compiling newlib

[Christophe MONAT]

Paul,

+ #include <errno.h>
probably would have avoided the trouble to add newlib-specific code.

It looks also that errno differs between glibc and newlib.

>From my memory glibc has a quite thorough libm test suite checking among other things the edge cases, I don't know what exist in this domain for newlib.

Regards,
--C


-----Original Message-----
From: Newlib <newlib-bounces@sourceware.org> On Behalf Of Paul Zimmermann
Sent: Tuesday, August 25, 2020 8:42 AM
To: Jeff Johnston <jjohnstn@redhat.com>
Cc: newlib@sourceware.org
Subject: Re: compiling newlib

thank you Jeff for your answer.

In return I found I believe an issue with newlib's tgammaf function, for input -0, where it gives +inf instead of -inf:

$ cat e.c
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#ifdef NEWLIB
/* without this, newlib says: undefined reference to `__errno' */ int errno;
int* __errno () { return &errno; }
#endif

int
main (int argc, char *argv[])
{
  float x = -0.0;
  float y = tgammaf (x);
  printf ("x=%.9e y=%.9e\n", x, y);
  return 0;
}

With glibc :

$ gcc e.c -lm
$ ./a.out
x=-0.000000000e+00 y=-inf

With NEWLIB :

$ gcc -DNEWLIB e.c /localdisk/zimmerma/newlib/libm/libm.a
$ ./a.out
x=-0.000000000e+00 y=inf

Best regards,
Paul