From: David Blaikie <dblaikie@gmail.com>
Date: Fri, 9 Dec 2011 18:32:50 +0000 (+0000)
Subject: Provide a separate warning for weak vtables in explicit template instantiations.... 
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=44d95b55711bc5c2e4055ebf1b5156e7fd3f0196;p=clang

Provide a separate warning for weak vtables in explicit template instantiations. There's no (current) way to fix such templates to emit strong symbols/vtables, but perhaps users want to know about the cost being incurred anyway.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@146265 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 2031d068a3..15824849e7 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -701,6 +701,10 @@ def warn_weak_vtable : Warning<
   "%0 has no out-of-line virtual method definitions; its vtable will be "
   "emitted in every translation unit">,
   InGroup<DiagGroup<"weak-vtables">>, DefaultIgnore;
+def warn_weak_template_vtable : Warning<
+  "explicit template instantiation %0 will emit a vtable in every "
+  "translation unit">,
+  InGroup<DiagGroup<"weak-template-vtables">>, DefaultIgnore;
 
 def ext_using_undefined_std : ExtWarn<
   "using directive refers to implicitly-defined namespace 'std'">;
diff --git a/lib/Sema/SemaDeclCXX.cpp b/lib/Sema/SemaDeclCXX.cpp
index 59c5e7894f..50e07553a1 100644
--- a/lib/Sema/SemaDeclCXX.cpp
+++ b/lib/Sema/SemaDeclCXX.cpp
@@ -10617,7 +10617,10 @@ bool Sema::DefineUsedVTables() {
       if (!KeyFunction || 
           (KeyFunction->hasBody(KeyFunctionDef) && 
            KeyFunctionDef->isInlined()))
-        Diag(Class->getLocation(), diag::warn_weak_vtable) << Class;
+        Diag(Class->getLocation(), Class->getTemplateSpecializationKind() ==
+             TSK_ExplicitInstantiationDefinition 
+             ? diag::warn_weak_template_vtable : diag::warn_weak_vtable) 
+          << Class;
     }
   }
   VTableUses.clear();
diff --git a/test/SemaCXX/warn-weak-vtables.cpp b/test/SemaCXX/warn-weak-vtables.cpp
index 912622f5a7..135e034259 100644
--- a/test/SemaCXX/warn-weak-vtables.cpp
+++ b/test/SemaCXX/warn-weak-vtables.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 %s -fsyntax-only -verify -Wweak-vtables
+// RUN: %clang_cc1 %s -fsyntax-only -verify -Wweak-vtables -Wweak-template-vtables
 
 struct A { // expected-warning {{'A' has no out-of-line virtual method definitions; its vtable will be emitted in every translation unit}}
   virtual void f() { } 
@@ -56,3 +56,23 @@ void uses(Parent &p, Derived &d, VeryDerived &vd) {
   d.getFoo();
   vd.getFoo();
 }
+
+template<typename T> struct TemplVirt {
+  virtual void f();
+};
+
+template class TemplVirt<float>; // expected-warning{{explicit template instantiation 'TemplVirt<float>' will emit a vtable in every translation unit}}
+
+template<> struct TemplVirt<bool> {
+  virtual void f();
+};
+
+template<> struct TemplVirt<long> { // expected-warning{{'TemplVirt<long>' has no out-of-line virtual method definitions; its vtable will be emitted in every translation unit}}
+  virtual void f() {}
+};
+
+void uses(TemplVirt<float>& f, TemplVirt<bool>& b, TemplVirt<long>& l) {
+  f.f();
+  b.f();
+  l.f();
+}