From: Ken Jin <kenjin@python.org>
Date: Mon, 27 Oct 2025 18:26:47 +0000 (+0800)
Subject: gh-140104: Set next_instr properly in the JIT during exceptions (GH-140233)
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=a7160912274003672dc116d918260c0a81551c21;p=thirdparty%2FPython%2Fcpython.git

gh-140104: Set next_instr properly in the JIT during exceptions (GH-140233)



Co-authored-by: devdanzin <74280297+devdanzin@users.noreply.github.com>
Co-authored-by: Chris Eibl <138194463+chris-eibl@users.noreply.github.com>
---

diff --git a/Lib/test/test_capi/test_opt.py b/Lib/test/test_capi/test_opt.py
index f121f2717487..4e94f62d35eb 100644
--- a/Lib/test/test_capi/test_opt.py
+++ b/Lib/test/test_capi/test_opt.py
@@ -2637,6 +2637,30 @@ class TestUopsOptimization(unittest.TestCase):
 
         f2()
 
+    def test_next_instr_for_exception_handler_set(self):
+        # gh-140104: We just want the exception to be caught properly.
+        def f():
+            for i in range(TIER2_THRESHOLD + 3):
+                try:
+                    undefined_variable(i)
+                except Exception:
+                    pass
+
+        f()
+
+    def test_next_instr_for_exception_handler_set_lasts_instr(self):
+        # gh-140104: We just want the exception to be caught properly.
+        def f():
+            a_list = []
+            for _ in range(TIER2_THRESHOLD + 3):
+                try:
+                    a_list[""] = 0
+                except Exception:
+                    pass
+
+        f()
+
+
 
 def global_identity(x):
     return x
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-10-16-21-47-00.gh-issue-140104.A8SQIm.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-10-16-21-47-00.gh-issue-140104.A8SQIm.rst
new file mode 100644
index 000000000000..1c18cbc9ad05
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-10-16-21-47-00.gh-issue-140104.A8SQIm.rst
@@ -0,0 +1,2 @@
+Fix a bug with exception handling in the JIT. Patch by Ken Jin. Bug reported
+by Daniel Diniz.
diff --git a/Python/ceval_macros.h b/Python/ceval_macros.h
index 4ed03b7fb01b..8083913b1a1c 100644
--- a/Python/ceval_macros.h
+++ b/Python/ceval_macros.h
@@ -358,7 +358,9 @@ do {                                                   \
     frame = tstate->current_frame;                     \
     stack_pointer = _PyFrame_GetStackPointer(frame);   \
     if (next_instr == NULL) {                          \
-        next_instr = frame->instr_ptr;                 \
+        /* gh-140104: The exception handler expects frame->instr_ptr
+            to after this_instr, not this_instr! */ \
+        next_instr = frame->instr_ptr + 1;                 \
         JUMP_TO_LABEL(error);                          \
     }                                                  \
     DISPATCH();                                        \