gh-117139: Convert the evaluation stack to stack refs#118450
Merged
Fidget-Spinner merged 152 commits intopython:mainfrom Jun 26, 2024
Merged
gh-117139: Convert the evaluation stack to stack refs#118450Fidget-Spinner merged 152 commits intopython:mainfrom
Fidget-Spinner merged 152 commits intopython:mainfrom
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This PR sets up tagged pointers for CPython.
The general idea is to create a separate struct
_PyStackReffor everything on the evaluation stack to store the bits. This forces the C compiler to warn us if we try to cast things or pull things out of the struct directly.Only for free threading: We tag the low bit if something is deferred - that means we skip incref and decref operations on it. This behavior may change in the future if Mark's plans to defer all objects in the interpreter loop pans out.
This implies a strict stack reference discipline is required. ALL incref and decref operations on stackrefs must use the stackref variants. It is unsafe to untag something then do normal incref/decref ops on it.
The new incref and decref variants are called dup and close. They mimic a "handle" API operating on these stackrefs.
Please read
Include/internal/pycore_stackref.hfor more information!