New comment by tornaria on void-packages repository

https://github.com/void-linux/void-packages/pull/34030#issuecomment-1000816549

Comment:
Then the library is ok, so this points to an issue with `PY_NEW()` not allocating properly, in such a way that it only triggers the second branch of `mpz_fac_ui`...

Try `sage.rings.integer.Integer.factorial(27)` on `sage --valgrind`; but if that doesn't give good information the only thing I can think of is to patch the function to print stuff about z.value after `PY_NEW(Integer)` but before `sig_on()`.

Maybe something like (untested):
```
cdef mpz_ptr zz
zz = <mpz_ptr>(z.value)
print(zz._mp_alloc, zz._mp_size, zz._mp_d)
```

I don't know if we can use `print()` on these C types. Maybe the way is something like `printf("%d %d %p\n", zz._mp_alloc, zz._mp_size, zz._mp_d)`.

Alternatively, try to step this function in gdb and look at these values.