From 5028a2e1183fb3c8193e77242c517a745d1b4f58 Mon Sep 17 00:00:00 2001
From: Mark Shannon <mark@hotpy.org>
Date: Tue, 5 Jan 2021 11:05:40 +0000
Subject: [PATCH] Clarify logic about what instructions to line trace.

---
 Python/ceval.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/Python/ceval.c b/Python/ceval.c
index 58ccf13521b..609215623b9 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -5000,8 +5000,11 @@ maybe_call_line_trace(Py_tracefunc func, PyObject *obj,
     */
     int lastline = bounds->ar_line;
     int line = _PyCode_CheckLineNumber(frame->f_lasti, bounds);
-    if (frame->f_lasti < *instr_prev || (line != lastline && frame->f_lasti == bounds->ar_start)) {
-        if (line != -1 && frame->f_trace_lines) {
+    if (line != -1 && frame->f_trace_lines) {
+        /* Trace backward edges or first instruction of a new line */
+        if (frame->f_lasti < *instr_prev ||
+            (line != lastline && frame->f_lasti == bounds->ar_start))
+        {
             frame->f_lineno = line;
             result = call_trace(func, obj, tstate, frame, PyTrace_LINE, Py_None);
             frame->f_lineno = 0;