> static int ftruncate64 (int fd, curl_off_t where)
> {
> if (_lseeki64(fd, where, SEEK_SET) < 0)
> return -1;
>
> if (!SetEndOfFile((HANDLE)_get_osfhandle(fd)))
> return -1;
>
> return 0;
> }

I agree with this.

Attached patch also defines HAVE_FTRUNCATE for WIN32 so that
ftruncate64() is actually used.

Please verify if it is ok for you.

If you give us your full name, credit will go to you when commiting
this bug fix.

-- 
-=[Yang]=-