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345cd37abe
The original tool wasn't working right and it was simpler to create a new one, partially re-using some of the old code. At this point the tool runs properly on the master. (Try: ./python Tools/c-analyzer/c-analyzer.py analyze.) It take ~40 seconds on my machine to analyze the full CPython code base. Note that we'll need to iron out some OS-specific stuff (e.g. preprocessor). We're okay though since this tool isn't used yet in our workflow. We will also need to verify the analysis results in detail before activating the check in CI, though I'm pretty sure it's close. https://bugs.python.org/issue36876
46 lines
1.9 KiB
Plaintext
46 lines
1.9 KiB
Plaintext
#######################################
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# C Globals and CPython Runtime State.
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CPython's C code makes extensive use of global variables. Each global
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falls into one of several categories:
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* (effectively) constants (incl. static types)
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* globals used exclusively in main or in the REPL
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* freelists, caches, and counters
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* process-global state
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* module state
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* Python runtime state
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The ignored-globals.txt file is organized similarly. Of the different
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categories, the last two are problematic and generally should not exist
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in the codebase.
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Globals that hold module state (i.e. in Modules/*.c) cause problems
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when multiple interpreters are in use. For more info, see PEP 3121,
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which addresses the situation for extension modules in general.
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Globals in the last category should be avoided as well. The problem
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isn't with the Python runtime having state. Rather, the problem is with
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that state being spread throughout the codebase in dozens of individual
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globals. Unlike the other globals, the runtime state represents a set
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of values that are constantly shifting in a complex way. When they are
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spread out it's harder to get a clear picture of what the runtime
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involves. Furthermore, when they are spread out it complicates efforts
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that change the runtime.
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Consequently, the globals for Python's runtime state have been
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consolidated under a single top-level _PyRuntime global. No new globals
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should be added for runtime state. Instead, they should be added to
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_PyRuntimeState or one of its sub-structs. The check-c-globals script
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should be run to ensure that no new globals have been added:
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python3 Tools/c-analyzer/check-c-globals.py
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You can also use the more generic tool:
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python3 Tools/c-analyzer/c-analyzer.py
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If it reports any globals then they should be resolved. If the globals
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are runtime state then they should be folded into _PyRuntimeState.
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Otherwise they should be added to ignored-globals.txt.
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