source: src/SymTab/Indexer.cc @ 0e7ea335

//
// Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// Indexer.cc --
//
// Author           : Richard C. Bilson
// Created On       : Sun May 17 21:37:33 2015
// Last Modified By : Peter A. Buhr
// Last Modified On : Tue Mar  7 07:45:32 2017
// Update Count     : 16
//

#include "Indexer.h"

#include <string>
#include <typeinfo>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <algorithm>

#include "Mangler.h"

#include "Common/utility.h"

#include "ResolvExpr/typeops.h"

#include "SynTree/Declaration.h"
#include "SynTree/Type.h"
#include "SynTree/Expression.h"
#include "SynTree/Initializer.h"
#include "SynTree/Statement.h"

#include "InitTweak/InitTweak.h"

#define debugPrint(x) if ( doDebug ) { std::cout << x; }

namespace SymTab {
        struct NewScope {
                NewScope( SymTab::Indexer & indexer ) : indexer( indexer ) { indexer.enterScope(); }
                ~NewScope() { indexer.leaveScope(); }
                SymTab::Indexer & indexer;
        };

        template< typename TreeType, typename VisitorType >
        inline void acceptNewScope( TreeType *tree, VisitorType &visitor ) {
                visitor.enterScope();
                maybeAccept( tree, visitor );
                visitor.leaveScope();
        }

        typedef std::unordered_map< std::string, DeclarationWithType* > MangleTable;
        typedef std::unordered_map< std::string, MangleTable > IdTable;
        typedef std::unordered_map< std::string, NamedTypeDecl* > TypeTable;
        typedef std::unordered_map< std::string, StructDecl* > StructTable;
        typedef std::unordered_map< std::string, EnumDecl* > EnumTable;
        typedef std::unordered_map< std::string, UnionDecl* > UnionTable;
        typedef std::unordered_map< std::string, TraitDecl* > TraitTable;

        void dump( const IdTable &table, std::ostream &os ) {
                for ( IdTable::const_iterator id = table.begin(); id != table.end(); ++id ) {
                        for ( MangleTable::const_iterator mangle = id->second.begin(); mangle != id->second.end(); ++mangle ) {
                                os << mangle->second << std::endl;
                        }
                }
        }

        template< typename Decl >
        void dump( const std::unordered_map< std::string, Decl* > &table, std::ostream &os ) {
                for ( typename std::unordered_map< std::string, Decl* >::const_iterator it = table.begin(); it != table.end(); ++it ) {
                        os << it->second << std::endl;
                } // for
        }

        struct Indexer::Impl {
                Impl( unsigned long _scope ) : refCount(1), scope( _scope ), size( 0 ), base(),
                                idTable(), typeTable(), structTable(), enumTable(), unionTable(), traitTable() {}
                Impl( unsigned long _scope, Indexer &&_base ) : refCount(1), scope( _scope ), size( 0 ), base( _base ),
                                idTable(), typeTable(), structTable(), enumTable(), unionTable(), traitTable() {}
                unsigned long refCount;   ///< Number of references to these tables
                unsigned long scope;      ///< Scope these tables are associated with
                unsigned long size;       ///< Number of elements stored in this table
                const Indexer base;       ///< Base indexer this extends

                IdTable idTable;          ///< Identifier namespace
                TypeTable typeTable;      ///< Type namespace
                StructTable structTable;  ///< Struct namespace
                EnumTable enumTable;      ///< Enum namespace
                UnionTable unionTable;    ///< Union namespace
                TraitTable traitTable;    ///< Trait namespace
        };

        Indexer::Impl *Indexer::newRef( Indexer::Impl *toClone ) {
                if ( ! toClone ) return 0;

                // shorten the search chain by skipping empty links
                Indexer::Impl *ret = toClone->size == 0 ? toClone->base.tables : toClone;
                if ( ret ) { ++ret->refCount; }

                return ret;
        }

        void Indexer::deleteRef( Indexer::Impl *toFree ) {
                if ( ! toFree ) return;

                if ( --toFree->refCount == 0 ) delete toFree;
        }

        void Indexer::removeSpecialOverrides( const std::string &id, std::list< DeclarationWithType * > & out ) const {
                // only need to perform this step for constructors, destructors, and assignment functions
                if ( ! InitTweak::isCtorDtorAssign( id ) ) return;

