In -Wunneeded-internal-declaration, suppress the warning for variables which

might have been used in constant expressions, rather than suppressing it for
variables which are const. The important thing here is that such variables
can have their values used without actually being marked as 'used'.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@166896 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 22 insertions, 2 deletions

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index e8d017c098..3576190310 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -1205,10 +1205,17 @@ bool Sema::ShouldWarnIfUnusedFileScopedDecl(const DeclaratorDecl *D) const {
       return false;
   } else if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
     if (!VD->isFileVarDecl() ||
-        VD->getType().isConstant(Context) ||
         Context.DeclMustBeEmitted(VD))
       return false;
 
+    // If a variable is usable in constant expressions and it's not odr-used,
+    // its value may still have been used. Conservatively suppress the warning
+    // in this case.
+    const VarDecl *VDWithInit = 0;
+    if (VD->isUsableInConstantExpressions(Context) &&
+        VD->getAnyInitializer(VDWithInit) && VDWithInit->checkInitIsICE())
+      return false;
+
     if (VD->isStaticDataMember() &&
         VD->getTemplateSpecializationKind() == TSK_ImplicitInstantiation)
       return false;
diff --git a/test/SemaCXX/warn-unused-filescoped.cpp b/test/SemaCXX/warn-unused-filescoped.cpp
index dbff4b0e68..328d8bbb5b 100644
--- a/test/SemaCXX/warn-unused-filescoped.cpp
+++ b/test/SemaCXX/warn-unused-filescoped.cpp
@@ -1,4 +1,5 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -Wunused -Wunused-member-function %s
+// RUN: %clang_cc1 -fsyntax-only -verify -Wunused -Wunused-member-function -std=c++98 %s
+// RUN: %clang_cc1 -fsyntax-only -verify -Wunused -Wunused-member-function -std=c++11 %s
 
 static void f1(); // expected-warning{{unused}}
 
@@ -87,3 +88,15 @@ namespace rdar8733476 {
     foo();
   }
 }
+
+namespace test5 {
+  static int n = 0;
+  static int &r = n;
+  int f(int &);
+  int k = f(r);
+
+  static const int m = n; // expected-warning {{not needed and will not be emitted}}
+  int x = sizeof(m);
+  static const double d = 0.0; // expected-warning {{not needed and will not be emitted}}
+  int y = sizeof(d);
+}