From 7b1fdbda2757cc4a7f25664475be44119d7f8e59 Mon Sep 17 00:00:00 2001
From: Ryan Flynn <pizza@parseerror.com>
Date: Fri, 31 Jul 2009 02:52:19 +0000
Subject: [PATCH] PR3679 - enable #pragma weak aliasing.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@77660 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/ParseAST.cpp     |  6 ++++++
 lib/Sema/Sema.h           | 13 ++++++++++++-
 lib/Sema/SemaDecl.cpp     |  2 +-
 lib/Sema/SemaDeclAttr.cpp | 18 ++++++++++++------
 4 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/lib/Sema/ParseAST.cpp b/lib/Sema/ParseAST.cpp
index 7fa8c595ee..a731401dcd 100644
--- a/lib/Sema/ParseAST.cpp
+++ b/lib/Sema/ParseAST.cpp
@@ -68,6 +68,12 @@ void clang::ParseAST(Preprocessor &PP, ASTConsumer *Consumer,
       Consumer->HandleTopLevelDecl(ADecl.getAsVal<DeclGroupRef>());
   };
   
+  // process any TopLevelDecls generated by #pragma weak
+  for (llvm::SmallVector<Decl*,2>::iterator
+        I = S.WeakTopLevelDecls().begin(),
+        E = S.WeakTopLevelDecls().end(); I != E; ++I)
+    Consumer->HandleTopLevelDecl(DeclGroupRef(*I));
+
   Consumer->HandleTranslationUnit(Ctx);
 
   if (PrintStats) {
diff --git a/lib/Sema/Sema.h b/lib/Sema/Sema.h
index e41172a0d5..dbf65782fb 100644
--- a/lib/Sema/Sema.h
+++ b/lib/Sema/Sema.h
@@ -254,6 +254,13 @@ public:
   };
   llvm::DenseMap<IdentifierInfo*,WeakInfo> WeakUndeclaredIdentifiers;
 
+  /// WeakTopLevelDecl - Translation-unit scoped declarations generated by
+  /// #pragma weak during processing of other Decls.
+  /// I couldn't figure out a clean way to generate these in-line, so
+  /// we store them here and handle separately -- which is a hack.
+  /// It would be best to refactor this.
+  llvm::SmallVector<Decl*,2> WeakTopLevelDecl;
+
   IdentifierResolver IdResolver;
 
   /// Translation Unit Scope - useful to Objective-C actions that need
@@ -381,6 +388,9 @@ public:
   llvm::SmallVector<SwitchStmt*,8> &getSwitchStack() {
     return CurBlock ? CurBlock->SwitchStack : FunctionSwitchStack;
   }
+
+  /// WeakTopLevelDeclDecls - access to #pragma weak-generated Decls
+  llvm::SmallVector<Decl*,2> &WeakTopLevelDecls() { return WeakTopLevelDecl; }
   
   virtual void ActOnComment(SourceRange Comment);
 
@@ -2948,7 +2958,8 @@ public:
                                  SourceLocation LParenLoc,
                                  SourceLocation RParenLoc);
 
-  void DeclApplyPragmaWeak(NamedDecl *D, WeakInfo &W);
+  NamedDecl *DeclClonePragmaWeak(NamedDecl *ND, IdentifierInfo *II);
+  void DeclApplyPragmaWeak(Scope *S, NamedDecl *ND, WeakInfo &W);
 
   /// ActOnPragmaWeakID - Called on well formed #pragma weak ident.
   virtual void ActOnPragmaWeakID(IdentifierInfo* WeakName,
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 58df38b645..8ee798aaf7 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -5220,7 +5220,7 @@ void Sema::ActOnPragmaWeakAlias(IdentifierInfo* Name,
   if (PrevDecl) {
     if (!PrevDecl->hasAttr<AliasAttr>())
       if (NamedDecl *ND = dyn_cast<NamedDecl>(PrevDecl))
-        DeclApplyPragmaWeak(ND, W);
+        DeclApplyPragmaWeak(TUScope, ND, W);
   } else {
     (void)WeakUndeclaredIdentifiers.insert(
       std::pair<IdentifierInfo*,WeakInfo>(AliasName, W));
diff --git a/lib/Sema/SemaDeclAttr.cpp b/lib/Sema/SemaDeclAttr.cpp
index a8efc2497a..08b4910a4f 100644
--- a/lib/Sema/SemaDeclAttr.cpp
+++ b/lib/Sema/SemaDeclAttr.cpp
@@ -1820,8 +1820,9 @@ void Sema::ProcessDeclAttributeList(Scope *S, Decl *D, const AttributeList *Attr
 
 /// DeclClonePragmaWeak - clone existing decl (maybe definition),
 /// #pragma weak needs a non-definition decl and source may not have one
-static NamedDecl * DeclClonePragmaWeak(NamedDecl *ND, IdentifierInfo *II)
+NamedDecl * Sema::DeclClonePragmaWeak(NamedDecl *ND, IdentifierInfo *II)
 {
+  assert(isa<FunctionDecl>(ND) || isa<VarDecl>(ND));
   NamedDecl *NewD = 0;
   if (FunctionDecl *FD = dyn_cast<FunctionDecl>(ND)) {
     NewD = FunctionDecl::Create(FD->getASTContext(), FD->getDeclContext(),
@@ -1837,8 +1838,7 @@ static NamedDecl * DeclClonePragmaWeak(NamedDecl *ND, IdentifierInfo *II)
 
 /// DeclApplyPragmaWeak - A declaration (maybe definition) needs #pragma weak
 /// applied to it, possibly with an alias.
-void Sema::DeclApplyPragmaWeak(NamedDecl *ND, WeakInfo &W) {
-  assert(isa<FunctionDecl>(ND) || isa<VarDecl>(ND));
+void Sema::DeclApplyPragmaWeak(Scope *S, NamedDecl *ND, WeakInfo &W) {
   if (!W.getUsed()) { // only do this once
     W.setUsed(true);
     if (W.getAlias()) { // clone decl, impersonate __attribute(weak,alias(...))
@@ -1846,7 +1846,13 @@ void Sema::DeclApplyPragmaWeak(NamedDecl *ND, WeakInfo &W) {
       NamedDecl *NewD = DeclClonePragmaWeak(ND, W.getAlias());
       NewD->addAttr(::new (Context) AliasAttr(NDId->getName()));
       NewD->addAttr(::new (Context) WeakAttr());
-      ND->getDeclContext()->addDecl(NewD);
+      WeakTopLevelDecl.push_back(NewD);
+      // FIXME: "hideous" code from Sema::LazilyCreateBuiltin
+      // to insert Decl at TU scope, sorry.
+      DeclContext *SavedContext = CurContext;
+      CurContext = Context.getTranslationUnitDecl();
+      PushOnScopeChains(NewD, S);
+      CurContext = SavedContext;
     } else { // just add weak to existing
       ND->addAttr(::new (Context) WeakAttr());
     }
@@ -1862,8 +1868,8 @@ void Sema::ProcessDeclAttributes(Scope *S, Decl *D, const Declarator &PD) {
     if (ND->hasLinkage()) {
       WeakInfo W = WeakUndeclaredIdentifiers.lookup(ND->getIdentifier());
       if (W != WeakInfo()) {
-        // Declaration referenced by #pragma weak before it was declared
-        DeclApplyPragmaWeak(ND, W);
+        // Identifier referenced by #pragma weak before it was declared
+        DeclApplyPragmaWeak(S, ND, W);
         WeakUndeclaredIdentifiers[ND->getIdentifier()] = W;
       }
     }
-- 
2.40.0