                // helpful data structure
                struct ValueType {
                        struct DeclBall {
                                FunctionDecl * decl;
                                bool isUserDefinedFunc; // properties for this particular decl
                                bool isDefaultFunc;
                                bool isCopyFunc;
                        };
                        // properties for this type
                        bool userDefinedFunc = false; // any user defined function found
                        bool userDefinedDefaultFunc = false; // user defined default ctor found
                        bool userDefinedCopyFunc = false; // user defined copy ctor found
                        std::list< DeclBall > decls;

                        // another FunctionDecl for the current type was found - determine
                        // if it has special properties and update data structure accordingly
                        ValueType & operator+=( FunctionDecl * function ) {
                                bool isUserDefinedFunc = ! LinkageSpec::isOverridable( function->get_linkage() );
                                bool isDefaultFunc = function->get_functionType()->get_parameters().size() == 1;
                                bool isCopyFunc = InitTweak::isCopyFunction( function, function->get_name() );
                                decls.push_back( DeclBall{ function, isUserDefinedFunc, isDefaultFunc, isCopyFunc } );
                                userDefinedFunc = userDefinedFunc || isUserDefinedFunc;
                                userDefinedDefaultFunc = userDefinedDefaultFunc || (isUserDefinedFunc && isDefaultFunc);
                                userDefinedCopyFunc = userDefinedCopyFunc || (isUserDefinedFunc && isCopyFunc);
                                return *this;
                        }
                }; // ValueType

                std::list< DeclarationWithType * > copy;
                copy.splice( copy.end(), out );

                // organize discovered declarations by type
                std::unordered_map< std::string, ValueType > funcMap;
                for ( DeclarationWithType * decl : copy ) {
                        if ( FunctionDecl * function = dynamic_cast< FunctionDecl * >( decl ) ) {
                                std::list< DeclarationWithType * > & params = function->get_functionType()->get_parameters();
                                assert( ! params.empty() );
                                // use base type of pointer, so that qualifiers on the pointer type aren't considered.
                                Type * base = safe_dynamic_cast< PointerType * >( params.front()->get_type() )->get_base();
                                funcMap[ Mangler::mangle( base ) ] += function;
                        } else {
                                out.push_back( decl );
                        }
                }

                // if a type contains user defined ctor/dtors, then special rules trigger, which determine
                // the set of ctor/dtors that are seen by the requester. In particular, if the user defines
                // a default ctor, then the generated default ctor should never be seen, likewise for copy ctor
                // and dtor. If the user defines any ctor/dtor, then no generated field ctors should be seen.
                for ( std::pair< const std::string, ValueType > & pair : funcMap ) {
                        ValueType & val = pair.second;
                        for ( ValueType::DeclBall ball : val.decls ) {
                                if ( ! val.userDefinedFunc || ball.isUserDefinedFunc || (! val.userDefinedDefaultFunc && ball.isDefaultFunc) || (! val.userDefinedCopyFunc && ball.isCopyFunc) ) {
                                        // decl conforms to the rules described above, so it should be seen by the requester
                                        out.push_back( ball.decl );
                                }
                        }
                }
        }

        void Indexer::makeWritable() {
                if ( ! tables ) {
                        // create indexer if not yet set
                        tables = new Indexer::Impl( scope );
                } else if ( tables->refCount > 1 || tables->scope != scope ) {
                        // make this indexer the base of a fresh indexer at the current scope
                        tables = new Indexer::Impl( scope, std::move( *this ) );
                }
        }

        Indexer::Indexer( bool _doDebug ) : tables( 0 ), scope( 0 ), doDebug( _doDebug ) {}

        Indexer::Indexer( const Indexer &that ) : tables( newRef( that.tables ) ), scope( that.scope ), doDebug( that.doDebug ) {}

        Indexer::Indexer( Indexer &&that ) : tables( that.tables ), scope( that.scope ), doDebug( that.doDebug ) {
                that.tables = 0;
        }

        Indexer::~Indexer() {
                deleteRef( tables );
        }

        Indexer& Indexer::operator= ( const Indexer &that ) {
                deleteRef( tables );

                tables = newRef( that.tables );
                scope = that.scope;
                doDebug = that.doDebug;

                return *this;
        }

        Indexer& Indexer::operator= ( Indexer &&that ) {
                deleteRef( tables );

                tables = that.tables;
                scope = that.scope;
                doDebug = that.doDebug;

                that.tables = 0;

                return *this;
        }

        void Indexer::visit( ObjectDecl *objectDecl ) {
                enterScope();
                maybeAccept( objectDecl->get_type(), *this );
                leaveScope();
                maybeAccept( objectDecl->get_init(), *this );
                maybeAccept( objectDecl->get_bitfieldWidth(), *this );
                if ( objectDecl->get_name() != "" ) {
                        debugPrint( "Adding object " << objectDecl->get_name() << std::endl );
                        addId( objectDecl );
                } // if
        }

        void Indexer::visit( FunctionDecl *functionDecl ) {
                if ( functionDecl->get_name() == "" ) return;
                debugPrint( "Adding function " << functionDecl->get_name() << std::endl );
                addId( functionDecl );
                enterScope();
                maybeAccept( functionDecl->get_functionType(), *this );
                maybeAccept( functionDecl->get_statements(), *this );
                leaveScope();
        }


