r316096 - Enable support for the [[maybe_unused]] attribute from WG14 N2053 when enabling double square bracket attributes in C code.

[Aaron Ballman via cfe-commits]

Author: aaronballman
Date: Wed Oct 18 09:59:27 2017
New Revision: 316096

URL: http://llvm.org/viewvc/llvm-project?rev=316096&view=rev
Log:
Enable support for the [[maybe_unused]] attribute from WG14 N2053 when enabling double square bracket attributes in C code.

Added:
    cfe/trunk/test/Sema/c2x-maybe_unused-errors.c
    cfe/trunk/test/Sema/c2x-maybe_unused.c
Modified:
    cfe/trunk/include/clang/Basic/Attr.td
    cfe/trunk/lib/Sema/SemaExpr.cpp

Modified: cfe/trunk/include/clang/Basic/Attr.td
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/Attr.td?rev=316096&r1=316095&r2=316096&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/Attr.td (original)
+++ cfe/trunk/include/clang/Basic/Attr.td Wed Oct 18 09:59:27 2017
@@ -1936,7 +1936,8 @@ def ObjCRequiresPropertyDefs : Inheritab
 }
 
 def Unused : InheritableAttr {
-  let Spellings = [CXX11<"", "maybe_unused", 201603>, GCC<"unused">];
+  let Spellings = [CXX11<"", "maybe_unused", 201603>, GCC<"unused">,
+                   C2x<"", "maybe_unused">];
   let Subjects = SubjectList<[Var, ObjCIvar, Type, Enum, EnumConstant, Label,
                               Field, ObjCMethod, FunctionLike], WarnDiag,
                              "ExpectedForMaybeUnused">;

Modified: cfe/trunk/lib/Sema/SemaExpr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=316096&r1=316095&r2=316096&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
+++ cfe/trunk/lib/Sema/SemaExpr.cpp Wed Oct 18 09:59:27 2017
@@ -79,7 +79,8 @@ static void DiagnoseUnusedOfDecl(Sema &S
   if (const auto *A = D->getAttr<UnusedAttr>()) {
     // [[maybe_unused]] should not diagnose uses, but __attribute__((unused))
     // should diagnose them.
-    if (A->getSemanticSpelling() != UnusedAttr::CXX11_maybe_unused) {
+    if (A->getSemanticSpelling() != UnusedAttr::CXX11_maybe_unused &&
+        A->getSemanticSpelling() != UnusedAttr::C2x_maybe_unused) {
       const Decl *DC = cast_or_null<Decl>(S.getCurObjCLexicalContext());
       if (DC && !DC->hasAttr<UnusedAttr>())
         S.Diag(Loc, diag::warn_used_but_marked_unused) << D->getDeclName();

Added: cfe/trunk/test/Sema/c2x-maybe_unused-errors.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/c2x-maybe_unused-errors.c?rev=316096&view=auto
==============================================================================
--- cfe/trunk/test/Sema/c2x-maybe_unused-errors.c (added)
+++ cfe/trunk/test/Sema/c2x-maybe_unused-errors.c Wed Oct 18 09:59:27 2017
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -fsyntax-only -Wunused -fdouble-square-bracket-attributes -verify %s
+
+struct [[maybe_unused]] S1 { // ok
+  int a [[maybe_unused]];
+};
+struct [[maybe_unused maybe_unused]] S2 { // expected-error {{attribute 'maybe_unused' cannot appear multiple times in an attribute specifier}}
+  int a;
+};
+struct [[maybe_unused("Wrong")]] S3 { // expected-error {{'maybe_unused' cannot have an argument list}}
+  int a;
+};
+

Added: cfe/trunk/test/Sema/c2x-maybe_unused.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/c2x-maybe_unused.c?rev=316096&view=auto
==============================================================================
--- cfe/trunk/test/Sema/c2x-maybe_unused.c (added)
+++ cfe/trunk/test/Sema/c2x-maybe_unused.c Wed Oct 18 09:59:27 2017
@@ -0,0 +1,35 @@
+// RUN: %clang_cc1 -fsyntax-only -Wunused -fdouble-square-bracket-attributes -verify %s
+
+struct [[maybe_unused]] S1 { // ok
+  int a [[maybe_unused]];
+};
+
+enum [[maybe_unused]] E1 {
+  EnumVal [[maybe_unused]]
+};
+
+[[maybe_unused]] void unused_func([[maybe_unused]] int parm) {
+  typedef int maybe_unused_int [[maybe_unused]];
+  [[maybe_unused]] int I;
+}
+
+void f1(void) {
+  int x; // expected-warning {{unused variable}}
+  typedef int I; // expected-warning {{unused typedef 'I'}}
+
+  // Should not warn about these due to not being used.
+  [[maybe_unused]] int y;
+  typedef int maybe_unused_int [[maybe_unused]];
+
+  // Should not warn about these uses.
+  struct S1 s;
+  maybe_unused_int test;
+  y = 12;
+}
+
+void f2(void);
+[[maybe_unused]] void f2(void);
+
+void f2(void) {
+}
+