bpo-29548: Recommend PyObject_Call APIs over PyEval_Call APIs. by methane · Pull Request #75 · python/cpython

Co-authored-by: Jules <julia.poo.poo.poo@gmail.com>

Stay at eol when moving up/down

Prevents accidental shallow copy of raw MemoryIndirect* in value_.indirect,
which would create double-free risk. The copy constructor deliberately skips
value_ (safe); this ensures assignment doesn't silently shallow-copy it.

Per gatekeeper recommendation (20:34) and Pythia assessment python#75.

C++ destroys members in reverse declaration order. With cfg before env,
env destructs first — freeing Registers while cfg still holds
Instructions with FrameState Register* pointers into env memory.

Swap: env now declared before cfg, so env outlives cfg during
destruction. FrameState's borrowed Register* pointers remain valid
throughout cfg teardown.

Found by Pythia assessment python#75. Currently safe by coincidence
(~FrameState only frees the buffer, never dereferences), but any
future dereference during destruction would be use-after-free.

ARM64 pydebug shutdown SEGV root-cause: GlobalCacheKey holds raw
PyDictObject* pointers to globals/builtins. When globals is freed
during Py_FinalizeEx (interpreter_clear → PyDict_Clear), the cache
entry remains in map_ + watch_map_[builtins]. Subsequent
PyDict_EVENT_CLEARED on builtins triggers updateCache, which derefs
cache.key().globals → use-after-free. Pydebug poison fill (0xdd...)
makes the UAF a hard SEGV; x86_64 release reads stale-but-readable
type pointer and silently passes the JIT_CHECK.

Two surgical guards address the FINALIZE-SPECIFIC manifestation:

  Part A — Python/jit_support/phoenix_init.cpp
    phoenix_dict_watcher early-returns when Py_IsFinalizing(). Cache
    state is about to be destroyed in phoenix_free; processing events
    on tearing-down dicts is moot. Pattern matches pyjit.cpp:1642
    funcDestroyed precedent.

  Part B — Python/jit/global_cache.cpp
    GlobalCacheManager::clear() short-circuits when Py_IsFinalizing().
    Avoids two failure modes:
      1. Ci_Watchers_UnwatchDict (PyDict_Unwatch) reads dict internals
         on freed memory → UAF under pydebug
      2. ci_watcher_state_fini ran first in phoenix_free → watcher_id
         is -1 → JIT_CHECK 'Invalid dict watcher ID -1' abort
         (observed in earlier gate logs, regression historically)

SCOPE HONESTY: this is FINALIZE-SPECIFIC protection, NOT full
root-cause for the raw-pointer-aliasing class. Mid-execution module
unload (refcount→0 on globals while cache holds raw pointer) remains
unaddressed. Filed as W27 GlobalCacheKey raw-pointer lifecycle
re-architecture (docs/w27-globalcachekey-lifecycle.md, Tier 6+ scope).
The 314d0f2 'weak reference semantics' comment was FALSIFIED — no
mechanism actually provided weak-reference semantics; comments updated
to name the actual mechanisms (Py_IsFinalizing guard, finalize-only
protection).

Diagnostic evidence (per Debug-First protocol):
  lldb backtrace on ARM64 pydebug push 59 falsifier:
    PyType_HasFeature(type=0xdddddddddddddddd) object.h:966  <-- SEGV
    hasOnlyUnicodeKeys()                       dict.h:52
    GlobalCacheManager::updateCache()          global_cache.cpp:325
    GlobalCacheManager::notifyDictClear()      global_cache.cpp:144
    phoenix_dict_watcher()                     phoenix_init.cpp:58
    PyDict_Clear → interpreter_clear → Py_FinalizeEx

Test plan post-commit:
  testkeeper ARM64 pydebug --clean rebuild + falsifier rerun
  (test_phoenix_jit_inline_except_closure under timeout+redirect)
  + push 58 baseline regression check (8b7b935 still passes).

testkeeper x86_64 compile-only PASS verified pre-commit at
binary timestamp 1776874355 (chat L1872 build verification).

Authorization chain: supervisor option (i) at chat L1862, theologian
LEVEL-1 ratification at chat L1861. Pythia python#75 python#1 (trigger isolation)
gates downstream emitCallExceptionHandler queue, NOT this fix.

Per pythia python#76 [chat 16:45Z] + supervisor revision [chat 16:45Z python#3]:
filed-not-owned workstreams accrue weed-debt ('a field marked for
fallow grows weeds named next year'). W27 was filed at bf8982b
without ownership, falsification test, or revisit-trigger.

Added §1 frontmatter:
  - Owner: theologian (design), generalist (implementation)
  - Schedule: entry-trigger = Tier 5 ZERO C++ complete + no active
    push-class blocker; exit by start of cinderx Tier 6 cleanup
  - Falsification test reference: §8

Added §8 falsification test sketch:
  Lib/test/test_phoenix_w27_module_unload_uaf.py
  - SKIPPED until W27 work begins
  - Reproducer: register cache entry → del sys.modules → gc.collect →
    fire builtins event → expect SEGV pre-W27 / clean post-W27
  - Acceptance: reproduces SEGV pre-W27 + passes post-W27, OR W27
    scope re-opens if reproducer is harder to trigger than predicted
  - Discipline: 'falsification-first' — test lands before fix code

Added §7 cross-references:
  - Push 58 ARM64-pydebug coredump finding from testkeeper [chat
    16:45Z]: 8b7b935 baseline ALSO produces shutdown coredump
    on the same falsifier workload (just non-deterministic vs push
    59's deterministic SEGV) — independent confirmation that this
    is pre-existing latent (pythia python#75 b1 outcome) not push-59-port-
    shape-specific
  - W27 ownership update authority chain

This commit IS supervisor's pythia python#76 python#3 corrective action — turning
'filed' into 'owned, scheduled, testable'. Pattern reusable: same
audit will be applied to W23 (verifier hardening), W25 (typed bridges),
W26 (build-state hardening) per supervisor [chat 16:45Z python#3] deferral.