strtod (and atof) on hex numbers

Paul Biggar
Tue Jun 20 17:02:00 GMT 2006


atof (and hence strtod) on hexadecimal numbers results in 0.0 (errno
of 0). This may be related to an old issue where NaN isnt correctly
parsed. I believe it isnt correct behaviour:

I've tested it for integers in the range 0x8000000 to 0xFFFFFFFF. It
works properly on

ubuntu dapper, gcc 4.1 on i386;
debian stable, gcc 3.3 on amd64
sunos ?, gcc 3.4 on sparc

I'm using standard cygwin distribution, which uses gcc 3.4.4 (cygming special)

Sample code:

#include "limits.h"
#include <iostream.h>
#include "errno.h"

int main()

        cout << ULONG_MAX << endl;
        cout << 0xFFFFFFFF << endl;

        errno = 0;
        cout << atof("0xFFFFFFFF") << endl;
        cout << errno << endl;

        errno = 0;
        cout << strtod("0xFFFFFFFF", NULL) << endl;
        cout << errno << endl;


Is this being fixed? I could find a mention of it before. Does anyone
know a simple workaround?


Paul Biggar

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