SemaDecl.cpp

//===--- SemaDecl.cpp - Semantic Analysis for Declarations ----------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//  This file implements semantic analysis for declarations.
//
//===----------------------------------------------------------------------===//

#include "Sema.h"
#include "clang/AST/APValue.h"
#include "clang/AST/ASTConsumer.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/ExprCXX.h"
#include "clang/Parse/DeclSpec.h"
#include "clang/Basic/Diagnostic.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Basic/SourceManager.h"
// FIXME: layering (ideally, Sema shouldn't be dependent on Lex API's)
#include "clang/Lex/Preprocessor.h"
#include "clang/Lex/HeaderSearch.h" 
#include "llvm/ADT/SmallSet.h"
using namespace clang;

Sema::TypeTy *Sema::isTypeName(const IdentifierInfo &II, Scope *S) {
  Decl *IIDecl = LookupDecl(&II, Decl::IDNS_Ordinary, S, false);

  if (IIDecl && (isa<TypedefDecl>(IIDecl) || 
                 isa<ObjCInterfaceDecl>(IIDecl) ||
                 isa<TagDecl>(IIDecl)))
    return IIDecl;
  return 0;
}

DeclContext *Sema::getDCParent(DeclContext *DC) {
  // If CurContext is a ObjC method, getParent() will return NULL.
  if (isa<ObjCMethodDecl>(DC))
    return Context.getTranslationUnitDecl();

  // A C++ inline method is parsed *after* the topmost class it was declared in
  // is fully parsed (it's "complete").
  // The parsing of a C++ inline method happens at the declaration context of
  // the topmost (non-nested) class it is declared in.
  if (CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(DC)) {
    assert(isa<CXXRecordDecl>(MD->getParent()) && "C++ method not in Record.");
    DC = MD->getParent();
    while (CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(DC->getParent()))
      DC = RD;

    // Return the declaration context of the topmost class the inline method is
    // declared in.
    return DC;
  }

  return DC->getParent();
}

void Sema::PushDeclContext(DeclContext *DC) {
  assert(getDCParent(DC) == CurContext &&
       "The next DeclContext should be directly contained in the current one.");
  CurContext = DC;
}

void Sema::PopDeclContext() {
  assert(CurContext && "DeclContext imbalance!");
  CurContext = getDCParent(CurContext);
}

/// Add this decl to the scope shadowed decl chains.
void Sema::PushOnScopeChains(NamedDecl *D, Scope *S) {
  S->AddDecl(D);

  // C++ [basic.scope]p4:
  //   -- exactly one declaration shall declare a class name or
  //   enumeration name that is not a typedef name and the other
  //   declarations shall all refer to the same object or
  //   enumerator, or all refer to functions and function templates;
  //   in this case the class name or enumeration name is hidden.
  if (TagDecl *TD = dyn_cast<TagDecl>(D)) {
    // We are pushing the name of a tag (enum or class).
    IdentifierResolver::iterator
        I = IdResolver.begin(TD->getIdentifier(),
                             TD->getDeclContext(), false/*LookInParentCtx*/);
    if (I != IdResolver.end() && isDeclInScope(*I, TD->getDeclContext(), S)) {
      // There is already a declaration with the same name in the same
      // scope. It must be found before we find the new declaration,
      // so swap the order on the shadowed declaration chain.

      IdResolver.AddShadowedDecl(TD, *I);
      return;
    }
  }
  IdResolver.AddDecl(D);
}

void Sema::ActOnPopScope(SourceLocation Loc, Scope *S) {
  if (S->decl_empty()) return;
  assert((S->getFlags() & Scope::DeclScope) &&"Scope shouldn't contain decls!");

  for (Scope::decl_iterator I = S->decl_begin(), E = S->decl_end();
       I != E; ++I) {
    Decl *TmpD = static_cast<Decl*>(*I);
    assert(TmpD && "This decl didn't get pushed??");

    if (isa<CXXFieldDecl>(TmpD)) continue;

    assert(isa<ScopedDecl>(TmpD) && "Decl isn't ScopedDecl?");
    ScopedDecl *D = cast<ScopedDecl>(TmpD);
    
    IdentifierInfo *II = D->getIdentifier();
    if (!II) continue;
    
    // We only want to remove the decls from the identifier decl chains for
    // local scopes, when inside a function/method.
    if (S->getFnParent() != 0)
      IdResolver.RemoveDecl(D);

    // Chain this decl to the containing DeclContext.
    D->setNext(CurContext->getDeclChain());
    CurContext->setDeclChain(D);
  }
}

/// getObjCInterfaceDecl - Look up a for a class declaration in the scope.
/// return 0 if one not found.
ObjCInterfaceDecl *Sema::getObjCInterfaceDecl(IdentifierInfo *Id) {
  // The third "scope" argument is 0 since we aren't enabling lazy built-in
  // creation from this context.
  Decl *IDecl = LookupDecl(Id, Decl::IDNS_Ordinary, 0, false);
  
  return dyn_cast_or_null<ObjCInterfaceDecl>(IDecl);
}

/// LookupDecl - Look up the inner-most declaration in the specified
/// namespace.
Decl *Sema::LookupDecl(const IdentifierInfo *II, unsigned NSI,
                       Scope *S, bool enableLazyBuiltinCreation) {
  if (II == 0) return 0;
  unsigned NS = NSI;
  if (getLangOptions().CPlusPlus && (NS & Decl::IDNS_Ordinary))
    NS |= Decl::IDNS_Tag;

