Package: gcc-3.2
Version: 1:3.2.3-8
Severity: normal
I am not used to go this deep in code, i would appreciate any critisicm
regarding this report and the time you use on it.i If you think this
have nothing to do with gcc , i d be happy with this being reassigned to
the proper maintenair.
Is it ok that double operators give diferents results with athlon
TB than with other processors ?
Following some mozilla debugging i ended on a "if (10*double)" test in a
while statement.
The test work with the same binary under Athlon XP/Pentium porcessors but not
with Athlon Thunderbird.
I isolated the whole conditional test in a file:
mozjstest.c: the bad behaviour appear for testlimit >=5
using print or a temporary variable round the d value correctly and
fix the problem, i found out the wrong values with gdb print.
to have the bug as in mozilla i multiplied d by 10 (as the mozilla
code do) , then even print is not able to round d value correctly
(why on athlon TB only ?).
extract from the real mozilla code (cf bug #203100):
d, ds are double; L a long
L = (Long) (d / ds);
d -= L*ds;
on athlon "d - d != 0" (especially d -= L*ds) though it is on other
processors (still same binary)
the loop is ended by:
if (!(d *= 10.))
break;
and d never equals 0
Alban
-- System Information:
Debian Release: testing/unstable
Architecture: i386
Kernel: Linux argos 2.6.0-test8 #12 Sun Oct 19 04:44:52 CEST 2003 i686
Locale: [EMAIL PROTECTED], [EMAIL PROTECTED]
Versions of packages gcc-3.2 depends on:
ii binutils 2.14.90.0.6-3 The GNU assembler, linker and bina
ii cpp-3.2 1:3.2.3-8 The GNU C preprocessor
ii gcc-3.2-base 1:3.2.3-8 The GNU Compiler Collection (base
ii libc6 2.3.2-8 GNU C Library: Shared libraries an
ii libgcc1 1:3.3.2-0pre5 GCC support library
-- no debconf information
#include <stdio.h>
// d is calculated through my use of he c temp double to fix the rounding error
// dold does exactly what the code in gecko does
// note that d/dold are tested in gecko as the breaking condition after being multiplied by ten.
// i set L as long (on my platform it s equal to uint32 whiwh is the Long type used by mozilla
int main(){
// those values are those i got from my instance of mozilla
double d=5000340000.;
double dold=5000340000.;
double ds=1000000000.;
long L;
double c;
int testlimit = 6;
int i = 1;
for(i=1;i<testlimit;i++){
L = (long) (d/ds);
c= L*ds;
d -= c;
d*=10;
printf("d n°%d: %f\n",i,d);
}
for(i=1;i<testlimit;i++){
L = (long) (dold/ds);
dold -= L*ds;
dold*=10;
printf("dold n°%d: %f\n",i,dold);
}
printf("%f %f %f \n",d, dold, c);
return 0;
}
