[PATCH] D152180: [Sema] Do not emit -Wunused-variable for variables declared with cleanup attribute

[Nathan Chancellor via Phabricator via cfe-commits]

nathanchance created this revision.
nathanchance added reviewers: aaron.ballman, nickdesaulniers, erichkeane.
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nathanchance requested review of this revision.
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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


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D152180

Files:
  clang/lib/Sema/SemaDecl.cpp
  clang/test/Sema/warn-unused-variables.c


Index: clang/test/Sema/warn-unused-variables.c
===================================================================
--- clang/test/Sema/warn-unused-variables.c
+++ clang/test/Sema/warn-unused-variables.c
@@ -30,3 +30,8 @@
   (void)(^() { int X = 4; }); // expected-warning{{unused}}
   (void)(^() { int X = 4; return Y + X; }); // expected-error {{use of 
undeclared identifier 'Y'}}
 }
+
+void c1(int *);
+int f4(void) {
+  int __attribute__((cleanup(c1))) X1 = 4;
+}
Index: clang/lib/Sema/SemaDecl.cpp
===================================================================
--- clang/lib/Sema/SemaDecl.cpp
+++ clang/lib/Sema/SemaDecl.cpp
@@ -1992,7 +1992,8 @@
     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))



Index: clang/test/Sema/warn-unused-variables.c
===================================================================
--- clang/test/Sema/warn-unused-variables.c
+++ clang/test/Sema/warn-unused-variables.c
@@ -30,3 +30,8 @@
   (void)(^() { int X = 4; }); // expected-warning{{unused}}
   (void)(^() { int X = 4; return Y + X; }); // expected-error {{use of undeclared identifier 'Y'}}
 }
+
+void c1(int *);
+int f4(void) {
+  int __attribute__((cleanup(c1))) X1 = 4;
+}
Index: clang/lib/Sema/SemaDecl.cpp
===================================================================
--- clang/lib/Sema/SemaDecl.cpp
+++ clang/lib/Sema/SemaDecl.cpp
@@ -1992,7 +1992,8 @@
     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))

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