  // Scan up the scope chain looking for a decl that matches this identifier
  // that is in the appropriate namespace.  This search should not take long, as
  // shadowing of names is uncommon, and deep shadowing is extremely uncommon.
  for (IdentifierResolver::iterator
       I = IdResolver.begin(II, CurContext), E = IdResolver.end(); I != E; ++I)
    if ((*I)->getIdentifierNamespace() & NS)
      return *I;

  // If we didn't find a use of this identifier, and if the identifier
  // corresponds to a compiler builtin, create the decl object for the builtin
  // now, injecting it into translation unit scope, and return it.
  if (NS & Decl::IDNS_Ordinary) {
    if (enableLazyBuiltinCreation) {
      // If this is a builtin on this (or all) targets, create the decl.
      if (unsigned BuiltinID = II->getBuiltinID())
        return LazilyCreateBuiltin((IdentifierInfo *)II, BuiltinID, S);
    }
    if (getLangOptions().ObjC1) {
      // @interface and @compatibility_alias introduce typedef-like names.
      // Unlike typedef's, they can only be introduced at file-scope (and are 
      // therefore not scoped decls). They can, however, be shadowed by
      // other names in IDNS_Ordinary.
      ObjCInterfaceDeclsTy::iterator IDI = ObjCInterfaceDecls.find(II);
      if (IDI != ObjCInterfaceDecls.end())
        return IDI->second;
      ObjCAliasTy::iterator I = ObjCAliasDecls.find(II);
      if (I != ObjCAliasDecls.end())
        return I->second->getClassInterface();
    }
  }
  return 0;
}

void Sema::InitBuiltinVaListType() {
  if (!Context.getBuiltinVaListType().isNull())
    return;
  
  IdentifierInfo *VaIdent = &Context.Idents.get("__builtin_va_list");
  Decl *VaDecl = LookupDecl(VaIdent, Decl::IDNS_Ordinary, TUScope);
  TypedefDecl *VaTypedef = cast<TypedefDecl>(VaDecl);
  Context.setBuiltinVaListType(Context.getTypedefType(VaTypedef));
}

/// LazilyCreateBuiltin - The specified Builtin-ID was first used at file scope.
/// lazily create a decl for it.
ScopedDecl *Sema::LazilyCreateBuiltin(IdentifierInfo *II, unsigned bid,
                                      Scope *S) {
  Builtin::ID BID = (Builtin::ID)bid;

  if (Context.BuiltinInfo.hasVAListUse(BID))
    InitBuiltinVaListType();
    
  QualType R = Context.BuiltinInfo.GetBuiltinType(BID, Context);  
  FunctionDecl *New = FunctionDecl::Create(Context,
                                           Context.getTranslationUnitDecl(),
                                           SourceLocation(), II, R,
                                           FunctionDecl::Extern, false, 0);
  
  // Create Decl objects for each parameter, adding them to the
  // FunctionDecl.
  if (FunctionTypeProto *FT = dyn_cast<FunctionTypeProto>(R)) {
    llvm::SmallVector<ParmVarDecl*, 16> Params;
    for (unsigned i = 0, e = FT->getNumArgs(); i != e; ++i)
      Params.push_back(ParmVarDecl::Create(Context, New, SourceLocation(), 0,
                                           FT->getArgType(i), VarDecl::None, 0,
                                           0));
    New->setParams(&Params[0], Params.size());
  }
  
  
  
  // TUScope is the translation-unit scope to insert this function into.
  PushOnScopeChains(New, TUScope);
  return New;
}

/// MergeTypeDefDecl - We just parsed a typedef 'New' which has the same name
/// and scope as a previous declaration 'Old'.  Figure out how to resolve this
/// situation, merging decls or emitting diagnostics as appropriate.
///
TypedefDecl *Sema::MergeTypeDefDecl(TypedefDecl *New, Decl *OldD) {
  // Allow multiple definitions for ObjC built-in typedefs.
  // FIXME: Verify the underlying types are equivalent!
  if (getLangOptions().ObjC1) {
    const IdentifierInfo *typeIdent = New->getIdentifier();
    if (typeIdent == Ident_id) {
      Context.setObjCIdType(New);
      return New;
    } else if (typeIdent == Ident_Class) {
      Context.setObjCClassType(New);
      return New;
    } else if (typeIdent == Ident_SEL) {
      Context.setObjCSelType(New);
      return New;
    } else if (typeIdent == Ident_Protocol) {
      Context.setObjCProtoType(New->getUnderlyingType());
      return New;
    }
    // Fall through - the typedef name was not a builtin type.
  }
  // Verify the old decl was also a typedef.
  TypedefDecl *Old = dyn_cast<TypedefDecl>(OldD);
  if (!Old) {
    Diag(New->getLocation(), diag::err_redefinition_different_kind,
         New->getName());
    Diag(OldD->getLocation(), diag::err_previous_definition);
    return New;
  }
  
  // If the typedef types are not identical, reject them in all languages and
  // with any extensions enabled.
  if (Old->getUnderlyingType() != New->getUnderlyingType() && 
      Context.getCanonicalType(Old->getUnderlyingType()) != 
      Context.getCanonicalType(New->getUnderlyingType())) {
    Diag(New->getLocation(), diag::err_redefinition_different_typedef,
         New->getUnderlyingType().getAsString(),
         Old->getUnderlyingType().getAsString());
    Diag(Old->getLocation(), diag::err_previous_definition);
    return Old;
  }
  
  if (getLangOptions().Microsoft) return New;

