From e13796b885785c2e7a44dc1f8fedf13fa3a39c80 Mon Sep 17 00:00:00 2001
From: Vassil Vassilev <v.g.vassilev@gmail.com>
Date: Tue, 11 Apr 2017 10:13:54 +0000
Subject: [PATCH] Warn about unused static file scope function template
 declarations.

Reviewed by Richard Smith (D29877)!



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@299930 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/Sema.cpp                       | 14 ++++++++++++++
 lib/Sema/SemaDecl.cpp                   |  9 ++++-----
 test/SemaCXX/warn-unused-filescoped.cpp | 16 ++++++++++++++--
 3 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/lib/Sema/Sema.cpp b/lib/Sema/Sema.cpp
index 294b56059b3..f943ab56507 100644
--- a/lib/Sema/Sema.cpp
+++ b/lib/Sema/Sema.cpp
@@ -470,6 +470,13 @@ static bool ShouldRemoveFromUnused(Sema *SemaRef, const DeclaratorDecl *D) {
     return true;
 
   if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
+    // If this is a function template and none of its specializations is used,
+    // we should warn.
+    if (FunctionTemplateDecl *Template = FD->getDescribedFunctionTemplate())
+      for (const auto *Spec : Template->specializations())
+        if (ShouldRemoveFromUnused(SemaRef, Spec))
+          return true;
+
     // UnusedFileScopedDecls stores the first declaration.
     // The declaration may have become definition so check again.
     const FunctionDecl *DeclToCheck;
@@ -493,6 +500,13 @@ static bool ShouldRemoveFromUnused(Sema *SemaRef, const DeclaratorDecl *D) {
         VD->isUsableInConstantExpressions(SemaRef->Context))
       return true;
 
+    if (VarTemplateDecl *Template = VD->getDescribedVarTemplate())
+      // If this is a variable template and none of its specializations is used,
+      // we should warn.
+      for (const auto *Spec : Template->specializations())
+        if (ShouldRemoveFromUnused(SemaRef, Spec))
+          return true;
+
     // UnusedFileScopedDecls stores the first declaration.
     // The declaration may have become definition so check again.
     const VarDecl *DeclToCheck = VD->getDefinition();
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 02cbca8b2bb..20d1e0c6da6 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -8887,6 +8887,7 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
     if (FunctionTemplate) {
       if (NewFD->isInvalidDecl())
         FunctionTemplate->setInvalidDecl();
+      MarkUnusedFileScopedDecl(NewFD);
       return FunctionTemplate;
     }
   }
@@ -10987,8 +10988,7 @@ static bool hasDependentAlignment(VarDecl *VD) {
 
 /// FinalizeDeclaration - called by ParseDeclarationAfterDeclarator to perform
 /// any semantic actions necessary after any initializer has been attached.
-void
-Sema::FinalizeDeclaration(Decl *ThisDecl) {
+void Sema::FinalizeDeclaration(Decl *ThisDecl) {
   // Note that we are no longer parsing the initializer for this declaration.
   ParsingInitForAutoVars.erase(ThisDecl);
 
@@ -11153,9 +11153,8 @@ Sema::FinalizeDeclaration(Decl *ThisDecl) {
   if (DC->getRedeclContext()->isFileContext() && VD->isExternallyVisible())
     AddPushedVisibilityAttribute(VD);
 
-  // FIXME: Warn on unused templates.
-  if (VD->isFileVarDecl() && !VD->getDescribedVarTemplate() &&
-      !isa<VarTemplatePartialSpecializationDecl>(VD))
+  // FIXME: Warn on unused var template partial specializations.
+  if (VD->isFileVarDecl() && !isa<VarTemplatePartialSpecializationDecl>(VD))
     MarkUnusedFileScopedDecl(VD);
 
   // Now we have parsed the initializer and can update the table of magic
diff --git a/test/SemaCXX/warn-unused-filescoped.cpp b/test/SemaCXX/warn-unused-filescoped.cpp
index 18defee7d04..bd9335d3210 100644
--- a/test/SemaCXX/warn-unused-filescoped.cpp
+++ b/test/SemaCXX/warn-unused-filescoped.cpp
@@ -1,5 +1,5 @@
 // RUN: %clang_cc1 -fsyntax-only -verify -Wunused -Wunused-member-function -Wno-unused-local-typedefs -Wno-c++11-extensions -std=c++98 %s
-// RUN: %clang_cc1 -fsyntax-only -verify -Wunused -Wunused-member-function -Wno-unused-local-typedefs -std=c++11 %s
+// RUN: %clang_cc1 -fsyntax-only -verify -Wunused -Wunused-member-function -Wno-unused-local-typedefs -std=c++14 %s
 
 #ifdef HEADER
 
@@ -65,7 +65,7 @@ namespace {
   template <> void TS<int>::m() { }  // expected-warning{{unused}}
 
   template <typename T>
-  void tf() { }
+  void tf() { }  // expected-warning{{unused}}
   template <> void tf<int>() { }  // expected-warning{{unused}}
   
   struct VS {
@@ -200,6 +200,18 @@ void bar() { void func() __attribute__((used)); }
 static void func() {}
 }
 
+namespace test9 {
+template<typename T>
+static void completeRedeclChainForTemplateSpecialization() { } // expected-warning {{unused}}
+}
+
+namespace test10 {
+#if __cplusplus >= 201103L
+template<class T>
+constexpr T pi = T(3.14); // expected-warning {{unused}}
+#endif
+}
+
 namespace pr19713 {
 #if __cplusplus >= 201103L
   // FIXME: We should warn on both of these.
-- 
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