[kaffe] Re: The problem of "Double.c and buggy strtod" is settled

[Dalibor Topic]

Hi Ito,

--- Dalibor Topic <robilad at yahoo.com> wrote:
> 
> --- Ito Kazumitsu <kaz at maczuka.gcd.org> wrote:
> > >>>>> "*" == Ito Kazumitsu <kaz at maczuka.gcd.org> writes:
> > 
> > *> In fact, FreeBSD 4.7-RELEASE's /usr/include/float.h says
> > *> #define DBL_MIN         2.2250738585072014E-308
> > *> and replace/strtod.c says, when HAVE_FLOAT_H is undefined,
> > *> almost the same thing:
> > *> # define DBL_MIN 2.2250738585072010e-308
> > *> I remember Linux 2.0.x's float.h also defines something like this.
> > *> 
> > *> So Java's double MIN_VALUE 4.9406564584124654418e-324 will be
> > *> considered to be 0.0 by this strtod.c.
> > 
> > Studying this issue further,  I found that DBL_MIN is not the only
> > factor that makes strtod convert 4.9406564584124654418e-324 to 0.0.
> > 
> > Even if I comment out 
> >        if (num < DBL_MIN * pow (10.0, (double) -exponent))
> >         goto underflow;
> > this strtod converts 4.9406564584124654418e-324 to 0.0 although
> > errno is not set.
> > 
> > Inserting "printf("## num, exp = %f, %d\n", num, exponent);"
> > before "num *= pow (10.0, (double) exponent);",  I get
> > "## num, exp = 49406564584124661760.000000, -343".  So
> > the reason why 4.9406564584124654418e-324 becomes 0.0
> > seems to be the limitation of the function pow().
> 
> o.k., since the strtod from libit doesn't work, the one from libiberty (gcc)
> doesn't work either, I'll see if I can get the one from NetBSD to work, since
> you've had some success with it. 

the netbsd strtod seems to need some includes that I don't have around, and the
netlib strtod wants me to specify way more about IEEE than I know ;) The one
from glibc is entangles in the glibc mess of headers, so I took another look at
the one from libiberty. I hope that the attached patch works, I've tried a
slightly adapted DoubleTest.c and it worked for me:

bash-2.05a$ gcc -g DoubleTest.c libiberty-strtod.c safe-ctype.c -I .
bash-2.05a$ ./a.out 4.9406564584124654418e-324
4.9406564584124654418e-324 0              4.94065645841246544177e-324
bash-2.05a$ cat DoubleTest.c
#include <stdlib.h>
extern int errno;

int main(int argc, char* argv[]) {
   double d = strtod(argv[1], NULL);
   printf("%s %d %40.20e\n",argv[1], errno, d);
}

cheers,
dalibor topic

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