  // Redeclaration of a type is a constraint violation (6.7.2.3p1).
  // Apparently GCC, Intel, and Sun all silently ignore the redeclaration if
  // *either* declaration is in a system header. The code below implements
  // this adhoc compatibility rule. FIXME: The following code will not
  // work properly when compiling ".i" files (containing preprocessed output).
  if (PP.getDiagnostics().getSuppressSystemWarnings()) {
    SourceManager &SrcMgr = Context.getSourceManager();
    if (SrcMgr.isInSystemHeader(Old->getLocation()))
      return New;
    if (SrcMgr.isInSystemHeader(New->getLocation()))
      return New;
  }

  Diag(New->getLocation(), diag::err_redefinition, New->getName());
  Diag(Old->getLocation(), diag::err_previous_definition);
  return New;
}

/// DeclhasAttr - returns true if decl Declaration already has the target
/// attribute.
static bool DeclHasAttr(const Decl *decl, const Attr *target) {
  for (const Attr *attr = decl->getAttrs(); attr; attr = attr->getNext())
    if (attr->getKind() == target->getKind())
      return true;

  return false;
}

/// MergeAttributes - append attributes from the Old decl to the New one.
static void MergeAttributes(Decl *New, Decl *Old) {
  Attr *attr = const_cast<Attr*>(Old->getAttrs()), *tmp;

  while (attr) {
     tmp = attr;
     attr = attr->getNext();

    if (!DeclHasAttr(New, tmp)) {
       New->addAttr(tmp);
    } else {
       tmp->setNext(0);
       delete(tmp);
    }
  }

  Old->invalidateAttrs();
}

/// MergeFunctionDecl - We just parsed a function 'New' from
/// declarator D which has the same name and scope as a previous
/// declaration 'Old'.  Figure out how to resolve this situation,
/// merging decls or emitting diagnostics as appropriate.
/// Redeclaration will be set true if thisNew is a redeclaration OldD.
FunctionDecl *
Sema::MergeFunctionDecl(FunctionDecl *New, Decl *OldD, bool &Redeclaration) {
  Redeclaration = false;
  // Verify the old decl was also a function.
  FunctionDecl *Old = dyn_cast<FunctionDecl>(OldD);
  if (!Old) {
    Diag(New->getLocation(), diag::err_redefinition_different_kind,
         New->getName());
    Diag(OldD->getLocation(), diag::err_previous_definition);
    return New;
  }
  
  QualType OldQType = Context.getCanonicalType(Old->getType());
  QualType NewQType = Context.getCanonicalType(New->getType());
  
  // C++ [dcl.fct]p3:
  //   All declarations for a function shall agree exactly in both the
  //   return type and the parameter-type-list.
  if (getLangOptions().CPlusPlus && OldQType == NewQType) {
    MergeAttributes(New, Old);
    Redeclaration = true;
    return MergeCXXFunctionDecl(New, Old);
  }

  // C: Function types need to be compatible, not identical. This handles
  // duplicate function decls like "void f(int); void f(enum X);" properly.
  if (!getLangOptions().CPlusPlus &&
      Context.typesAreCompatible(OldQType, NewQType)) {
    MergeAttributes(New, Old);
    Redeclaration = true;
    return New;
  }

  // A function that has already been declared has been redeclared or defined
  // with a different type- show appropriate diagnostic
  diag::kind PrevDiag;
  if (Old->isThisDeclarationADefinition())
    PrevDiag = diag::err_previous_definition;
  else if (Old->isImplicit())
    PrevDiag = diag::err_previous_implicit_declaration;
  else 
    PrevDiag = diag::err_previous_declaration;

  // TODO: CHECK FOR CONFLICTS, multiple decls with same name in one scope.
  // TODO: This is totally simplistic.  It should handle merging functions
  // together etc, merging extern int X; int X; ...
  Diag(New->getLocation(), diag::err_conflicting_types, New->getName());
  Diag(Old->getLocation(), PrevDiag);
  return New;
}

/// Predicate for C "tentative" external object definitions (C99 6.9.2).
static bool isTentativeDefinition(VarDecl *VD) {
  if (VD->isFileVarDecl())
    return (!VD->getInit() &&
            (VD->getStorageClass() == VarDecl::None ||
             VD->getStorageClass() == VarDecl::Static));
  return false;
}

/// CheckForFileScopedRedefinitions - Make sure we forgo redefinition errors
/// when dealing with C "tentative" external object definitions (C99 6.9.2).
void Sema::CheckForFileScopedRedefinitions(Scope *S, VarDecl *VD) {
  bool VDIsTentative = isTentativeDefinition(VD);
  bool VDIsIncompleteArray = VD->getType()->isIncompleteArrayType();
  
  for (IdentifierResolver::iterator
       I = IdResolver.begin(VD->getIdentifier(), 
                            VD->getDeclContext(), false/*LookInParentCtx*/), 
       E = IdResolver.end(); I != E; ++I) {
    if (*I != VD && isDeclInScope(*I, VD->getDeclContext(), S)) {
      VarDecl *OldDecl = dyn_cast<VarDecl>(*I);
      
