[Bug fortran/47293] libquadmath: strtoflt128 - NAN not correctly read and C99 hex floating point format missing

["burnus at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47293

Tobias Burnus <burnus at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|libquadmath: strtoflt128 -  |libquadmath: strtoflt128 -
                   |C99 hex floating point      |NAN not correctly read and
                   |format missing              |C99 hex floating point
                   |                            |format missing

--- Comment #1 from Tobias Burnus <burnus at gcc dot gnu.org> 2011-01-14 15:36:52 UTC ---
Additional problem: The NAN string to float128 conversion does not seem to
work.

[The way NaN is printed by the float128->string conversion function is also a
bit odd, but it seems to work (with libgfortran).]

The program below prints:

+N.aN000000000000000000e+02
+7.82797652694030368547e-4942

The a similar Fortran program prints (value printed as hex):
     0        0        0 FFFF8000   -- for NaN (gfortran and ifort)
     0 C0000000     FFFF        0   -- for the "NaN" string (= 0.78280E-4941)

If one debugs gdtoa/strtodg.c, one sees that STRTOG_NaN is properly detected.
Thus, either the bits are wrong in strtodg -- or it is wrongly handled in
strtoflt128.

Example (strtoflt128 was called "quadmath_strtopQ" before renaming.)

#include <quadmath.h>
#include <stdlib.h>  /* For abort.  */
#include <stdio.h>   /* For printf.  */

int main ()
{
  __float128 r;
  char str[200];
  r = nanq(NULL);
  quadmath_dtoaq (str, sizeof (str), 20, r);
  printf("%s\n", str);

  r = 3.0q;
  /* quadmath_strtopQ ("NaN", NULL, &r); */
  r = strtoflt128 ("NaN", NULL);
  quadmath_dtoaq (str, sizeof (str), 20, r);
  printf("%s\n", str);

  if (!isnanq(r)) abort();
  return 0;
}