// A NOTE ON THE ORDER OF TRAVERSAL
//
// Types and typedefs have their base types visited before they are added to the type table.  This is ok, since there is
// no such thing as a recursive type or typedef.
//
//             typedef struct { T *x; } T; // never allowed
//
// for structs/unions, it is possible to have recursion, so the decl should be added as if it's incomplete to begin, the
// members are traversed, and then the complete type should be added (assuming the type is completed by this particular
// declaration).
//
//             struct T { struct T *x; }; // allowed
//
// It is important to add the complete type to the symbol table *after* the members/base has been traversed, since that
// traversal may modify the definition of the type and these modifications should be visible when the symbol table is
// queried later in this pass.
//
// TODO: figure out whether recursive contexts are sensible/possible/reasonable.


        void Indexer::visit( TypeDecl *typeDecl ) {
                // see A NOTE ON THE ORDER OF TRAVERSAL, above
                // note that assertions come after the type is added to the symtab, since they are not part of the type proper
                // and may depend on the type itself
                enterScope();
                acceptAll( typeDecl->get_parameters(), *this );
                maybeAccept( typeDecl->get_base(), *this );
                leaveScope();
                debugPrint( "Adding type " << typeDecl->get_name() << std::endl );
                addType( typeDecl );
                acceptAll( typeDecl->get_assertions(), *this );
        }

        void Indexer::visit( TypedefDecl *typeDecl ) {
                enterScope();
                acceptAll( typeDecl->get_parameters(), *this );
                maybeAccept( typeDecl->get_base(), *this );
                leaveScope();
                debugPrint( "Adding typedef " << typeDecl->get_name() << std::endl );
                addType( typeDecl );
        }

        void Indexer::visit( StructDecl *aggregateDecl ) {
                // make up a forward declaration and add it before processing the members
                // needs to be on the heap because addStruct saves the pointer
                StructDecl &fwdDecl = *new StructDecl( aggregateDecl->get_name() );
                cloneAll( aggregateDecl->get_parameters(), fwdDecl.get_parameters() );
                debugPrint( "Adding fwd decl for struct " << fwdDecl.get_name() << std::endl );
                addStruct( &fwdDecl );

                enterScope();
                acceptAll( aggregateDecl->get_parameters(), *this );
                acceptAll( aggregateDecl->get_members(), *this );
                leaveScope();

                debugPrint( "Adding struct " << aggregateDecl->get_name() << std::endl );
                // this addition replaces the forward declaration
                addStruct( aggregateDecl );
        }

        void Indexer::visit( UnionDecl *aggregateDecl ) {
                // make up a forward declaration and add it before processing the members
                UnionDecl fwdDecl( aggregateDecl->get_name() );
                cloneAll( aggregateDecl->get_parameters(), fwdDecl.get_parameters() );
                debugPrint( "Adding fwd decl for union " << fwdDecl.get_name() << std::endl );
                addUnion( &fwdDecl );

                enterScope();
                acceptAll( aggregateDecl->get_parameters(), *this );
                acceptAll( aggregateDecl->get_members(), *this );
                leaveScope();

                debugPrint( "Adding union " << aggregateDecl->get_name() << std::endl );
                addUnion( aggregateDecl );
        }

        void Indexer::visit( EnumDecl *aggregateDecl ) {
                debugPrint( "Adding enum " << aggregateDecl->get_name() << std::endl );
                addEnum( aggregateDecl );
                // unlike structs, contexts, and unions, enums inject their members into the global scope
                acceptAll( aggregateDecl->get_members(), *this );
        }

        void Indexer::visit( TraitDecl *aggregateDecl ) {
                enterScope();
                acceptAll( aggregateDecl->get_parameters(), *this );
                acceptAll( aggregateDecl->get_members(), *this );
                leaveScope();

                debugPrint( "Adding context " << aggregateDecl->get_name() << std::endl );
                addTrait( aggregateDecl );
        }

        void Indexer::visit( CompoundStmt *compoundStmt ) {
                enterScope();
                acceptAll( compoundStmt->get_kids(), *this );
                leaveScope();
        }