      // Handle the following case:
      //   int a[10];
      //   int a[];   - the code below makes sure we set the correct type. 
      //   int a[11]; - this is an error, size isn't 10.
      if (OldDecl && VDIsTentative && VDIsIncompleteArray && 
          OldDecl->getType()->isConstantArrayType())
        VD->setType(OldDecl->getType());
      
      // Check for "tentative" definitions. We can't accomplish this in 
      // MergeVarDecl since the initializer hasn't been attached.
      if (!OldDecl || isTentativeDefinition(OldDecl) || VDIsTentative)
        continue;
  
      // Handle __private_extern__ just like extern.
      if (OldDecl->getStorageClass() != VarDecl::Extern &&
          OldDecl->getStorageClass() != VarDecl::PrivateExtern &&
          VD->getStorageClass() != VarDecl::Extern &&
          VD->getStorageClass() != VarDecl::PrivateExtern) {
        Diag(VD->getLocation(), diag::err_redefinition, VD->getName());
        Diag(OldDecl->getLocation(), diag::err_previous_definition);
      }
    }
  }
}

/// MergeVarDecl - We just parsed a variable 'New' which has the same name
/// and scope as a previous declaration 'Old'.  Figure out how to resolve this
/// situation, merging decls or emitting diagnostics as appropriate.
///
/// Tentative definition rules (C99 6.9.2p2) are checked by 
/// FinalizeDeclaratorGroup. Unfortunately, we can't analyze tentative 
/// definitions here, since the initializer hasn't been attached.
/// 
VarDecl *Sema::MergeVarDecl(VarDecl *New, Decl *OldD) {
  // Verify the old decl was also a variable.
  VarDecl *Old = dyn_cast<VarDecl>(OldD);
  if (!Old) {
    Diag(New->getLocation(), diag::err_redefinition_different_kind,
         New->getName());
    Diag(OldD->getLocation(), diag::err_previous_definition);
    return New;
  }

  MergeAttributes(New, Old);

  // Verify the types match.
  QualType OldCType = Context.getCanonicalType(Old->getType());
  QualType NewCType = Context.getCanonicalType(New->getType());
  if (OldCType != NewCType && !Context.typesAreCompatible(OldCType, NewCType)) {
    Diag(New->getLocation(), diag::err_redefinition, New->getName());
    Diag(Old->getLocation(), diag::err_previous_definition);
    return New;
  }
  // C99 6.2.2p4: Check if we have a static decl followed by a non-static.
  if (New->getStorageClass() == VarDecl::Static &&
      (Old->getStorageClass() == VarDecl::None ||
       Old->getStorageClass() == VarDecl::Extern)) {
    Diag(New->getLocation(), diag::err_static_non_static, New->getName());
    Diag(Old->getLocation(), diag::err_previous_definition);
    return New;
  }
  // C99 6.2.2p4: Check if we have a non-static decl followed by a static.
  if (New->getStorageClass() != VarDecl::Static &&
      Old->getStorageClass() == VarDecl::Static) {
    Diag(New->getLocation(), diag::err_non_static_static, New->getName());
    Diag(Old->getLocation(), diag::err_previous_definition);
    return New;
  }
  // Variables with external linkage are analyzed in FinalizeDeclaratorGroup.
  if (New->getStorageClass() != VarDecl::Extern && !New->isFileVarDecl()) {
    Diag(New->getLocation(), diag::err_redefinition, New->getName());
    Diag(Old->getLocation(), diag::err_previous_definition);
  }
  return New;
}

/// CheckParmsForFunctionDef - Check that the parameters of the given
/// function are appropriate for the definition of a function. This
/// takes care of any checks that cannot be performed on the
/// declaration itself, e.g., that the types of each of the function
/// parameters are complete.
bool Sema::CheckParmsForFunctionDef(FunctionDecl *FD) {
  bool HasInvalidParm = false;
  for (unsigned p = 0, NumParams = FD->getNumParams(); p < NumParams; ++p) {
    ParmVarDecl *Param = FD->getParamDecl(p);

    // C99 6.7.5.3p4: the parameters in a parameter type list in a
    // function declarator that is part of a function definition of
    // that function shall not have incomplete type.
    if (Param->getType()->isIncompleteType() &&
        !Param->isInvalidDecl()) {
      Diag(Param->getLocation(), diag::err_typecheck_decl_incomplete_type,
           Param->getType().getAsString());
      Param->setInvalidDecl();
      HasInvalidParm = true;
    }
  }

  return HasInvalidParm;
}

/// ParsedFreeStandingDeclSpec - This method is invoked when a declspec with
/// no declarator (e.g. "struct foo;") is parsed.
Sema::DeclTy *Sema::ParsedFreeStandingDeclSpec(Scope *S, DeclSpec &DS) {
  // TODO: emit error on 'int;' or 'const enum foo;'.
  // TODO: emit error on 'typedef int;'
  // if (!DS.isMissingDeclaratorOk()) Diag(...);
  
  return dyn_cast_or_null<TagDecl>(static_cast<Decl *>(DS.getTypeRep()));
}

bool Sema::CheckSingleInitializer(Expr *&Init, QualType DeclType) {  
  // Get the type before calling CheckSingleAssignmentConstraints(), since
  // it can promote the expression.
  QualType InitType = Init->getType(); 
  
