Original patch from: perfpow.c.diff

 -= BEGIN original header =-

 Copyright 1998, 1999, 2000, 2001, 2005, 2008 Free Software Foundation, Inc.

 This file is part of the GNU MP Library.

 The GNU MP Library is free software; you can redistribute it and/or modify

 it under the terms of the GNU Lesser General Public License as published by

 the Free Software Foundation; either version 3 of the License, or (at your

 option) any later version.

 The GNU MP Library is distributed in the hope that it will be useful, but

 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY

 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public

 License for more details.

 You should have received a copy of the GNU Lesser General Public License

 along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.

 -= END original header =-

 diff -durN gmp-4.2.4.orig/mpz/perfpow.c gmp-4.2.4/mpz/perfpow.c

 --- gmp-4.2.4.orig/mpz/perfpow.c	2007-08-30 20:31:41.000000000 +0200

 +++ gmp-4.2.4/mpz/perfpow.c	2009-03-08 18:36:16.000000000 +0100

 @@ -1,7 +1,7 @@

  /* mpz_perfect_power_p(arg) -- Return non-zero if ARG is a perfect power,

     zero otherwise.

 -Copyright 1998, 1999, 2000, 2001, 2005 Free Software Foundation, Inc.

 +Copyright 1998, 1999, 2000, 2001, 2005, 2008 Free Software Foundation, Inc.

  This file is part of the GNU MP Library.

 @@ -59,6 +59,8 @@

  #define SMALLEST_OMITTED_PRIME 1009

 +#define POW2P(a) (((a) & ((a) - 1)) == 0)

 +

  int

  mpz_perfect_power_p (mpz_srcptr u)

  {

 @@ -72,16 +74,13 @@

    mp_size_t usize = SIZ (u);

    TMP_DECL;

 -  if (usize == 0)

 -    return 1;			/* consider 0 a perfect power */

 +  if (mpz_cmpabs_ui (u, 1) <= 0)

 +    return 1;			/* -1, 0, and +1 are perfect powers */

    n2 = mpz_scan1 (u, 0);

    if (n2 == 1)

      return 0;			/* 2 divides exactly once.  */

 -  if (n2 != 0 && (n2 & 1) == 0 && usize < 0)

 -    return 0;			/* 2 has even multiplicity with negative U */

 -

    TMP_MARK;

    uns = ABS (usize) - n2 / BITS_PER_MP_LIMB;

 @@ -89,6 +88,14 @@

    MPZ_TMP_INIT (u2, uns);

    mpz_tdiv_q_2exp (u2, u, n2);

 +  mpz_abs (u2, u2);

 +

 +  if (mpz_cmp_ui (u2, 1) == 0)

 +    {

 +      TMP_FREE;

 +      /* factoring completed; consistent power */

 +      return ! (usize < 0 && POW2P(n2));

 +    }

    if (isprime (n2))

      goto n2prime;

 @@ -97,6 +104,9 @@

      {

        prime = primes[i];

 +      if (mpz_cmp_ui (u2, prime) < 0)

 +	break;

 +

        if (mpz_divisible_ui_p (u2, prime))	/* divisible by this prime? */

  	{

  	  rem = mpz_tdiv_q_ui (q, u2, prime * prime);

 @@ -115,12 +125,6 @@

  	      n++;

  	    }

 -	  if ((n & 1) == 0 && usize < 0)

 -	    {

 -	      TMP_FREE;

 -	      return 0;		/* even multiplicity with negative U, reject */

 -	    }

 -

  	  n2 = gcd (n2, n);

  	  if (n2 == 1)

  	    {

 @@ -128,10 +132,11 @@

  	      return 0;		/* we have multiplicity 1 of some factor */

  	    }

 -	  if (mpz_cmpabs_ui (u2, 1) == 0)

 +	  if (mpz_cmp_ui (u2, 1) == 0)

  	    {

  	      TMP_FREE;

 -	      return 1;		/* factoring completed; consistent power */

 +	      /* factoring completed; consistent power */

 +	      return ! (usize < 0 && POW2P(n2));

  	    }

  	  /* As soon as n2 becomes a prime number, stop factoring.

 @@ -169,6 +174,10 @@

    else

      {

        unsigned long int nth;

 +

 +      if (usize < 0 && POW2P(n2))

 +	return 0;

 +

        /* We found some factors above.  We just need to consider values of n

  	 that divides n2.  */

        for (nth = 2; nth <= n2; nth++)

 @@ -184,8 +193,11 @@

  	    exact = mpz_root (q, u2, nth);

  	  if (exact)

  	    {

 -	      TMP_FREE;

 -	      return 1;

 +	      if (! (usize < 0 && POW2P(nth)))

 +		{

 +		  TMP_FREE;

 +		  return 1;

 +		}

  	    }

  	  if (mpz_cmp_ui (q, SMALLEST_OMITTED_PRIME) < 0)

  	    {

 @@ -199,6 +211,9 @@

      }

  n2prime:

 +  if (usize < 0 && POW2P(n2))

 +    return 0;

 +

    exact = mpz_root (NULL, u2, n2);

    TMP_FREE;

    return exact;