        void Indexer::visit( ApplicationExpr *applicationExpr ) {
                acceptNewScope( applicationExpr->get_result(), *this );
                maybeAccept( applicationExpr->get_function(), *this );
                acceptAll( applicationExpr->get_args(), *this );
        }

        void Indexer::visit( UntypedExpr *untypedExpr ) {
                acceptNewScope( untypedExpr->get_result(), *this );
                acceptAll( untypedExpr->get_args(), *this );
        }

        void Indexer::visit( NameExpr *nameExpr ) {
                acceptNewScope( nameExpr->get_result(), *this );
        }

        void Indexer::visit( AddressExpr *addressExpr ) {
                acceptNewScope( addressExpr->get_result(), *this );
                maybeAccept( addressExpr->get_arg(), *this );
        }

        void Indexer::visit( LabelAddressExpr *labAddressExpr ) {
                acceptNewScope( labAddressExpr->get_result(), *this );
                maybeAccept( labAddressExpr->get_arg(), *this );
        }

        void Indexer::visit( CastExpr *castExpr ) {
                acceptNewScope( castExpr->get_result(), *this );
                maybeAccept( castExpr->get_arg(), *this );
        }

        void Indexer::visit( UntypedMemberExpr *memberExpr ) {
                acceptNewScope( memberExpr->get_result(), *this );
                maybeAccept( memberExpr->get_aggregate(), *this );
        }

        void Indexer::visit( MemberExpr *memberExpr ) {
                acceptNewScope( memberExpr->get_result(), *this );
                maybeAccept( memberExpr->get_aggregate(), *this );
        }

        void Indexer::visit( VariableExpr *variableExpr ) {
                acceptNewScope( variableExpr->get_result(), *this );
        }

        void Indexer::visit( ConstantExpr *constantExpr ) {
                acceptNewScope( constantExpr->get_result(), *this );
                maybeAccept( constantExpr->get_constant(), *this );
        }

        void Indexer::visit( SizeofExpr *sizeofExpr ) {
                acceptNewScope( sizeofExpr->get_result(), *this );
                if ( sizeofExpr->get_isType() ) {
                        maybeAccept( sizeofExpr->get_type(), *this );
                } else {
                        maybeAccept( sizeofExpr->get_expr(), *this );
                }
        }

        void Indexer::visit( AlignofExpr *alignofExpr ) {
                acceptNewScope( alignofExpr->get_result(), *this );
                if ( alignofExpr->get_isType() ) {
                        maybeAccept( alignofExpr->get_type(), *this );
                } else {
                        maybeAccept( alignofExpr->get_expr(), *this );
                }
        }

        void Indexer::visit( UntypedOffsetofExpr *offsetofExpr ) {
                acceptNewScope( offsetofExpr->get_result(), *this );
                maybeAccept( offsetofExpr->get_type(), *this );
        }

        void Indexer::visit( OffsetofExpr *offsetofExpr ) {
                acceptNewScope( offsetofExpr->get_result(), *this );
                maybeAccept( offsetofExpr->get_type(), *this );
                maybeAccept( offsetofExpr->get_member(), *this );
        }

        void Indexer::visit( OffsetPackExpr *offsetPackExpr ) {
                acceptNewScope( offsetPackExpr->get_result(), *this );
                maybeAccept( offsetPackExpr->get_type(), *this );
        }

        void Indexer::visit( AttrExpr *attrExpr ) {
                acceptNewScope( attrExpr->get_result(), *this );
                if ( attrExpr->get_isType() ) {
                        maybeAccept( attrExpr->get_type(), *this );
                } else {
                        maybeAccept( attrExpr->get_expr(), *this );
                }
        }

        void Indexer::visit( LogicalExpr *logicalExpr ) {
                acceptNewScope( logicalExpr->get_result(), *this );
                maybeAccept( logicalExpr->get_arg1(), *this );
                maybeAccept( logicalExpr->get_arg2(), *this );
        }

        void Indexer::visit( ConditionalExpr *conditionalExpr ) {
                acceptNewScope( conditionalExpr->get_result(), *this );
                maybeAccept( conditionalExpr->get_arg1(), *this );
                maybeAccept( conditionalExpr->get_arg2(), *this );
                maybeAccept( conditionalExpr->get_arg3(), *this );
        }

        void Indexer::visit( CommaExpr *commaExpr ) {
                acceptNewScope( commaExpr->get_result(), *this );
                maybeAccept( commaExpr->get_arg1(), *this );
                maybeAccept( commaExpr->get_arg2(), *this );
        }

