Puzzled!

[Jakub Jelinek]

On Thu, Dec 05, 2002 at 01:26:55PM -0800, Roland McGrath wrote:
> >     * The macro |math_errhandling| is not defined in |math.h|
> 
> >From glibc/CONFORMANCE:
> 
> 	Implementing MATH_ERRNO, MATH_ERREXCEPT and math_errhandling in
> 	<math.h> needs compiler support: see
> 
> 	http://sources.redhat.com/ml/libc-hacker/2000-06/msg00008.html
> 	http://sources.redhat.com/ml/libc-hacker/2000-06/msg00014.html
> 	http://sources.redhat.com/ml/libc-hacker/2000-06/msg00015.html

What exactly is required on gcc side? Verifying that without -ffast-math
all float builtins on EDOM/ERANGE arguments either set errno, or bail to
library functions?

> >     * The |hh| specifier for |d|, |i|,|o|,|u|,|x|, or |X| conversion
> >       specifier does not convert the value to a |signed| or |unsigned|
> >       char before printing. This applies to both the wide and narrow
> >       versions of the input/output functions.
> 
> Yes it does.

Not for d or i.
#include <stdio.h>

int main (void)
{
  printf ("%hhd\n", -321);
  printf ("%hhu\n", 321);
  printf ("%hhd\n", -126);
  printf ("%hhu\n", -126);
  printf ("%hhd\n", 231);
  printf ("%hhu\n", 231);
  printf ("%hhd\n", 312);
  printf ("%hhu\n", 312);
}
gives:
-321
65
-126
130
231
231
312
56

But see Joseph's mail; for signed conversions I think there is no arguing
that it falls into implementation-defined area.

> >     * The |SCN| macros for unsigned integers that correspond to the |X|
> >       specifier for |fscanf| in |inttypes.h| are not implemented.
> 
> Are there supposed to be SCNX* in addition to SCNx*?

They are allowed, not required, but I don't see much value in defining SCNX*,
as it has the same behaviour as SCNx*.

ISO C99 7.8.1:
...
4    The fscanf macros for signed integers are:

            SCNdN           SCNdLEASTN               SCNdFASTN              SCNdMAX SCNdPTR
            SCNiN           SCNiLEASTN               SCNiFASTN              SCNiMAX SCNiPTR

5    The fscanf macros for unsigned integers are:

            SCNoN           SCNoLEASTN               SCNoFASTN              SCNoMAX SCNoPTR
            SCNuN           SCNuLEASTN               SCNuFASTN              SCNuMAX SCNuPTR
            SCNxN           SCNxLEASTN               SCNxFASTN              SCNxMAX SCNxPTR

...
     7.26.4  Format conversion of integer types <inttypes.h>

1    Macro names beginning with PRI or SCN followed by any lowercase letter or X may be
     added to the macros defined in the <inttypes.h> header.

	Jakub