mirror of https://github.com/python/cpython
bee112a94d
Users want to know when the current context switches to a different context object. Right now this happens when and only when a context is entered or exited, so the enter and exit events are synonymous with "switched". However, if the changes proposed for gh-99633 are implemented, the current context will also switch for reasons other than context enter or exit. Since users actually care about context switches and not enter or exit, replace the enter and exit events with a single switched event. The former exit event was emitted just before exiting the context. The new switched event is emitted after the context is exited to match the semantics users expect of an event with a past-tense name. If users need the ability to clean up before the switch takes effect, another event type can be added in the future. It is not added here because YAGNI. I skipped 0 in the enum as a matter of practice. Skipping 0 makes it easier to troubleshoot when code forgets to set zeroed memory, and it aligns with best practices for other tools (e.g., https://protobuf.dev/programming-guides/dos-donts/#unspecified-enum). Co-authored-by: Richard Hansen <rhansen@rhansen.org> Co-authored-by: Victor Stinner <vstinner@python.org> |
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| .. | ||
| c_analyzer | ||
| c_common | ||
| c_parser | ||
| cpython | ||
| distutils | ||
| README | ||
| TODO | ||
| c-analyzer.py | ||
| check-c-globals.py | ||
| must-resolve.sh | ||
| table-file.py | ||
README
####################################### # C Globals and CPython Runtime State. CPython's C code makes extensive use of global variables. Each global falls into one of several categories: * (effectively) constants (incl. static types) * globals used exclusively in main or in the REPL * freelists, caches, and counters * process-global state * module state * Python runtime state Of the different categories, the last two are problematic and generally should not exist in the codebase. Globals that hold module state (i.e. in Modules/*.c) cause problems when multiple interpreters are in use. For more info, see PEP 3121, which addresses the situation for extension modules in general. Globals in the last category should be avoided as well. The problem isn't with the Python runtime having state. Rather, the problem is with that state being spread throughout the codebase in dozens of individual globals. Unlike the other globals, the runtime state represents a set of values that are constantly shifting in a complex way. When they are spread out it's harder to get a clear picture of what the runtime involves. Furthermore, when they are spread out it complicates efforts that change the runtime. Consequently, the globals for Python's runtime state have been consolidated under a single top-level _PyRuntime global. No new globals should be added for runtime state. Instead, they should be added to _PyRuntimeState or one of its sub-structs. The check-c-globals script should be run to ensure that no new globals have been added: python3 Tools/c-analyzer/check-c-globals.py You can also use the more generic tool: python3 Tools/c-analyzer/c-analyzer.py If it reports any globals then they should be resolved. If the globals are runtime state then they should be folded into _PyRuntimeState.