From f1d2f0ea21a5a66864da5cd8d39404df5b3fd652 Mon Sep 17 00:00:00 2001
From: Rafael Espindola <rafael.espindola@gmail.com>
Date: Wed, 16 Jan 2013 23:11:15 +0000
Subject: [PATCH] Check for internal weak decls after merging.

This fixes pr14946. The problem was that the linkage computation was done too
early, so things like "extern int a;" would be given external linkage, even if
a previous declaration was static.

llvm-svn: 172667
---
 clang/lib/Sema/SemaDecl.cpp      | 13 +++++++++++++
 clang/lib/Sema/SemaDeclAttr.cpp  |  6 ------
 clang/test/Sema/attr-weak.c      |  6 ++++++
 clang/test/SemaCXX/attr-weak.cpp |  7 +++++++
 4 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 994b212..0316654 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -4312,6 +4312,15 @@ bool Sema::inferObjCARCLifetime(ValueDecl *decl) {
   return false;
 }
 
+static void checkAttributesAfterMerging(Sema &S, NamedDecl &ND) {
+  // 'weak' only applies to declarations with external linkage.
+  WeakAttr *WA = ND.getAttr<WeakAttr>();
+  if (WA && ND.getLinkage() != ExternalLinkage) {
+    S.Diag(WA->getLocation(), diag::err_attribute_weak_static);
+    ND.dropAttr<WeakAttr>();
+  }
+}
+
 NamedDecl*
 Sema::ActOnVariableDeclarator(Scope *S, Declarator &D, DeclContext *DC,
                               TypeSourceInfo *TInfo, LookupResult &Previous,
@@ -4590,6 +4599,8 @@ Sema::ActOnVariableDeclarator(Scope *S, Declarator &D, DeclContext *DC,
       NewVD->setInvalidDecl();
   }
 
+  checkAttributesAfterMerging(*this, *NewVD);
+
   // If this is a locally-scoped extern C variable, update the map of
   // such variables.
   if (CurContext->isFunctionOrMethod() && NewVD->isExternC() &&
@@ -6056,6 +6067,8 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
     }
   }
 
+  checkAttributesAfterMerging(*this, *NewFD);
+
   AddKnownFunctionAttributes(NewFD);
 
   if (NewFD->hasAttr<OverloadableAttr>() && 
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index 85f48ec..efeafa6 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -2511,12 +2511,6 @@ static void handleWeakAttr(Sema &S, Decl *D, const AttributeList &Attr) {
 
   NamedDecl *nd = cast<NamedDecl>(D);
 
-  // 'weak' only applies to declarations with external linkage.
-  if (hasEffectivelyInternalLinkage(nd)) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_weak_static);
-    return;
-  }
-
   nd->addAttr(::new (S.Context) WeakAttr(Attr.getRange(), S.Context));
 }
 
diff --git a/clang/test/Sema/attr-weak.c b/clang/test/Sema/attr-weak.c
index adedf12..df74554 100644
--- a/clang/test/Sema/attr-weak.c
+++ b/clang/test/Sema/attr-weak.c
@@ -16,3 +16,9 @@ static int x __attribute__((weak)); // expected-error {{weak declaration cannot
 // rdar://9538608
 int C; // expected-note {{previous definition is here}}
 extern int C __attribute__((weak_import)); // expected-warning {{an already-declared variable is made a weak_import declaration}}
+
+static int pr14946_x;
+extern int pr14946_x  __attribute__((weak)); // expected-error {{weak declaration cannot have internal linkage}}
+
+static void pr14946_f();
+void pr14946_f() __attribute__((weak)); // expected-error {{weak declaration cannot have internal linkage}}
diff --git a/clang/test/SemaCXX/attr-weak.cpp b/clang/test/SemaCXX/attr-weak.cpp
index b6a9e0a..8939a28 100644
--- a/clang/test/SemaCXX/attr-weak.cpp
+++ b/clang/test/SemaCXX/attr-weak.cpp
@@ -21,9 +21,16 @@ namespace {
   };
 }
 
+// GCC rejects the instantiation with the internal type, but some existing
+// code expects it. It is also not that different from giving hidden visibility
+// to parts of a template that have explicit default visibility, so we accept
+// this.
 template <class T> struct Test7 {
   void test7() __attribute__((weak)) {}
+  static int var __attribute__((weak));
 };
+template <class T>
+int Test7<T>::var;
 namespace { class Internal; }
 template struct Test7<Internal>;
 template struct Test7<int>;
-- 
2.7.4