[Python-checkins] GH-94893: Ignore caches when adding LOAD_FAST_CHECKs (GH-94894)

[brandtbucher]

https://github.com/python/cpython/commit/b407312a24f12de76a928394099decd64f6049a6
commit: b407312a24f12de76a928394099decd64f6049a6
branch: main
author: Brandt Bucher <brandtbucher at microsoft.com>
committer: brandtbucher <brandtbucher at gmail.com>
date: 2022-07-18T09:00:41-07:00
summary:

GH-94893: Ignore caches when adding LOAD_FAST_CHECKs (GH-94894)

files:
A Misc/NEWS.d/next/Core and Builtins/2022-07-15-22-47-44.gh-issue-94893.YiJYcW.rst
M Objects/frameobject.c

diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-07-15-22-47-44.gh-issue-94893.YiJYcW.rst b/Misc/NEWS.d/next/Core and Builtins/2022-07-15-22-47-44.gh-issue-94893.YiJYcW.rst
new file mode 100644
index 0000000000000..6384ef92c6543
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2022-07-15-22-47-44.gh-issue-94893.YiJYcW.rst	
@@ -0,0 +1,2 @@
+Fix an issue where frame object manipulations could corrupt inline bytecode
+caches.
diff --git a/Objects/frameobject.c b/Objects/frameobject.c
index 3e97b75d4bf5a..fe8eaa341fb33 100644
--- a/Objects/frameobject.c
+++ b/Objects/frameobject.c
@@ -603,7 +603,8 @@ add_load_fast_null_checks(PyCodeObject *co)
     int changed = 0;
     _Py_CODEUNIT *instructions = _PyCode_CODE(co);
     for (Py_ssize_t i = 0; i < Py_SIZE(co); i++) {
-        switch (_Py_OPCODE(instructions[i])) {
+        int opcode = _Py_OPCODE(instructions[i]);
+        switch (opcode) {
             case LOAD_FAST:
             case LOAD_FAST__LOAD_FAST:
             case LOAD_FAST__LOAD_CONST:
@@ -619,6 +620,7 @@ add_load_fast_null_checks(PyCodeObject *co)
                 _Py_SET_OPCODE(instructions[i], STORE_FAST);
                 break;
         }
+        i += _PyOpcode_Caches[_PyOpcode_Deopt[opcode]];
     }
     if (changed) {
         // invalidate cached co_code object