Assigning a dict to the memo of an Unpickler object fails

[PCigales]

Bug report

Bug description:

Hi,

When using the C accelerated implementation of the pickle module, assigning a dict to the memo of an Unpickler object leads to clearing the memo.
I think there is an error in Unpickler_set_memo as instructions at lines 7493 to 7495 (MemoCleanup and assignment of new_memo to self->memo) cancels the result of instruction at line 7482 (MemoPut).

Thanks in advance.

CPython versions tested on:

3.12

Operating systems tested on:

Windows

[PCigales]

Assigning a memo from an already used Unpickler object to a brand new one leads to an error ("memo value not found") when trying to use it to unpickle the same byte sequence. I suspect it is because memo_len of target is not set to memo_len from source, either by using _Unpickler_MemoPut after switching to the new blank memo rather than copying or by doing the assignment at the end of Unpickler_set_memo.