  AssignConvertType ConvTy = CheckSingleAssignmentConstraints(DeclType, Init);
  return DiagnoseAssignmentResult(ConvTy, Init->getLocStart(), DeclType,
                                  InitType, Init, "initializing");
}

bool Sema::CheckStringLiteralInit(StringLiteral *strLiteral, QualType &DeclT) {
  const ArrayType *AT = Context.getAsArrayType(DeclT);
  
  if (const IncompleteArrayType *IAT = dyn_cast<IncompleteArrayType>(AT)) {
    // C99 6.7.8p14. We have an array of character type with unknown size 
    // being initialized to a string literal.
    llvm::APSInt ConstVal(32);
    ConstVal = strLiteral->getByteLength() + 1;
    // Return a new array type (C99 6.7.8p22).
    DeclT = Context.getConstantArrayType(IAT->getElementType(), ConstVal, 
                                         ArrayType::Normal, 0);
  } else {
    const ConstantArrayType *CAT = cast<ConstantArrayType>(AT);
    // C99 6.7.8p14. We have an array of character type with known size.
    // FIXME: Avoid truncation for 64-bit length strings.
    if (strLiteral->getByteLength() > (unsigned)CAT->getSize().getZExtValue())
      Diag(strLiteral->getSourceRange().getBegin(),
           diag::warn_initializer_string_for_char_array_too_long,
           strLiteral->getSourceRange());
  }
  // Set type from "char *" to "constant array of char".
  strLiteral->setType(DeclT);
  // For now, we always return false (meaning success).
  return false;
}

StringLiteral *Sema::IsStringLiteralInit(Expr *Init, QualType DeclType) {
  const ArrayType *AT = Context.getAsArrayType(DeclType);
  if (AT && AT->getElementType()->isCharType()) {
    return dyn_cast<StringLiteral>(Init);
  }
  return 0;
}

bool Sema::CheckInitializerTypes(Expr *&Init, QualType &DeclType) {  
  // C99 6.7.8p3: The type of the entity to be initialized shall be an array
  // of unknown size ("[]") or an object type that is not a variable array type.
  if (const VariableArrayType *VAT = Context.getAsVariableArrayType(DeclType))
    return Diag(VAT->getSizeExpr()->getLocStart(), 
                diag::err_variable_object_no_init, 
                VAT->getSizeExpr()->getSourceRange());
  
  InitListExpr *InitList = dyn_cast<InitListExpr>(Init);
  if (!InitList) {
    // FIXME: Handle wide strings
    if (StringLiteral *strLiteral = IsStringLiteralInit(Init, DeclType))
      return CheckStringLiteralInit(strLiteral, DeclType);

    // C99 6.7.8p16.
    if (DeclType->isArrayType())
      return Diag(Init->getLocStart(),
                  diag::err_array_init_list_required, 
                  Init->getSourceRange());

    return CheckSingleInitializer(Init, DeclType);
  }

  InitListChecker CheckInitList(this, InitList, DeclType);
  return CheckInitList.HadError();
}

Sema::DeclTy *
Sema::ActOnDeclarator(Scope *S, Declarator &D, DeclTy *lastDecl) {
  ScopedDecl *LastDeclarator = dyn_cast_or_null<ScopedDecl>((Decl *)lastDecl);
  IdentifierInfo *II = D.getIdentifier();
  
  // All of these full declarators require an identifier.  If it doesn't have
  // one, the ParsedFreeStandingDeclSpec action should be used.
  if (II == 0) {
    Diag(D.getDeclSpec().getSourceRange().getBegin(),
         diag::err_declarator_need_ident,
         D.getDeclSpec().getSourceRange(), D.getSourceRange());
    return 0;
  }
  
  // The scope passed in may not be a decl scope.  Zip up the scope tree until
  // we find one that is.
  while ((S->getFlags() & Scope::DeclScope) == 0)
    S = S->getParent();
  
  // See if this is a redefinition of a variable in the same scope.
  Decl *PrevDecl = LookupDecl(II, Decl::IDNS_Ordinary, S);
  ScopedDecl *New;
  bool InvalidDecl = false;
 
  // In C++, the previous declaration we find might be a tag type
  // (class or enum). In this case, the new declaration will hide the
  // tag type. 
  if (PrevDecl && PrevDecl->getIdentifierNamespace() == Decl::IDNS_Tag)
    PrevDecl = 0;

  QualType R = GetTypeForDeclarator(D, S);
  assert(!R.isNull() && "GetTypeForDeclarator() returned null type");

  if (D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_typedef) {
    // Check that there are no default arguments (C++ only).
    if (getLangOptions().CPlusPlus)
      CheckExtraCXXDefaultArguments(D);

    TypedefDecl *NewTD = ParseTypedefDecl(S, D, R, LastDeclarator);
    if (!NewTD) return 0;

