Integer exponentiation without modulo?

[FX Coudert]

Hi all,

Among the various integer exponentiation functions, I couldn't find  
one that computers a**b, where a and b are both mpz_t. mpz_powm  
performs a modulo operation, and mpz_pow_ui requires that I extract  
an unsigned long int from b, which is not possible if b is large.

Is there any trick to do this? Or a function I overlooked?

Thanks for your help,
FX