Oct 29, 2020 at 12:26 AM Joseph Myers <joseph@codesourcery.com> wrote:
>
> C2x has changed the expansions of the true and false macros in
> <stdbool.h> so that they have type _Bool (including in #if conditions,
> i.e. an unsigned type in that context).  Use the new expansions in
> GCC's <stdbool.h> for C2x.
>
> See bug 82272 for related discussion (but this patch does *not*
> implement the warning discussed there).
>
> Note that it's possible there may be a further change to make bool,
> true and false keywords (there was support in principle for that at
> the April WG14 meeting).  But currently these expansions of type _Bool
> are what C2x requires and there isn't actually a paper before WG14 at
> present that would introduce the new keywords.
>
> Bootstrapped with no regressions on x86_64-pc-linux-gnu.  OK to
> commit?

OK

> gcc/
> 2020-10-28  Joseph Myers  <joseph@codesourcery.com>
>
>         * ginclude/stdbool.c [__STDC_VERSION__ > 201710L] (true, false):
>         Define with type _Bool.
>
> gcc/testsuite/
> 2020-10-28  Joseph Myers  <joseph@codesourcery.com>
>
>         * gcc.dg/c11-bool-1.c, gcc.dg/c2x-bool-1.c, gcc.dg/c99-bool-4.c:
>         New tests.
>
> diff --git a/gcc/ginclude/stdbool.h b/gcc/ginclude/stdbool.h
> index 1b56498d96f..23554223d67 100644
> --- a/gcc/ginclude/stdbool.h
> +++ b/gcc/ginclude/stdbool.h
> @@ -31,8 +31,13 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
>  #ifndef __cplusplus
>
>  #define bool   _Bool
> +#if defined __STDC_VERSION__ && __STDC_VERSION__ > 201710L
> +#define true   ((_Bool)+1u)
> +#define false  ((_Bool)+0u)
> +#else
>  #define true   1
>  #define false  0
> +#endif
>
>  #else /* __cplusplus */
>
> diff --git a/gcc/testsuite/gcc.dg/c11-bool-1.c b/gcc/testsuite/gcc.dg/c11-bool-1.c
> new file mode 100644
> index 00000000000..0412624a706
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/c11-bool-1.c
> @@ -0,0 +1,50 @@
> +/* Test macro expansions in <stdbool.h> in C11.  */
> +/* { dg-do run } */
> +/* { dg-options "-std=c11 -pedantic-errors" } */
> +
> +#include <stdbool.h>
> +
> +#define str(x) xstr(x)
> +#define xstr(x) #x
> +
> +extern void abort (void);
> +extern void exit (int);
> +extern int strcmp (const char *, const char *);
> +
> +#if false - 1 >= 0
> +#error "false unsigned in #if"
> +#endif
> +
> +#if false != 0
> +#error "false not 0 in #if"
> +#endif
> +
> +#if true - 2 >= 0
> +#error "true unsigned in #if"
> +#endif
> +
> +#if true != 1
> +#error "true not 1 in #if"
> +#endif
> +
> +int
> +main (void)
> +{
> +  if (strcmp (str (bool), "_Bool") != 0)
> +    abort ();
> +  if (_Generic (true, int : 1) != 1)
> +    abort ();
> +  if (true != 1)
> +    abort ();
> +  if (strcmp (str (true), "1") != 0)
> +    abort ();
> +  if (_Generic (false, int : 1) != 1)
> +    abort ();
> +  if (false != 0)
> +    abort ();
> +  if (strcmp (str (false), "0") != 0)
> +    abort ();
> +  if (strcmp (str (__bool_true_false_are_defined), "1") != 0)
> +    abort ();
> +  exit (0);
> +}
> diff --git a/gcc/testsuite/gcc.dg/c2x-bool-1.c b/gcc/testsuite/gcc.dg/c2x-bool-1.c
> new file mode 100644
> index 00000000000..b64da1f7b43
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/c2x-bool-1.c
> @@ -0,0 +1,50 @@
> +/* Test macro expansions in <stdbool.h> in C2x.  */
> +/* { dg-do run } */
> +/* { dg-options "-std=c2x -pedantic-errors" } */
> +
> +#include <stdbool.h>
> +
> +#define str(x) xstr(x)
> +#define xstr(x) #x
> +
> +extern void abort (void);
> +extern void exit (int);
> +extern int strcmp (const char *, const char *);
> +
> +#if false - 1 < 0
> +#error "false signed in #if"
> +#endif
> +
> +#if false != 0
> +#error "false not 0 in #if"
> +#endif
> +
> +#if true - 2 < 0
> +#error "true signed in #if"
> +#endif
> +
> +#if true != 1
> +#error "true not 1 in #if"
> +#endif
> +
> +int
> +main (void)
> +{
> +  if (strcmp (str (bool), "_Bool") != 0)
> +    abort ();
> +  if (_Generic (true, _Bool : 1) != 1)
> +    abort ();
> +  if (true != 1)
> +    abort ();
> +  if (strcmp (str (true), "((_Bool)+1u)") != 0)
> +    abort ();
> +  if (_Generic (false, _Bool : 1) != 1)
> +    abort ();
> +  if (false != 0)
> +    abort ();
> +  if (strcmp (str (false), "((_Bool)+0u)") != 0)
> +    abort ();
> +  if (strcmp (str (__bool_true_false_are_defined), "1") != 0)
> +    abort ();
> +  exit (0);
> +}
> diff --git a/gcc/testsuite/gcc.dg/c99-bool-4.c b/gcc/testsuite/gcc.dg/c99-bool-4.c
> new file mode 100644
> index 00000000000..5cae18ad0ce
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/c99-bool-4.c
> @@ -0,0 +1,46 @@
> +/* Test macro expansions in <stdbool.h> in C99.  */
> +/* { dg-do run } */
> +/* { dg-options "-std=c99 -pedantic-errors" } */
> +
> +#include <stdbool.h>
> +
> +#define str(x) xstr(x)
> +#define xstr(x) #x
> +
> +extern void abort (void);
> +extern void exit (int);
> +extern int strcmp (const char *, const char *);
> +
> +#if false - 1 >= 0
> +#error "false unsigned in #if"
> +#endif
> +
> +#if false != 0
> +#error "false not 0 in #if"
> +#endif
> +
> +#if true - 2 >= 0
> +#error "true unsigned in #if"
> +#endif
> +
> +#if true != 1
> +#error "true not 1 in #if"
> +#endif
> +
> +int
> +main (void)
> +{
> +  if (strcmp (str (bool), "_Bool") != 0)
> +    abort ();
> +  if (true != 1)
> +    abort ();
> +  if (strcmp (str (true), "1") != 0)
> +    abort ();
> +  if (false != 0)
> +    abort ();
> +  if (strcmp (str (false), "0") != 0)
> +    abort ();
> +  if (strcmp (str (__bool_true_false_are_defined), "1") != 0)
> +    abort ();
> +  exit (0);
> +}
>
> --
> Joseph S. Myers
> joseph@codesourcery.com