commit 5764f613e61cb3183f3d7ceeafd23396de96ed16
author Douglas Gregor <dgregor@apple.com> Sat May 08 23:05:03 2010 +0000
committer Douglas Gregor <dgregor@apple.com> Sat May 08 23:05:03 2010 +0000
tree 75c809eafa8232c6f8baec88596392cf718d7a5e
parent c6dfe194f623b02c123759f235b504d4850fc178

Improve our handling of the -Wunused-variable warning in templates. In
particular, don't complain about unused variables that have dependent
type until instantiation time, so that we can look at the type of the
variable. Moreover, only complain about unused variables that have
neither a user-declared constructor nor a non-trivial destructor.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@103362 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Sema/Sema.h

diff --git a/lib/Sema/Sema.h b/lib/Sema/Sema.h
index 24480fe..3bea485 100644
--- a/lib/Sema/Sema.h
+++ b/lib/Sema/Sema.h
@@ -1761,7 +1761,8 @@
   /// DiagnoseUnusedExprResult - If the statement passed in is an expression
   /// whose result is unused, warn.
   void DiagnoseUnusedExprResult(const Stmt *S);
-
+  void DiagnoseUnusedDecl(const NamedDecl *ND);
+  
   ParsingDeclStackState PushParsingDeclaration();
   void PopParsingDeclaration(ParsingDeclStackState S, DeclPtrTy D);
   void EmitDeprecationWarning(NamedDecl *D, SourceLocation Loc);

lib/Sema/SemaDecl.cpp

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index bf3c172..40ba8ff 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -544,9 +544,9 @@
         return false;
     }
 
-    // If we failed to complete the type for some reason, don't
-    // diagnose the variable.
-    if (Ty->isIncompleteType())
+    // If we failed to complete the type for some reason, or if the type is
+    // dependent, don't diagnose the variable. 
+    if (Ty->isIncompleteType() || Ty->isDependentType())
       return false;
 
     if (const TagType *TT = Ty->getAs<TagType>()) {
@@ -555,9 +555,10 @@
         return false;
 
       if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(Tag)) {
-        if (!RD->hasTrivialConstructor())
-          return false;
-        if (!RD->hasTrivialDestructor())
+        // FIXME: Checking for the presence of a user-declared constructor
+        // isn't completely accurate; we'd prefer to check that the initializer
+        // has no side effects.
+        if (RD->hasUserDeclaredConstructor() || !RD->hasTrivialDestructor())
           return false;
       }
     }
@@ -568,6 +569,18 @@
   return true;
 }
 
+void Sema::DiagnoseUnusedDecl(const NamedDecl *D) {
+  if (!ShouldDiagnoseUnusedDecl(D))
+    return;
+  
+  if (isa<VarDecl>(D) && cast<VarDecl>(D)->isExceptionVariable())
+    Diag(D->getLocation(), diag::warn_unused_exception_param)
+    << D->getDeclName();
+  else
+    Diag(D->getLocation(), diag::warn_unused_variable) 
+    << D->getDeclName();
+}
+
 void Sema::ActOnPopScope(SourceLocation Loc, Scope *S) {
   if (S->decl_empty()) return;
   assert((S->getFlags() & (Scope::DeclScope | Scope::TemplateParamScope)) &&
@@ -584,15 +597,9 @@
     if (!D->getDeclName()) continue;
 
     // Diagnose unused variables in this scope.
-    if (ShouldDiagnoseUnusedDecl(D) && 
-        S->getNumErrorsAtStart() == getDiagnostics().getNumErrors()) {
-      if (isa<VarDecl>(D) && cast<VarDecl>(D)->isExceptionVariable())
-        Diag(D->getLocation(), diag::warn_unused_exception_param)
-          << D->getDeclName();
-      else
-        Diag(D->getLocation(), diag::warn_unused_variable) 
-          << D->getDeclName();
-    }
+    if (S->getNumErrorsAtStart() == getDiagnostics().getNumErrors())
+      DiagnoseUnusedDecl(D);
+    
     // Remove this name from our lexical scope.
     IdResolver.RemoveDecl(D);
   }

lib/Sema/SemaTemplateInstantiateDecl.cpp

diff --git a/lib/Sema/SemaTemplateInstantiateDecl.cpp b/lib/Sema/SemaTemplateInstantiateDecl.cpp
index a32c0e1..d3d6c22 100644
--- a/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -351,7 +351,8 @@
     Var->setLexicalDeclContext(D->getLexicalDeclContext());
 
   Var->setAccess(D->getAccess());
-
+  Var->setUsed(D->isUsed());
+  
   // FIXME: In theory, we could have a previous declaration for variables that
   // are not static data members.
   bool Redeclaration = false;
@@ -419,6 +420,10 @@
   } else if (!Var->isStaticDataMember() || Var->isOutOfLine())
     SemaRef.ActOnUninitializedDecl(Sema::DeclPtrTy::make(Var), false);
 
+  // Diagnose unused local variables.
+  if (!Var->isInvalidDecl() && Owner->isFunctionOrMethod() && !Var->isUsed())
+    SemaRef.DiagnoseUnusedDecl(Var);
+  
   return Var;
 }