AC_CHECK_FUNCS difference between 2.54 and 2.56

[Albert Chin]

There seem to be problems with AC_CHECK_FUNCS on AIX with the IBM C
compiler (5.0.2.6). With autoconf 2.54, AC_CHECK_FUNCS(chflags)
outputs (b.c):
  ...
/* We use char because int might match the return type of a gcc2
   builtin and then its argument prototype would still apply.  */
char $ac_func ();
char (*f) ();

int
main ()
{
/* The GNU C library defines this for functions which it implements
    to always fail with ENOSYS.  Some functions are actually named
    something starting with __ and the normal name is an alias.  */
#if defined (__stub_$ac_func) || defined (__stub___$ac_func)
choke me
#else
f = $ac_func;
#endif

  ;
  return 0;
}
_ACEOF
  ...

Autoconf 2.56 outputs (c.c):
  ...
/* We use char because int might match the return type of a gcc2
   builtin and then its argument prototype would still apply.  */
char $ac_func ();
/* The GNU C library defines this for functions which it implements
    to always fail with ENOSYS.  Some functions are actually named
    something starting with __ and the normal name is an alias.  */
#if defined (__stub_$ac_func) || defined (__stub___$ac_func)
choke me
#else
char (*f) () = $ac_func;
#endif
#ifdef __cplusplus
}
#endif

int
main ()
{

  ;
  return 0;
}
_ACEOF

The problem is that chflags doesn't exist on AIX yet the test passes
because the IBM linker seems to optimize the call out:
  $ xlc -v b.c
  exec: 
/usr/vac/exe/xlcentry(xlcentry,-D_AIX,-D_AIX32,-D_AIX41,-D_AIX43,-D_IBMR2,-D_POWER,-qansialias,-ob.o,b.c,/tmp/xlcW01ctrMa,/tmp/xlcW11ctrMb,/dev/null,b.lst,c,/tmp/xlcW21ctrMc,NULL)
 
  exec: 
/usr/vac/exe/xlCcode(xlCcode,-qansialias,/tmp/xlcW01ctrMa,/tmp/xlcW11ctrMb,b.o,b.lst,/tmp/xlcW21ctrMc,NULL)
 
  exec: /bin/ld(ld,/lib/crt0.o,-bpT:0x10000000,-bpD:0x20000000,b.o,-lc,NULL) 
  unlink: b.o
  unlink: /tmp/xlcW01ctrMa
  unlink: /tmp/xlcW11ctrMb
  unlink: /tmp/xlcW21ctrMc

  $ xlc -v c.c
  exec: 
/usr/vac/exe/xlcentry(xlcentry,-D_AIX,-D_AIX32,-D_AIX41,-D_AIX43,-D_IBMR2,-D_POWER,-qansialias,-oc.o,c.c,/tmp/xlcW0Xytrya,/tmp/xlcW1Xytryb,/dev/null,c.lst,b,/tmp/xlcW2Xytryc,NULL)
 
  exec: 
/usr/vac/exe/xlCcode(xlCcode,-qansialias,/tmp/xlcW0Xytrya,/tmp/xlcW1Xytryb,c.o,c.lst,/tmp/xlcW2Xytryc,NULL)
 
  exec: /bin/ld(ld,/lib/crt0.o,-bpT:0x10000000,-bpD:0x20000000,c.o,-lc,NULL) 
  ld: 0711-317 ERROR: Undefined symbol: chflags
  ld: 0711-345 Use the -bloadmap or -bnoquiet option to obtain more information.
  unlink: /tmp/xlcW0Xytrya
  unlink: /tmp/xlcW1Xytryb
  unlink: /tmp/xlcW2Xytryc

So, can we go back to 2.54 behaviour?

-- 
albert chin (address@hidden)