Possible bug in mini-gmp (gmp-6.0.0)

Zach Metzinger zmetzing at pobox.com
Thu May 14 19:23:21 UTC 2015


While trying to generate the value (2^N)-1 for N := {8,512} and using 
the mini-gmp library, I did the following:

    mpz_set_ui(m, 0);
    mpz_setbit(m, n-1);
    mpz_sub_ui(m, m, 1);

This produced, in the case of N == 0:


While the following code:

    mpz_set_ui(t0, 1);
    mpz_mul_2exp(m, t0, n);
    mpz_sub_ui(m, m, 1);

produces the correct result:


I'm cross-compling from "FreeBSD 9.3-RELEASE" to

arm-none-eabi-gcc (GNU Tools for ARM Embedded Processors) 4.8.3 20140228 (release) [ARM/embedded-4_8-branch revision 208322]

The ultimate target is an ARM Cortex-M4.

This might just be the way it works, but I thought I'd report it.

Let me know if you need more information or additional testing.

--- Zach

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