From 877210faa447f4cc7db87812f8ed80e398fedd61 Mon Sep 17 00:00:00 2001
From: Nathan Chancellor <nathan@kernel.org>
Date: Mon, 5 Jun 2023 10:49:41 -0700
Subject: [PATCH] [Sema] Do not emit -Wunused-variable for variables declared
 with cleanup attribute

A variable declared with __attribute__((cleanup)) cannot be unused, as
its address is passed to the clean up function. Do not emit
-Wunused-variable for variables declared with the cleanup attribute,
which matches GCC's behavior: https://godbolt.org/z/dz5YfTsan

Reviewed By: erichkeane, nickdesaulniers

Differential Revision: https://reviews.llvm.org/D152180
---
 clang/lib/Sema/SemaDecl.cpp             | 3 ++-
 clang/test/Sema/warn-unused-variables.c | 5 +++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index b8aba81..12fd378 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1992,7 +1992,8 @@ static bool ShouldDiagnoseUnusedDecl(const NamedDecl *D) {
     return false;
   }
 
-  if (D->hasAttr<UnusedAttr>() || D->hasAttr<ObjCPreciseLifetimeAttr>())
+  if (D->hasAttr<UnusedAttr>() || D->hasAttr<ObjCPreciseLifetimeAttr>() ||
+      D->hasAttr<CleanupAttr>())
     return false;
 
   if (isa<LabelDecl>(D))
diff --git a/clang/test/Sema/warn-unused-variables.c b/clang/test/Sema/warn-unused-variables.c
index d482c35..26b1872 100644
--- a/clang/test/Sema/warn-unused-variables.c
+++ b/clang/test/Sema/warn-unused-variables.c
@@ -30,3 +30,8 @@ int f3(void) {
   (void)(^() { int X = 4; }); // expected-warning{{unused}}
   (void)(^() { int X = 4; return Y + X; }); // expected-error {{use of undeclared identifier 'Y'}}
 }
+
+void c1(int *);
+void f4(void) {
+  int __attribute__((cleanup(c1))) X1 = 4;
+}
-- 
2.7.4