From 6d912e8b51886ec1a94378764c89b11fdf8bcbf8 Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <cxx@kayari.org>
Date: Thu, 26 Jan 2023 16:29:02 +0000
Subject: [PATCH] CP.44 improve example and add more accurate discussion
 (#2028)

---
 CppCoreGuidelines.md | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/CppCoreGuidelines.md b/CppCoreGuidelines.md
index 5925372..230a297 100644
--- a/CppCoreGuidelines.md
+++ b/CppCoreGuidelines.md
@@ -15184,15 +15184,26 @@ Flag "naked" `lock()` and `unlock()`.
 
 ##### Reason
 
-An unnamed local objects is a temporary that immediately goes out of scope.
+An unnamed local object is a temporary that immediately goes out of scope.
 
 ##### Example
 
-    unique_lock<mutex>(m1);
-    lock_guard<mutex> {m2};
-    lock(m1, m2);
+    // global mutexes
+    mutex m1;
+    mutex m2;
 
-This looks innocent enough, but it isn't.
+    void f()
+    {
+        unique_lock<mutex>(m1); // (A)
+        lock_guard<mutex> {m2}; // (B)
+        // do work in critical section ...
+    }
+
+This looks innocent enough, but it isn't. At (A), `m1` is a default-constructed
+local `unique_lock`, which shadows the global `::m1` (and does not lock it).
+At (B) an unnamed temporary `lock_guard` is constructed and locks `::m2`,
+but immediately goes out of scope and unlocks `::m2` again.
+For the rest of the function `f()` neither mutex is locked.
 
 ##### Enforcement