mini-gmp test suite could be improved

[Vincent Lefevre]

On 2018-09-05 16:00:18 +0200, Torbjorn Granlund wrote:
> paul zimmermann <Paul.Zimmermann at inria.fr> writes:
> 
>   void
>   mpz_add_ui (mpz_t r, const mpz_t a, unsigned long b)
>   {
>     b = b % 0xffffffff;
>     if (a->_mp_size >= 0)
>       r->_mp_size = mpz_abs_add_ui (r, a, b);
>     else
>       r->_mp_size = -mpz_abs_sub_ui (r, a, b);
>   }
> 
> An interestng approach, patch the library to miscompute things in a way
> that the testsuite does not detect!

I intended to do that in MPFR to check that each MPFR_LIMB() macro
was really needed or something was missing in the test suite.

> Perhaps this can be automated and given a new, trendy name now that
> fuzzing has been on everybody's mind for so long? :-)

An interesting place is to check inequalities on integers, by adding
or subtracting 1 on one side. And some magic constants. But it could
also mean that there are several valid possibilities, and the language
would need to be extended to handle that.

-- 
Vincent Lefèvre <vincent at vinc17.net> - Web: <https://www.vinc17.net/>
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