        void Indexer::visit( TypeExpr *typeExpr ) {
                acceptNewScope( typeExpr->get_result(), *this );
                maybeAccept( typeExpr->get_type(), *this );
        }

        void Indexer::visit( AsmExpr *asmExpr ) {
                maybeAccept( asmExpr->get_inout(), *this );
                maybeAccept( asmExpr->get_constraint(), *this );
                maybeAccept( asmExpr->get_operand(), *this );
        }

        void Indexer::visit( ImplicitCopyCtorExpr *impCpCtorExpr ) {
                acceptNewScope( impCpCtorExpr->get_result(), *this );
                maybeAccept( impCpCtorExpr->get_callExpr(), *this );
                acceptAll( impCpCtorExpr->get_tempDecls(), *this );
                acceptAll( impCpCtorExpr->get_returnDecls(), *this );
                acceptAll( impCpCtorExpr->get_dtors(), *this );
        }

        void Indexer::visit( ConstructorExpr * ctorExpr ) {
                acceptNewScope( ctorExpr->get_result(), *this );
                maybeAccept( ctorExpr->get_callExpr(), *this );
        }

        void Indexer::visit( CompoundLiteralExpr *compLitExpr ) {
                acceptNewScope( compLitExpr->get_result(), *this );
                maybeAccept( compLitExpr->get_type(), *this );
                maybeAccept( compLitExpr->get_initializer(), *this );
        }

        void Indexer::visit( UntypedValofExpr *valofExpr ) {
                acceptNewScope( valofExpr->get_result(), *this );
                maybeAccept( valofExpr->get_body(), *this );
        }

        void Indexer::visit( RangeExpr *rangeExpr ) {
                maybeAccept( rangeExpr->get_low(), *this );
                maybeAccept( rangeExpr->get_high(), *this );
        }

        void Indexer::visit( UntypedTupleExpr *tupleExpr ) {
                acceptNewScope( tupleExpr->get_result(), *this );
                acceptAll( tupleExpr->get_exprs(), *this );
        }

        void Indexer::visit( TupleExpr *tupleExpr ) {
                acceptNewScope( tupleExpr->get_result(), *this );
                acceptAll( tupleExpr->get_exprs(), *this );
        }

        void Indexer::visit( TupleIndexExpr *tupleExpr ) {
                acceptNewScope( tupleExpr->get_result(), *this );
                maybeAccept( tupleExpr->get_tuple(), *this );
        }

        void Indexer::visit( MemberTupleExpr *tupleExpr ) {
                acceptNewScope( tupleExpr->get_result(), *this );
                maybeAccept( tupleExpr->get_member(), *this );
                maybeAccept( tupleExpr->get_aggregate(), *this );
        }

        void Indexer::visit( TupleAssignExpr *tupleExpr ) {
                acceptNewScope( tupleExpr->get_result(), *this );
                maybeAccept( tupleExpr->get_stmtExpr(), *this );
        }

        void Indexer::visit( StmtExpr *stmtExpr ) {
                acceptNewScope( stmtExpr->get_result(), *this );
                maybeAccept( stmtExpr->get_statements(), *this );
                acceptAll( stmtExpr->get_returnDecls(), *this );
                acceptAll( stmtExpr->get_dtors(), *this );
        }

        void Indexer::visit( UniqueExpr *uniqueExpr ) {
                acceptNewScope( uniqueExpr->get_result(), *this );
                maybeAccept( uniqueExpr->get_expr(), *this );
        }


        void Indexer::visit( TraitInstType *contextInst ) {
                acceptAll( contextInst->get_parameters(), *this );
                acceptAll( contextInst->get_members(), *this );
        }

        void Indexer::visit( StructInstType *structInst ) {
                if ( ! lookupStruct( structInst->get_name() ) ) {
                        debugPrint( "Adding struct " << structInst->get_name() << " from implicit forward declaration" << std::endl );
                        addStruct( structInst->get_name() );
                }
                enterScope();
                acceptAll( structInst->get_parameters(), *this );
                leaveScope();
        }

        void Indexer::visit( UnionInstType *unionInst ) {
                if ( ! lookupUnion( unionInst->get_name() ) ) {
                        debugPrint( "Adding union " << unionInst->get_name() << " from implicit forward declaration" << std::endl );
                        addUnion( unionInst->get_name() );
                }
                enterScope();
                acceptAll( unionInst->get_parameters(), *this );
                leaveScope();
        }

        void Indexer::visit( ForStmt *forStmt ) {
            // for statements introduce a level of scope
            enterScope();
            Visitor::visit( forStmt );
            leaveScope();
        }



        void Indexer::lookupId( const std::string &id, std::list< DeclarationWithType* > &out ) const {
                std::unordered_set< std::string > foundMangleNames;

