mpz_ui_pow_ui

[Winfried Dreckmann]

Hi,

The function "mpz_ui_pow_ui" returns the wrong result in certain corner
cases. For instance,

#include <stdio.h>
#include <gmp.h>
int main(int argc, char *argv[])
{
    mpz_t  x;
    mpz_init(x);
    mpz_ui_pow_ui(x, 4UL, 1431655766UL);
    if (mpz_fits_ulong_p(x)) printf("x = %u\n", mpz_get_ui(x));
    return 0;
}

prints "x = 4". There are many similar cases. The reason seems to be an
integer overflow during the computation of low zero bits in
"mpz/n_pow_ui.c".

gmp version: 4.1
machine: PowerPC 604e running Linux 2.2.14
compiler: gcc 2.95.2

Best regards,
Winfried Dreckmann