On 2016-04-06 17:39:21 +0200, Torbjörn Granlund wrote:
> Miha Marolt <mi...@beyondsemi.com> writes:
>
> In some cases a previously freed memory is read inside the mpz_sub
> function. Here is an example program that demonstrates the
> problem:
>
> The bug is in your code.
>
> When passing x by value, you make copies of the two contained mpz_t
> variables, including pointers. Then you cause reallocation of the
> original variables, making pointer your copies point to stale data.
However, the GMP manual says:
[...] Here are some examples of how to declare such integers:
mpz_t sum;
struct foo { mpz_t x, y; };
mpz_t vec[20];
and doesn't forbid to copy the structure, for instance. I think it
would be worth to mention that using several copies of a mpz_t is
forbidden (or a write operation invalidates the other copies),
here or in one of the next sections (BTW, the MPFR manual should
be clarified too).
--
Vincent Lefèvre <vinc...@vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
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