                Indexer::Impl *searchTables = tables;
                while ( searchTables ) {

                        IdTable::const_iterator decls = searchTables->idTable.find( id );
                        if ( decls != searchTables->idTable.end() ) {
                                const MangleTable &mangleTable = decls->second;
                                for ( MangleTable::const_iterator decl = mangleTable.begin(); decl != mangleTable.end(); ++decl ) {
                                        // mark the mangled name as found, skipping this insertion if a declaration for that name has already been found
                                        if ( foundMangleNames.insert( decl->first ).second == false ) continue;

                                        out.push_back( decl->second );
                                }
                        }

                        // get declarations from base indexers
                        searchTables = searchTables->base.tables;
                }

                // some special functions, e.g. constructors and destructors
                // remove autogenerated functions when they are defined so that
                // they can never be matched
                removeSpecialOverrides( id, out );
        }

        NamedTypeDecl *Indexer::lookupType( const std::string &id ) const {
                if ( ! tables ) return 0;

                TypeTable::const_iterator ret = tables->typeTable.find( id );
                return ret != tables->typeTable.end() ? ret->second : tables->base.lookupType( id );
        }

        StructDecl *Indexer::lookupStruct( const std::string &id ) const {
                if ( ! tables ) return 0;

                StructTable::const_iterator ret = tables->structTable.find( id );
                return ret != tables->structTable.end() ? ret->second : tables->base.lookupStruct( id );
        }

        EnumDecl *Indexer::lookupEnum( const std::string &id ) const {
                if ( ! tables ) return 0;

                EnumTable::const_iterator ret = tables->enumTable.find( id );
                return ret != tables->enumTable.end() ? ret->second : tables->base.lookupEnum( id );
        }

        UnionDecl *Indexer::lookupUnion( const std::string &id ) const {
                if ( ! tables ) return 0;

                UnionTable::const_iterator ret = tables->unionTable.find( id );
                return ret != tables->unionTable.end() ? ret->second : tables->base.lookupUnion( id );
        }

        TraitDecl *Indexer::lookupTrait( const std::string &id ) const {
                if ( ! tables ) return 0;

                TraitTable::const_iterator ret = tables->traitTable.find( id );
                return ret != tables->traitTable.end() ? ret->second : tables->base.lookupTrait( id );
        }

        DeclarationWithType *Indexer::lookupIdAtScope( const std::string &id, const std::string &mangleName, unsigned long scope ) const {
                if ( ! tables ) return 0;
                if ( tables->scope < scope ) return 0;

                IdTable::const_iterator decls = tables->idTable.find( id );
                if ( decls != tables->idTable.end() ) {
                        const MangleTable &mangleTable = decls->second;
                        MangleTable::const_iterator decl = mangleTable.find( mangleName );
                        if ( decl != mangleTable.end() ) return decl->second;
                }

                return tables->base.lookupIdAtScope( id, mangleName, scope );
        }

        bool Indexer::hasIncompatibleCDecl( const std::string &id, const std::string &mangleName, unsigned long scope ) const {
                if ( ! tables ) return false;
                if ( tables->scope < scope ) return false;

                IdTable::const_iterator decls = tables->idTable.find( id );
                if ( decls != tables->idTable.end() ) {
                        const MangleTable &mangleTable = decls->second;
                        for ( MangleTable::const_iterator decl = mangleTable.begin(); decl != mangleTable.end(); ++decl ) {
                                // check for C decls with the same name, skipping those with a compatible type (by mangleName)
                                if ( decl->second->get_linkage() == LinkageSpec::C && decl->first != mangleName ) return true;
                        }
                }

                return tables->base.hasIncompatibleCDecl( id, mangleName, scope );
        }

        bool Indexer::hasCompatibleCDecl( const std::string &id, const std::string &mangleName, unsigned long scope ) const {
                if ( ! tables ) return false;
                if ( tables->scope < scope ) return false;

