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gh-113993: Allow interned strings to be mortal, and fix related issues (GH-120520)

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* 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.

* For free-threaded builds, intern `_Py_LATIN1_CHR` singletons at startup.

* Beef up the tests. Cover internal details (marked with `@cpython_only`).

* Add lots of assertions

Co-Authored-By: Eric Snow <ericsnowcurrently@gmail.com>
This commit is contained in:
Petr Viktorin 2024-06-21 17:19:31 +02:00 • committed by GitHub
parent 7595e6743a
commit 6f1d448bc1
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42 changed files with 2464 additions and 1140 deletions
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6
Python/codecs.c
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@ -147,7 +147,9 @@ PyObject *_PyCodec_Lookup(const char *encoding)
if (v == NULL) {
return NULL;
}
PyUnicode_InternInPlace(&v);
/* Intern the string. We'll make it immortal later if lookup succeeds. */
_PyUnicode_InternMortal(interp, &v);
/* First, try to lookup the name in the registry dictionary */
PyObject *result;
@ -200,6 +202,8 @@ PyObject *_PyCodec_Lookup(const char *encoding)
goto onError;
}
_PyUnicode_InternImmortal(interp, &v);
/* Cache and return the result */
if (PyDict_SetItem(interp->codecs.search_cache, v, result) < 0) {
Py_DECREF(result);