This line puzzles me a little bit. When you swap classes in the stdlib, you can get unexpected results. Can we replicate this without monkeypatching?

Hi@sobolevn I doubt the possibility of replicating this without monkeypatching. The issue stems from, during a mixed format buffer comparison,memory_richcompare function calls a re-entrantstruct.Struct.unpack_from that is loaded by aPyImport_ImportModuleAttrString("struct", "Struct") call in thestruct_get_unpacker. Is there anyway you would recommend to work around it ?

/* Return a new unpacker for the given format. */staticstructunpacker*struct_get_unpacker(constchar*fmt,Py_ssize_titemsize){    ...// struct.Struct ImportationStruct=PyImport_ImportModuleAttrString("struct","Struct");if (Struct==NULL)returnNULL;x=unpacker_new();    ...x->unpack_from=PyObject_GetAttrString(structobj,"unpack_from");if (x->unpack_from==NULL)        gotoerror;    ...}

There are countless potential issues if we replace stdlib types with something else. Let's please first discuss in the issue whether this is even a valid bug report.

I did consider it as a crash because we also fixed similar occurrences elsewhere. If we just had an exception it would have been ok, but here we have a crash. We do not want this.