                IdTable::const_iterator decls = tables->idTable.find( id );
                if ( decls != tables->idTable.end() ) {
                        const MangleTable &mangleTable = decls->second;
                        for ( MangleTable::const_iterator decl = mangleTable.begin(); decl != mangleTable.end(); ++decl ) {
                                // check for C decls with the same name, skipping
                                // those with an incompatible type (by mangleName)
                                if ( decl->second->get_linkage() == LinkageSpec::C && decl->first == mangleName ) return true;
                        }
                }

                return tables->base.hasCompatibleCDecl( id, mangleName, scope );
        }

        NamedTypeDecl *Indexer::lookupTypeAtScope( const std::string &id, unsigned long scope ) const {
                if ( ! tables ) return 0;
                if ( tables->scope < scope ) return 0;

                TypeTable::const_iterator ret = tables->typeTable.find( id );
                return ret != tables->typeTable.end() ? ret->second : tables->base.lookupTypeAtScope( id, scope );
        }

        StructDecl *Indexer::lookupStructAtScope( const std::string &id, unsigned long scope ) const {
                if ( ! tables ) return 0;
                if ( tables->scope < scope ) return 0;

                StructTable::const_iterator ret = tables->structTable.find( id );
                return ret != tables->structTable.end() ? ret->second : tables->base.lookupStructAtScope( id, scope );
        }

        EnumDecl *Indexer::lookupEnumAtScope( const std::string &id, unsigned long scope ) const {
                if ( ! tables ) return 0;
                if ( tables->scope < scope ) return 0;

                EnumTable::const_iterator ret = tables->enumTable.find( id );
                return ret != tables->enumTable.end() ? ret->second : tables->base.lookupEnumAtScope( id, scope );
        }

        UnionDecl *Indexer::lookupUnionAtScope( const std::string &id, unsigned long scope ) const {
                if ( ! tables ) return 0;
                if ( tables->scope < scope ) return 0;

                UnionTable::const_iterator ret = tables->unionTable.find( id );
                return ret != tables->unionTable.end() ? ret->second : tables->base.lookupUnionAtScope( id, scope );
        }

        TraitDecl *Indexer::lookupTraitAtScope( const std::string &id, unsigned long scope ) const {
                if ( ! tables ) return 0;
                if ( tables->scope < scope ) return 0;

                TraitTable::const_iterator ret = tables->traitTable.find( id );
                return ret != tables->traitTable.end() ? ret->second : tables->base.lookupTraitAtScope( id, scope );
        }

        bool addedIdConflicts( DeclarationWithType *existing, DeclarationWithType *added ) {
                // if we're giving the same name mangling to things of different types then there is something wrong
                assert( (dynamic_cast<ObjectDecl*>( added ) && dynamic_cast<ObjectDecl*>( existing ) )
                        || (dynamic_cast<FunctionDecl*>( added ) && dynamic_cast<FunctionDecl*>( existing ) ) );

                if ( LinkageSpec::isOverridable( existing->get_linkage() ) ) {
                        // new definition shadows the autogenerated one, even at the same scope
                        return false;
                } else if ( added->get_linkage() != LinkageSpec::C || ResolvExpr::typesCompatible( added->get_type(), existing->get_type(), Indexer() ) ) {
                        // typesCompatible doesn't really do the right thing here. When checking compatibility of function types,
                        // we should ignore outermost pointer qualifiers, except _Atomic?
                        FunctionDecl *newentry = dynamic_cast< FunctionDecl* >( added );
                        FunctionDecl *oldentry = dynamic_cast< FunctionDecl* >( existing );
                        if ( newentry && oldentry ) {
                                if ( newentry->get_statements() && oldentry->get_statements() ) {
                                        throw SemanticError( "duplicate function definition for ", added );
                                } // if
                        } else {
                                // two objects with the same mangled name defined in the same scope.
                                // both objects must be marked extern or both must be intrinsic for this to be okay
                                // xxx - perhaps it's actually if either is intrinsic then this is okay?
                                //       might also need to be same storage class?
                                ObjectDecl *newobj = dynamic_cast< ObjectDecl* >( added );
                                ObjectDecl *oldobj = dynamic_cast< ObjectDecl* >( existing );
                                if ( ! newobj->get_storageClasses()[ DeclarationNode::Extern ] && ! oldobj->get_storageClasses()[ DeclarationNode::Extern ] ) {
                                        throw SemanticError( "duplicate object definition for ", added );
                                } // if
                        } // if
                } else {
                        throw SemanticError( "duplicate definition for ", added );
                } // if

                return true;
        }

        void Indexer::addId( DeclarationWithType *decl ) {
                makeWritable();

                const std::string &name = decl->get_name();
                std::string mangleName;
                if ( LinkageSpec::isOverridable( decl->get_linkage() ) ) {
                        // mangle the name without including the appropriate suffix, so overridable routines are placed into the
                        // same "bucket" as their user defined versions.
                        mangleName = Mangler::mangle( decl, false );
                } else {
                        mangleName = Mangler::mangle( decl );
                } // if

