[issue15870] PyType_FromSpec should take metaclass as an argument
Josh Haberman
report at bugs.python.org
Tue Sep 28 15:11:53 EDT 2021
Josh Haberman <haberman at google.com> added the comment:
> Everything is copied by `_FromSpec` after all.
One thing I noticed isn't copied is the string pointed to by tp_name: https://github.com/python/cpython/blob/0c50b8c0b8274d54d6b71ed7bd21057d3642f138/Objects/typeobject.c#L3427
This isn't an issue if tp_name is initialized from a string literal. But if tp_name is created dynamically, it could lead to a dangling pointer. If the general message is that "everything is copied by _FromSpec", it might make sense to copy the tp_name string too.
> However, I suppose that would replace a safe-by-design API with a "best practice" to never define the spec/slots statically (a best practice that is probably not generally followed or even advertised currently, I guess).
Yes that seems reasonable. I generally prefer static declarations, since they will end up in .data instead of .text and will avoid a copy to the stack at runtime. But these are very minor differences, especially for code that only runs once at startup, and a safe-by-default recommendation of always initializing PyType_* on the stack makes sense.
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