Progress towards making isUsed() reflect whether a declaration is odr-used; don't set isUsed for local variables which are referenced in unevaluated contexts. Make other code use isReferenced() (which basically indicates that a declaration isn't dead) where appropriate.

I was forced to change test/SemaCXX/linkage.cpp because we aren't actually modeling extern "C" in the AST the way that testcase expects; we were not printing a warning only because we skipped the relevant check.  Someone who actually understands the semantics here should fix that.

llvm-svn: 148158

2 files changed, 2 insertions, 12 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 20309ee51cc..37cb9c9a70e 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1095,7 +1095,7 @@ static bool ShouldDiagnoseUnusedDecl(const NamedDecl *D) {
   if (D->isInvalidDecl())
     return false;
 
-  if (D->isUsed() || D->hasAttr<UnusedAttr>())
+  if (D->isReferenced() || D->isUsed() || D->hasAttr<UnusedAttr>())
     return false;
 
   if (isa<LabelDecl>(D))
@@ -6804,7 +6804,7 @@ void Sema::DiagnoseUnusedParameters(ParmVarDecl * const *Param,
     return;
 
   for (; Param != ParamEnd; ++Param) {
-    if (!(*Param)->isUsed() && (*Param)->getDeclName() &&
+    if (!(*Param)->isReferenced() && (*Param)->getDeclName() &&
         !(*Param)->hasAttr<UnusedAttr>()) {
       Diag((*Param)->getLocation(), diag::warn_unused_parameter)
         << (*Param)->getDeclName();
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 8625d9b2601..15f56e840c5 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -9377,16 +9377,6 @@ void Sema::MarkDeclarationReferenced(SourceLocation Loc, Decl *D) {
   if (D->isUsed(false))
     return;
 
-  // Mark a parameter or variable declaration "used", regardless of whether
-  // we're in a template or not. The reason for this is that unevaluated
-  // expressions (e.g. (void)sizeof()) constitute a use for warning purposes
-  // (-Wunused-variables and -Wunused-parameters)
-  if (isa<ParmVarDecl>(D) ||
-      (isa<VarDecl>(D) && D->getDeclContext()->isFunctionOrMethod())) {
-    D->setUsed();
-    return;
-  }
-
   if (!isa<VarDecl>(D) && !isa<FunctionDecl>(D))
     return;