Petr Viktorin 49f6beb56a [3.12] gh-113993: Make interned strings mortal (GH-120520, GH-121364, GH-121903, GH-122303) (#123065) ... This backports several PRs for gh-113993, making interned strings mortal so they can be garbage-collected when no longer needed. * Allow interned strings to be mortal, and fix related issues (GH-120520) * Add an InternalDocs file describing how interning should work and how to use it. * Add internal functions to *explicitly* request what kind of interning is done: - `_PyUnicode_InternMortal` - `_PyUnicode_InternImmortal` - `_PyUnicode_InternStatic` * Switch uses of `PyUnicode_InternInPlace` to those. * Disallow using `_Py_SetImmortal` on strings directly. You should use `_PyUnicode_InternImmortal` instead: - Strings should be interned before immortalization, otherwise you're possibly interning a immortalizing copy. - `_Py_SetImmortal` doesn't handle the `SSTATE_INTERNED_MORTAL` to `SSTATE_INTERNED_IMMORTAL` update, and those flags can't be changed in backports, as they are now part of public API and version-specific ABI. * Add private `_only_immortal` argument for `sys.getunicodeinternedsize`, used in refleak test machinery. Make sure the statically allocated string singletons are unique. This means these sets are now disjoint: - `_Py_ID` - `_Py_STR` (including the empty string) - one-character latin-1 singletons Now, when you intern a singleton, that exact singleton will be interned. * Add a `_Py_LATIN1_CHR` macro, use it instead of `_Py_ID`/`_Py_STR` for one-character latin-1 singletons everywhere (including Clinic). * Intern `_Py_STR` singletons at startup. * Beef up the tests. Cover internal details (marked with `@cpython_only`). * Add lots of assertions * Don't immortalize in PyUnicode_InternInPlace; keep immortalizing in other API (GH-121364) * Switch PyUnicode_InternInPlace to _PyUnicode_InternMortal, clarify docs * Document immortality in some functions that take `const char *` This is PyUnicode_InternFromString; PyDict_SetItemString, PyObject_SetAttrString; PyObject_DelAttrString; PyUnicode_InternFromString; and the PyModule_Add convenience functions. Always point out a non-immortalizing alternative. * Don't immortalize user-provided attr names in _ctypes * Immortalize names in code objects to avoid crash (GH-121903) * Intern latin-1 one-byte strings at startup (GH-122303) There are some 3.12-specific changes, mainly to allow statically allocated strings in deepfreeze. (In 3.13, deepfreeze switched to the general `_Py_ID`/`_Py_STR`.) Co-authored-by: Eric Snow <ericsnowcurrently@gmail.com>		2024-09-27 13:28:48 -07:00
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string_interning.md