Broken isnan(3) and/or DQNAN on Tru64

[Ludovic Courtès]

Hello,

On `alphaev56-dec-osf5.1b', NaN handling seems to be deeply broken.
Consider this piece of code:

--8<---------------cut here---------------start------------->8---
#include <math.h>

extern unsigned int DQNAN[2];

int
main (int argc, char *argv[])
{
  return isnan (* (double *) DQNAN);
}
--8<---------------cut here---------------end--------------->8---

When compiled with GCC 4.0.2, it bails out with SIGFPE.

Guile's 1.8 series does not use Gnulib (the next release series will use
Gnulib), so it's been relying on these facilities, which are also used
in Octave.  I'm wondering whether it worked with older Tru64 versions.

I know Gnulib's `isnan' module re-implements isnan(3) following the IEEE
specs, but in your experience is there any way to get a working isnan(3)
on Tru64?  Or perhaps it's DQNAN that's broken?

Thanks in advance,
Ludo'.