qdiv (possibly) modifies its first argument

[videlec]

>>> import gmpy2
>>> a = gmpy2.mpq(1,2)
>>> b = gmpy2.mpq(2,3)
>>> gmpy2.qdiv(a,b)
mpq(3,4)
>>> a   # a gest modified!!!
mpq(3,4)

The reason is that the function GMPy_MPQ_From_Rational does not return a copy of its argument if it is already a rational.

(see also sympy issue #12753)

[casevh]

The following code in gmpy2_mpq_misc.c:

mpq_div(tempx->q, tempx->q, tempy->q);
Py_DECREF((PyObject*)tempy);

should be changed to something like:

tempresult = (PyObject*)GMPy_MPZ_New(context);
mpq_div(tempresult->q, tempx->q, tempy->q);

< do stuff >

Py_DECREF(tempresult);

Obviously needs error checking and other changes.

I can work on a complete fix in the next couple of days.

[videlec]

Thanks. Note that sympy is wrongly using qdiv and I will provide an easier fix for them.

[casevh]

I've pushed a fix. Thanks for the report.