    // Handle attributes prior to checking for duplicates in MergeVarDecl
    ProcessDeclAttributes(NewTD, D);
    // Merge the decl with the existing one if appropriate. If the decl is
    // in an outer scope, it isn't the same thing.
    if (PrevDecl && isDeclInScope(PrevDecl, CurContext, S)) {
      NewTD = MergeTypeDefDecl(NewTD, PrevDecl);
      if (NewTD == 0) return 0;
    }
    New = NewTD;
    if (S->getFnParent() == 0) {
      // C99 6.7.7p2: If a typedef name specifies a variably modified type
      // then it shall have block scope.
      if (NewTD->getUnderlyingType()->isVariablyModifiedType()) {
        // FIXME: Diagnostic needs to be fixed.
        Diag(D.getIdentifierLoc(), diag::err_typecheck_illegal_vla);
        InvalidDecl = true;
      }
    }
  } else if (R.getTypePtr()->isFunctionType()) {
    FunctionDecl::StorageClass SC = FunctionDecl::None;
    switch (D.getDeclSpec().getStorageClassSpec()) {
      default: assert(0 && "Unknown storage class!");
      case DeclSpec::SCS_auto:        
      case DeclSpec::SCS_register:
        Diag(D.getIdentifierLoc(), diag::err_typecheck_sclass_func,
             R.getAsString());
        InvalidDecl = true;
        break;
      case DeclSpec::SCS_unspecified: SC = FunctionDecl::None; break;
      case DeclSpec::SCS_extern:      SC = FunctionDecl::Extern; break;
      case DeclSpec::SCS_static:      SC = FunctionDecl::Static; break;
      case DeclSpec::SCS_private_extern: SC = FunctionDecl::PrivateExtern;break;
    }

    bool isInline = D.getDeclSpec().isInlineSpecified();
    FunctionDecl *NewFD;
    if (D.getContext() == Declarator::MemberContext) {
      // This is a C++ method declaration.
      NewFD = CXXMethodDecl::Create(Context, cast<CXXRecordDecl>(CurContext),
                                    D.getIdentifierLoc(), II, R,
                                    (SC == FunctionDecl::Static), isInline,
                                    LastDeclarator);
    } else {
      NewFD = FunctionDecl::Create(Context, CurContext,
                                   D.getIdentifierLoc(),
                                   II, R, SC, isInline,
                                   LastDeclarator);
    }
    // Handle attributes.
    ProcessDeclAttributes(NewFD, D);

    // Handle GNU asm-label extension (encoded as an attribute).
    if (Expr *E = (Expr*) D.getAsmLabel()) {
      // The parser guarantees this is a string.
      StringLiteral *SE = cast<StringLiteral>(E);  
      NewFD->addAttr(new AsmLabelAttr(std::string(SE->getStrData(),
                                                  SE->getByteLength())));
    }

    // Copy the parameter declarations from the declarator D to
    // the function declaration NewFD, if they are available.
    if (D.getNumTypeObjects() > 0) {
      DeclaratorChunk::FunctionTypeInfo &FTI = D.getTypeObject(0).Fun;

      // Create Decl objects for each parameter, adding them to the
      // FunctionDecl.
      llvm::SmallVector<ParmVarDecl*, 16> Params;
  
      // Check for C99 6.7.5.3p10 - foo(void) is a non-varargs
      // function that takes no arguments, not a function that takes a
      // single void argument.
      // We let through "const void" here because Sema::GetTypeForDeclarator
      // already checks for that case.
      if (FTI.NumArgs == 1 && !FTI.isVariadic && FTI.ArgInfo[0].Ident == 0 &&
          FTI.ArgInfo[0].Param &&
          ((ParmVarDecl*)FTI.ArgInfo[0].Param)->getType()->isVoidType()) {
        // empty arg list, don't push any params.
        ParmVarDecl *Param = (ParmVarDecl*)FTI.ArgInfo[0].Param;

        // In C++, the empty parameter-type-list must be spelled "void"; a
        // typedef of void is not permitted.
        if (getLangOptions().CPlusPlus &&
            Param->getType().getUnqualifiedType() != Context.VoidTy) {
          Diag(Param->getLocation(), diag::ext_param_typedef_of_void);
        }

      } else if (FTI.NumArgs > 0 && FTI.ArgInfo[0].Param != 0) {
        for (unsigned i = 0, e = FTI.NumArgs; i != e; ++i)
          Params.push_back((ParmVarDecl *)FTI.ArgInfo[i].Param);
      }
  
      NewFD->setParams(&Params[0], Params.size());
    }

    // Merge the decl with the existing one if appropriate. Since C functions
    // are in a flat namespace, make sure we consider decls in outer scopes.
    if (PrevDecl &&
        (!getLangOptions().CPlusPlus||isDeclInScope(PrevDecl, CurContext, S))) {
      bool Redeclaration = false;
      NewFD = MergeFunctionDecl(NewFD, PrevDecl, Redeclaration);
      if (NewFD == 0) return 0;
      if (Redeclaration) {
        NewFD->setPreviousDeclaration(cast<FunctionDecl>(PrevDecl));
      }
    }
    New = NewFD;

    // In C++, check default arguments now that we have merged decls.
    if (getLangOptions().CPlusPlus)
      CheckCXXDefaultArguments(NewFD);
  } else {
    // Check that there are no default arguments (C++ only).
    if (getLangOptions().CPlusPlus)
      CheckExtraCXXDefaultArguments(D);

    if (R.getTypePtr()->isObjCInterfaceType()) {
      Diag(D.getIdentifierLoc(), diag::err_statically_allocated_object,
           D.getIdentifier()->getName());
      InvalidDecl = true;
    }

