[Bug c++/35556] New: problem with log10 and arch x86_64

[laura at filmlight dot ltd dot uk]

log10 in a 64 bit Intel build on OS X sometimes returns a result of 0, no
matter what the argument.

gcc version:

Using built-in specs.
Target: i686-apple-darwin9
Configured with: /var/tmp/gcc/gcc-5465~16/src/configure --disable-checking
-enable-werror --prefix=/usr --mandir=/sh
are/man --enable-languages=c,objc,c++,obj-c++
--program-transform-name=/^[cg][^.-]*$/s/$/-4.0/ --with-gxx-include-di
r=/include/c++/4.0.0 --with-slibdir=/usr/lib --build=i686-apple-darwin9
--with-arch=apple --with-tune=generic --host
=i686-apple-darwin9 --target=i686-apple-darwin9
Thread model: posix
gcc version 4.0.1 (Apple Inc. build 5465)


The program is compiled using g++ -arch x86_64 bug_check.cpp

There are no compiler warnings.
When run (no arguments on the command line), the first loop produces correct
values, but the second produces all 0 results.



double broken_log10(double val)
{
    return log10(val);
}

double working_log10(double val)
{
    double t = log10(val);
    printf("%g\n", val);
    return t;
}

int main(int argc, char **argv)
{
    int n;
    int len = 10;

    for (n = 1; n < len; n++)
    {
 printf("%d: %g\n", n, working_log10((double)n/(double)len));
    }
    for (n = 1; n < len; n++)
    {
 printf("%d: %g\n", n, broken_log10((double)n/(double)len));
    }
    return 0;
}


-- 
           Summary: problem with log10 and arch x86_64
           Product: gcc
           Version: 4.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: laura at filmlight dot ltd dot uk
 GCC build triplet: i686-apple-darwin9
  GCC host triplet: i686-apple-darwin9
GCC target triplet: i686-apple-darwin9


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35556