linux i-86 problem with rounding (gcc-3.1.1 & 3.2)

["Hillel (Sabba) Markowitz" <sabbahem@bcpl.net>]

The following test program give incorrect results in a cast from double to int 
when compiled without an optimization option but correct results when compiled 
with an optimization option.

int main(int argc, char **argv)
{
  int i = 128000;
  double f = 0.0075;
  double g;
  unsigned int u;

  u = (unsigned int) (i*f);
  printf("unsigned int result of i*f: %u\n", u);

  g = i*f;
  u = (unsigned int)g;
  printf("double result: %lf\n", g);
  printf("unsigned int result: %u\n", u);

  return(0);
}


%gcc testfloat.c -o testfloat
%./testfloat

unsigned int result of i*f: 959
double result: 960
unsigned int result: 960

%gcc testfloat.c -o testfloat -O
%./testfloat

unsigned int result of i*f: 960
double result: 960
unsigned int result: 960


This error occurs only on the linux i-86 (redhat 7.2 or 7.3).  However, the 
results come out correctly on Solaris, DEC (4.0 and 5.1) and linux alpha 
(redhat 7.2).

Does anyone have an idea for a fix or workaround?  Is this an artifact of the 
Assembler or the floating point co-processor?  Is this something to do with 
gcc?

Please e-mail me with the answer as well as the mailing list.

Thanks,

-- 
Said the fox to the fish, "Join me ashore".
 The fish are the Jews, Torah is our water

Hillel (Sabba) Markowitz - sabbahem@bcpl.net