    VarDecl *NewVD;
    VarDecl::StorageClass SC;
    switch (D.getDeclSpec().getStorageClassSpec()) {
    default: assert(0 && "Unknown storage class!");
    case DeclSpec::SCS_unspecified:    SC = VarDecl::None; break;
    case DeclSpec::SCS_extern:         SC = VarDecl::Extern; break;
    case DeclSpec::SCS_static:         SC = VarDecl::Static; break;
    case DeclSpec::SCS_auto:           SC = VarDecl::Auto; break;
    case DeclSpec::SCS_register:       SC = VarDecl::Register; break;
    case DeclSpec::SCS_private_extern: SC = VarDecl::PrivateExtern; break;
    }    
    if (D.getContext() == Declarator::MemberContext) {
      assert(SC == VarDecl::Static && "Invalid storage class for member!");
      // This is a static data member for a C++ class.
      NewVD = CXXClassVarDecl::Create(Context, cast<CXXRecordDecl>(CurContext),
                                      D.getIdentifierLoc(), II,
                                      R, LastDeclarator);
    } else {
      bool ThreadSpecified = D.getDeclSpec().isThreadSpecified();
      if (S->getFnParent() == 0) {
        // C99 6.9p2: The storage-class specifiers auto and register shall not
        // appear in the declaration specifiers in an external declaration.
        if (SC == VarDecl::Auto || SC == VarDecl::Register) {
          Diag(D.getIdentifierLoc(), diag::err_typecheck_sclass_fscope,
               R.getAsString());
          InvalidDecl = true;
        }
      }
        NewVD = VarDecl::Create(Context, CurContext, D.getIdentifierLoc(), 
                                II, R, SC, LastDeclarator);
        NewVD->setThreadSpecified(ThreadSpecified);
    }
    // Handle attributes prior to checking for duplicates in MergeVarDecl
    ProcessDeclAttributes(NewVD, D);

    // Handle GNU asm-label extension (encoded as an attribute).
    if (Expr *E = (Expr*) D.getAsmLabel()) {
      // The parser guarantees this is a string.
      StringLiteral *SE = cast<StringLiteral>(E);  
      NewVD->addAttr(new AsmLabelAttr(std::string(SE->getStrData(),
                                                  SE->getByteLength())));
    }

    // Emit an error if an address space was applied to decl with local storage.
    // This includes arrays of objects with address space qualifiers, but not
    // automatic variables that point to other address spaces.
    // ISO/IEC TR 18037 S5.1.2
    if (NewVD->hasLocalStorage() && (NewVD->getType().getAddressSpace() != 0)) {
      Diag(D.getIdentifierLoc(), diag::err_as_qualified_auto_decl);
      InvalidDecl = true;
    }
    // Merge the decl with the existing one if appropriate. If the decl is
    // in an outer scope, it isn't the same thing.
    if (PrevDecl && isDeclInScope(PrevDecl, CurContext, S)) {
      NewVD = MergeVarDecl(NewVD, PrevDecl);
      if (NewVD == 0) return 0;
    }
    New = NewVD;
  }
  
  // If this has an identifier, add it to the scope stack.
  if (II)
    PushOnScopeChains(New, S);
  // If any semantic error occurred, mark the decl as invalid.
  if (D.getInvalidType() || InvalidDecl)
    New->setInvalidDecl();
  
  return New;
}

bool Sema::CheckAddressConstantExpressionLValue(const Expr* Init) {
  switch (Init->getStmtClass()) {
  default:
    Diag(Init->getExprLoc(),
         diag::err_init_element_not_constant, Init->getSourceRange());
    return true;
  case Expr::ParenExprClass: {
    const ParenExpr* PE = cast<ParenExpr>(Init);
    return CheckAddressConstantExpressionLValue(PE->getSubExpr());
  }
  case Expr::CompoundLiteralExprClass:
    return cast<CompoundLiteralExpr>(Init)->isFileScope();
  case Expr::DeclRefExprClass: {
    const Decl *D = cast<DeclRefExpr>(Init)->getDecl();
    if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
      if (VD->hasGlobalStorage())
        return false;
      Diag(Init->getExprLoc(),
           diag::err_init_element_not_constant, Init->getSourceRange());
      return true;
    }
    if (isa<FunctionDecl>(D))
      return false;
    Diag(Init->getExprLoc(),
         diag::err_init_element_not_constant, Init->getSourceRange());
    return true;
  }
  case Expr::MemberExprClass: {
    const MemberExpr *M = cast<MemberExpr>(Init);
    if (M->isArrow())
      return CheckAddressConstantExpression(M->getBase());
    return CheckAddressConstantExpressionLValue(M->getBase());
  }
  case Expr::ArraySubscriptExprClass: {
    // FIXME: Should we pedwarn for "x[0+0]" (where x is a pointer)?
    const ArraySubscriptExpr *ASE = cast<ArraySubscriptExpr>(Init);
    return CheckAddressConstantExpression(ASE->getBase()) ||
           CheckArithmeticConstantExpression(ASE->getIdx());
  }
  case Expr::StringLiteralClass:
  case Expr::PredefinedExprClass:
    return false;
  case Expr::UnaryOperatorClass: {
    const UnaryOperator *Exp = cast<UnaryOperator>(Init);

    // C99 6.6p9
    if (Exp->getOpcode() == UnaryOperator::Deref)
      return CheckAddressConstantExpression(Exp->getSubExpr());

