In 3.11 we're changing a lot of details about code objects. Part of this is the "Faster CPython" work, part of it is other things (e.g. PEP 657 -- Fine Grained Error Locations in Tracebacks).
As a result, the set of fields of the code object is changing. This is fine, the structure is part of the internal API anyway. But there's a problem with two public API functions, PyCode_New() and PyCode_NewWithPosArgs(). As we have them in the main (3.11) branch, their signatures are incompatible with previous versions, and they have to be since the set of values needed to create a code object is different. (The types.CodeType constructor signature is also changed, and so is its replace() method, but these aren't part of any stable API). Unfortunately, PyCode_New() and PyCode_NewWithPosArgs() are part of the PEP 387 stable ABI. What should we do? A. We could deprecate them, keep (restore) their old signatures, and create crippled code objects (no exception table, no endline/column tables, qualname defaults to name). B. We could deprecate them, restore the old signatures, and always raise an error when they are called. C. We could just delete them. D. We could keep them, with modified signatures, and to heck with ABI compatibility for these two. E. We could get rid of PyCode_NewWithPosArgs(), update PyCode() to add the posonlyargcount (which is the only difference between the two), and d*mn the torpedoes. F. Like (E), but keep PyCode_NewWithPosArgs() as an alias for PyCode_New() (and deprecate it). If these weren't part of the stable ABI, I'd choose (E). But because they are, I think only (A) or (B) are our options. The problem with (C) is that if there's code that links to them but doesn't call them (except in some corner case that the user can avoid), the code won't link even though it would work fine. The problem with (D) is that if it *is* called by code expecting the old signature it will segfault. I'm not keen on (A) since it can cause broken code objects when used to copy a code object with some modified metadata (e.g. a different filename), since there's no way to pass the exception table (and several other fields, but the exception table is an integral part of the code now). Code wanting to make slight modifications to code objects such as changing co_name or co_filename should switch to the .replace() API, which is much better at this (though calling it from C is a pain, it's possible). Code wanting to synthesize code should be updated for each release; we should probably require such code to be built with the internal API and use _PyCode_New(), which takes a struct argument containing all the necessary fields. Thoughts? I'm especially interested in Petr's opinion given that this is a case where we'd like to deprecate something in the stable ABI. See also discussion in https://bugs.python.org/issue40222 (esp. near the end). -- --Guido van Rossum (python.org/~guido) *Pronouns: he/him **(why is my pronoun here?)* <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
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