20000320-1.c

this is a gcc file, you can download it and learn its usetility, for further detail please look at t

#if defined(__mips__) && defined(__sgi__)
#include <sys/fpu.h>
#endif /* defined(__mips__) && defined(__sgi__) */
#include <limits.h>
#if UINT_MAX != 4294967295u || (ULONG_LONG_MAX != 18446744073709551615ull && ULONG_MAX != 18446744073709551615ull)
int main(void) { exit (0); }
#else
#if ULONG_MAX != 18446744073709551615ull
typedef unsigned long long ull;
#else
typedef unsigned long ull;
#endif
typedef unsigned ul;

union fl {
  float	f;
  ul l;
} uf;
union dl {
  double d;
  ull ll;
} ud;

int failed = 0;

void c(ull d, ul f)
{
  ud.ll = d;
  uf.f = (float) ud.d;
  if (uf.l != f)
    {
      failed++;
    }
}

int main()
{
#if defined(__mips__) && defined(__sgi__)
  /* Many MIPS chips round denormalized floating point numbers to zero
     rather than follow the IEEE standard.  Change the rounding mode
     to correspond to the IEEE rounding mode that rounds numbers to
     the nearest representable mode, the most common IEEE rounding
     mode.  */
  set_fpc_csr(0);
#endif /* defined(__mips__) && defined(__sgi__) */

  if (sizeof (float) != sizeof (ul)
      || sizeof (double) != sizeof (ull))
    exit (0);
  
  c(0x3690000000000000ULL, 0x00000000U);
#if (defined __arm__ || defined __thumb__) && ! (defined __ARMEB__ || defined __VFP_FP__)
  /* The ARM always stores FP numbers in big-wordian format,
     even when running in little-byteian mode.  */
  c(0x0000000136900000ULL, 0x00000001U);
  c(0xffffffff369fffffULL, 0x00000001U);
  c(0x0000000036A00000ULL, 0x00000001U);
  c(0xffffffff36A7ffffULL, 0x00000001U);
  c(0x0000000036A80000ULL, 0x00000002U);
  c(0xffffffff36AfffffULL, 0x00000002U);
  c(0x0000000036b00000ULL, 0x00000002U);
  c(0x0000000136b00000ULL, 0x00000002U);
  
  c(0xdfffffff380fffffULL, 0x007fffffU);
  c(0xe0000000380fffffULL, 0x00800000U);
  c(0xe0000001380fffffULL, 0x00800000U);
  c(0xffffffff380fffffULL, 0x00800000U);
  c(0x0000000038100000ULL, 0x00800000U);
  c(0x0000000138100000ULL, 0x00800000U);
  c(0x1000000038100000ULL, 0x00800000U);
  c(0x1000000138100000ULL, 0x00800001U);
  c(0x2fffffff38100000ULL, 0x00800001U);
  c(0x3000000038100000ULL, 0x00800002U);
  c(0x5000000038100000ULL, 0x00800002U);
  c(0x5000000138100000ULL, 0x00800003U);
#else
  c(0x3690000000000001ULL, 0x00000001U);
  c(0x369fffffffffffffULL, 0x00000001U);
  c(0x36A0000000000000ULL, 0x00000001U);
  c(0x36A7ffffffffffffULL, 0x00000001U);
  c(0x36A8000000000000ULL, 0x00000002U);
  c(0x36AfffffffffffffULL, 0x00000002U);
  c(0x36b0000000000000ULL, 0x00000002U);
  c(0x36b0000000000001ULL, 0x00000002U);
  
  c(0x380fffffdfffffffULL, 0x007fffffU);
  c(0x380fffffe0000000ULL, 0x00800000U);
  c(0x380fffffe0000001ULL, 0x00800000U);
  c(0x380fffffffffffffULL, 0x00800000U);
  c(0x3810000000000000ULL, 0x00800000U);
  c(0x3810000000000001ULL, 0x00800000U);
  c(0x3810000010000000ULL, 0x00800000U);
  c(0x3810000010000001ULL, 0x00800001U);
  c(0x381000002fffffffULL, 0x00800001U);
  c(0x3810000030000000ULL, 0x00800002U);
  c(0x3810000050000000ULL, 0x00800002U);
  c(0x3810000050000001ULL, 0x00800003U);
#endif

  if (failed)
    abort ();
  else
    exit (0);
}
#endif