    Diag(Init->getExprLoc(),
         diag::err_init_element_not_constant, Init->getSourceRange());
    return true;
  }
  }
}

bool Sema::CheckAddressConstantExpression(const Expr* Init) {
  switch (Init->getStmtClass()) {
  default:
    Diag(Init->getExprLoc(),
         diag::err_init_element_not_constant, Init->getSourceRange());
    return true;
  case Expr::ParenExprClass: {
    const ParenExpr* PE = cast<ParenExpr>(Init);
    return CheckAddressConstantExpression(PE->getSubExpr());
  }
  case Expr::StringLiteralClass:
  case Expr::ObjCStringLiteralClass:
    return false;
  case Expr::CallExprClass: {
    const CallExpr *CE = cast<CallExpr>(Init);
    if (CE->isBuiltinConstantExpr())
      return false;
    Diag(Init->getExprLoc(),
         diag::err_init_element_not_constant, Init->getSourceRange());
    return true;
  }
  case Expr::UnaryOperatorClass: {
    const UnaryOperator *Exp = cast<UnaryOperator>(Init);

    // C99 6.6p9
    if (Exp->getOpcode() == UnaryOperator::AddrOf)
      return CheckAddressConstantExpressionLValue(Exp->getSubExpr());

    if (Exp->getOpcode() == UnaryOperator::Extension)
      return CheckAddressConstantExpression(Exp->getSubExpr());
  
    Diag(Init->getExprLoc(),
         diag::err_init_element_not_constant, Init->getSourceRange());
    return true;
  }
  case Expr::BinaryOperatorClass: {
    // FIXME: Should we pedwarn for expressions like "a + 1 + 2"?
    const BinaryOperator *Exp = cast<BinaryOperator>(Init);

    Expr *PExp = Exp->getLHS();
    Expr *IExp = Exp->getRHS();
    if (IExp->getType()->isPointerType())
      std::swap(PExp, IExp);

    // FIXME: Should we pedwarn if IExp isn't an integer constant expression?
    return CheckAddressConstantExpression(PExp) ||
           CheckArithmeticConstantExpression(IExp);
  }
  case Expr::ImplicitCastExprClass:
  case Expr::ExplicitCastExprClass: {
    const Expr* SubExpr = cast<CastExpr>(Init)->getSubExpr();
    if (Init->getStmtClass() == Expr::ImplicitCastExprClass) {
      // Check for implicit promotion
      if (SubExpr->getType()->isFunctionType() ||
          SubExpr->getType()->isArrayType())
        return CheckAddressConstantExpressionLValue(SubExpr);
    }

    // Check for pointer->pointer cast
    if (SubExpr->getType()->isPointerType())
      return CheckAddressConstantExpression(SubExpr);

    if (SubExpr->getType()->isIntegralType()) {
      // Check for the special-case of a pointer->int->pointer cast;
      // this isn't standard, but some code requires it. See
      // PR2720 for an example.
      if (const CastExpr* SubCast = dyn_cast<CastExpr>(SubExpr)) {
        if (SubCast->getSubExpr()->getType()->isPointerType()) {
          unsigned IntWidth = Context.getIntWidth(SubCast->getType());
          unsigned PointerWidth = Context.getTypeSize(Context.VoidPtrTy);
          if (IntWidth >= PointerWidth) {
            return CheckAddressConstantExpression(SubCast->getSubExpr());
          }
        }
      }
    }
    if (SubExpr->getType()->isArithmeticType()) {
      return CheckArithmeticConstantExpression(SubExpr);
    }

    Diag(Init->getExprLoc(),
         diag::err_init_element_not_constant, Init->getSourceRange());
    return true;
  }
  case Expr::ConditionalOperatorClass: {
    // FIXME: Should we pedwarn here?
    const ConditionalOperator *Exp = cast<ConditionalOperator>(Init);
    if (!Exp->getCond()->getType()->isArithmeticType()) {
      Diag(Init->getExprLoc(),
           diag::err_init_element_not_constant, Init->getSourceRange());
      return true;
    }
    if (CheckArithmeticConstantExpression(Exp->getCond()))
      return true;
    if (Exp->getLHS() &&
        CheckAddressConstantExpression(Exp->getLHS()))
      return true;
    return CheckAddressConstantExpression(Exp->getRHS());
  }
  case Expr::AddrLabelExprClass:
    return false;
  }
}

static const Expr* FindExpressionBaseAddress(const Expr* E);

static const Expr* FindExpressionBaseAddressLValue(const Expr* E) {
  switch (E->getStmtClass()) {
  default:
    return E;
  case Expr::ParenExprClass: {
    const ParenExpr* PE = cast<ParenExpr>(E);
    return FindExpressionBaseAddressLValue(PE->getSubExpr());
  }
  case Expr::MemberExprClass: {
    const MemberExpr *M = cast<MemberExpr>(E);
    if (M->isArrow())
      return FindExpressionBaseAddress(M->getBase());
    return FindExpressionBaseAddressLValue(M->getBase());
  }
  case Expr::ArraySubscriptExprClass: {
    const ArraySubscriptExpr *ASE = cast<ArraySubscriptExpr>(E);
    return FindExpressionBaseAddress(ASE->getBase());
  }
  case Expr::UnaryOperatorClass: {
    const UnaryOperator *Exp = cast<UnaryOperator>(E);

    if (Exp->getOpcode() == UnaryOperator::Deref)
      return FindExpressionBaseAddress(Exp->getSubExpr());

    return E;
  }
  }
}