Cpython: when to incref before insertdict

[Marco Sulla]

On Sun, 6 Mar 2022 at 03:20, Inada Naoki <songofacandy at gmail.com> wrote:
> In general, when reference is borrowed from a caller, the reference is
> available during the API.
> But merge_dict borrows reference of key/value from other dict, not caller.
> [...]
> Again, insertdict takes the reference. So _PyDict_FromKeys() **does**
> INCREF before calling insertdict, when key/value is borrowed
> reference.
> https://github.com/python/cpython/blob/6927632492cbad86a250aa006c1847e03b03e70b/Objects/dictobject.c#L2287-L2290
> https://github.com/python/cpython/blob/6927632492cbad86a250aa006c1847e03b03e70b/Objects/dictobject.c#L2309-L2311
>
> On the other hand, slow path uses PyIter_Next() which returns strong
> reference. So no need to INCREF it.

Thank you Inada, these points make me things clear now.
(PS: dictobject will change a lot in 3.11... sigh :D)