[libcxx-commits] [clang] [libcxx] [clang][ThreadSafety] Handle mutex scope (PR #157171)

[Prabhu Rajasekaran via libcxx-commits]

https://github.com/Prabhuk updated https://github.com/llvm/llvm-project/pull/157171

>From e6af544156940a1041a01a44d73dae76ac322111 Mon Sep 17 00:00:00 2001
From: prabhukr <prabhukr at google.com>
Date: Fri, 5 Sep 2025 13:35:10 -0700
Subject: [PATCH] [clang][ThreadSafety] Handle mutex scope

Before emitting warning about locks being held at the end of function
scope check if the underlying mutex is function scoped or not.
---
 clang/lib/Analysis/ThreadSafety.cpp              | 16 ++++++++++++++++
 .../clang/thread/thread.mutex/lock.verify.cpp    |  6 ++++++
 2 files changed, 22 insertions(+)

diff --git a/clang/lib/Analysis/ThreadSafety.cpp b/clang/lib/Analysis/ThreadSafety.cpp
index 131170df9976e..b215a6e6d74cc 100644
--- a/clang/lib/Analysis/ThreadSafety.cpp
+++ b/clang/lib/Analysis/ThreadSafety.cpp
@@ -2443,6 +2443,22 @@ void ThreadSafetyAnalyzer::intersectAndWarn(FactSet &EntrySet,
       if (join(FactMan[*EntryIt], ExitFact, JoinLoc, EntryLEK))
         *EntryIt = Fact;
     } else if (!ExitFact.managed() || EntryLEK == LEK_LockedAtEndOfFunction) {
+      if (EntryLEK == LEK_LockedAtEndOfFunction) {
+        const til::SExpr *Sexp = ExitFact.sexpr();
+        const VarDecl *Var = nullptr;
+
+        if (const auto *Proj = dyn_cast<til::Project>(Sexp)) {
+          if (const auto *Base = dyn_cast<til::LiteralPtr>(Proj->record()))
+            Var = dyn_cast_or_null<VarDecl>(Base->clangDecl());
+        } else if (const auto *LP = dyn_cast<til::LiteralPtr>(Sexp)) {
+          Var = dyn_cast_or_null<VarDecl>(LP->clangDecl());
+        }
+
+        if (Var && Var->getStorageDuration() == SD_Automatic &&
+            Var->getDeclContext() == CurrentFunction) {
+          continue;
+        }
+      }
       ExitFact.handleRemovalFromIntersection(ExitSet, FactMan, JoinLoc,
                                              EntryLEK, Handler);
     }
diff --git a/libcxx/test/extensions/clang/thread/thread.mutex/lock.verify.cpp b/libcxx/test/extensions/clang/thread/thread.mutex/lock.verify.cpp
index 51ffa6962ac83..e0d4ec39ea845 100644
--- a/libcxx/test/extensions/clang/thread/thread.mutex/lock.verify.cpp
+++ b/libcxx/test/extensions/clang/thread/thread.mutex/lock.verify.cpp
@@ -45,3 +45,9 @@ void f3() {
      expected-warning {{mutex 'm2' is still held at the end of function}} \
      expected-warning {{mutex 'm3' is still held at the end of function}}
 #endif
+
+void f4() {
+  std::mutex local_m0;
+  std::mutex local_m1;
+  std::lock(local_m0, local_m1);
+}