bug report

[Anne-Marie GASTINEAU]

I found an optimization bug on my linux box with the gcc compiler (gcc
coming with Mandrake 7.1).

There is a problem with the conversion : intmax_t -> double -> intmax_t.
The correct result is given with the option -O0.
If I remove the keyword volatile from l1, the problem is the same.

The attached file  are :
toto.O0.i and toto.O0.s are the intermediate file from -O0 compilation.
toto.O2.i and toto.O2.s are the intermediate file from -O0 compilation.


[bdl@localhost user]$ gcc --version
2.95.3

[bdl@localhost user]$ uname -a
Linux localhost.localdomain 2.2.15-4mdk #4 mer sep 20 21:02:27 CEST 2000
i586 unknown

[bdl@localhost user]$ gcc -O0 toto.c -o toto
[bdl@localhost user]$ ./toto
v=2305843009213693952
v=2305843009213693953
l>l1
v=2305843009213693951
l<l1
[bdl@localhost user]$ gcc -O2 toto.c -o toto
[bdl@localhost user]$ ./toto
v=2305843009213693952
v=2305843009213693953
v=2305843009213693951

My prgram is :
#include <stdio.h>
#include <inttypes.h>

void  LONGLONG22DBL(intmax_t l)
{
 double d1, d2;
 volatile intmax_t l1;
 d1 = l;
 d2 = d1;
 l1 = d1;
 if ( l<l1 )
 {
   printf("l<l1\n");
 }
 else if ( l>l1 )
 {
  printf("l>l1\n");
 }
}


int main()
{
 intmax_t v=1;
 v <<=61;
 printf("v=%"PRIiMAX"\n",v);
 LONGLONG22DBL(v);
 v+=1;
 printf("v=%"PRIiMAX"\n",v);
 LONGLONG22DBL(v);
 v-=2;
 printf("v=%"PRIiMAX"\n",v);
 LONGLONG22DBL(v);
 return 0;
}








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