GH-95113: Don't use EXTENDED_ARG_QUICK in unquickened code (GH-95121)

1 files changed, 8 insertions, 0 deletions

diff --git a/Python/ceval.c b/Python/ceval.c
index 88d13c8..3a9b0e5 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -5631,8 +5631,16 @@ handle_eval_breaker:
             assert(oparg);
             oparg <<= 8;
             oparg |= _Py_OPARG(*next_instr);
+            // We might be tracing. To avoid breaking tracing guarantees in 
+            // quickened instructions, always deoptimize the next opcode:
             opcode = _PyOpcode_Deopt[_Py_OPCODE(*next_instr)];
             PRE_DISPATCH_GOTO();
+            // CPython hasn't traced the following instruction historically
+            // (DO_TRACING would clobber our extended oparg anyways), so just
+            // skip our usual cframe.use_tracing check before dispatch. Also,
+            // make sure the next instruction isn't a RESUME, since that needs
+            // to trace properly (and shouldn't have an extended arg anyways):
+            assert(opcode != RESUME);
             DISPATCH_GOTO();
         }