                // this ensures that no two declarations with the same unmangled name at the same scope both have C linkage
                if ( decl->get_linkage() == LinkageSpec::C ) {
                        // NOTE this is broken in Richard's original code in such a way that it never triggers (it
                        // doesn't check decls that have the same manglename, and all C-linkage decls are defined to
                        // have their name as their manglename, hence the error can never trigger).
                        // The code here is closer to correct, but name mangling would have to be completely
                        // isomorphic to C type-compatibility, which it may not be.
                        if ( hasIncompatibleCDecl( name, mangleName, scope ) ) {
                                throw SemanticError( "conflicting overload of C function ", decl );
                        }
                } else {
                        // Check that a Cforall declaration doesn't overload any C declaration
                        if ( hasCompatibleCDecl( name, mangleName, scope ) ) {
                                throw SemanticError( "Cforall declaration hides C function ", decl );
                        }
                }

                // Skip repeat declarations of the same identifier
                DeclarationWithType *existing = lookupIdAtScope( name, mangleName, scope );
                if ( existing && addedIdConflicts( existing, decl ) ) return;

                // add to indexer
                tables->idTable[ name ][ mangleName ] = decl;
                ++tables->size;
        }

        bool addedTypeConflicts( NamedTypeDecl *existing, NamedTypeDecl *added ) {
                if ( existing->get_base() == 0 ) {
                        return false;
                } else if ( added->get_base() == 0 ) {
                        return true;
                } else {
                        throw SemanticError( "redeclaration of ", added );
                }
        }

        void Indexer::addType( NamedTypeDecl *decl ) {
                makeWritable();

                const std::string &id = decl->get_name();
                TypeTable::iterator existing = tables->typeTable.find( id );
                if ( existing == tables->typeTable.end() ) {
                        NamedTypeDecl *parent = tables->base.lookupTypeAtScope( id, scope );
                        if ( ! parent || ! addedTypeConflicts( parent, decl ) ) {
                                tables->typeTable.insert( existing, std::make_pair( id, decl ) );
                                ++tables->size;
                        }
                } else {
                        if ( ! addedTypeConflicts( existing->second, decl ) ) {
                                existing->second = decl;
                        }
                }
        }

        bool addedDeclConflicts( AggregateDecl *existing, AggregateDecl *added ) {
                if ( existing->get_members().empty() ) {
                        return false;
                } else if ( ! added->get_members().empty() ) {
                        throw SemanticError( "redeclaration of ", added );
                } // if
                return true;
        }

        void Indexer::addStruct( const std::string &id ) {
                addStruct( new StructDecl( id ) );
        }

        void Indexer::addStruct( StructDecl *decl ) {
                makeWritable();

                const std::string &id = decl->get_name();
                StructTable::iterator existing = tables->structTable.find( id );
                if ( existing == tables->structTable.end() ) {
                        StructDecl *parent = tables->base.lookupStructAtScope( id, scope );
                        if ( ! parent || ! addedDeclConflicts( parent, decl ) ) {
                                tables->structTable.insert( existing, std::make_pair( id, decl ) );
                                ++tables->size;
                        }
                } else {
                        if ( ! addedDeclConflicts( existing->second, decl ) ) {
                                existing->second = decl;
                        }
                }
        }

        void Indexer::addEnum( EnumDecl *decl ) {
                makeWritable();

                const std::string &id = decl->get_name();
                EnumTable::iterator existing = tables->enumTable.find( id );
                if ( existing == tables->enumTable.end() ) {
                        EnumDecl *parent = tables->base.lookupEnumAtScope( id, scope );
                        if ( ! parent || ! addedDeclConflicts( parent, decl ) ) {
                                tables->enumTable.insert( existing, std::make_pair( id, decl ) );
                                ++tables->size;
                        }
                } else {
                        if ( ! addedDeclConflicts( existing->second, decl ) ) {
                                existing->second = decl;
                        }
                }
        }

        void Indexer::addUnion( const std::string &id ) {
                addUnion( new UnionDecl( id ) );
        }

        void Indexer::addUnion( UnionDecl *decl ) {
                makeWritable();

                const std::string &id = decl->get_name();
                UnionTable::iterator existing = tables->unionTable.find( id );
                if ( existing == tables->unionTable.end() ) {
                        UnionDecl *parent = tables->base.lookupUnionAtScope( id, scope );
                        if ( ! parent || ! addedDeclConflicts( parent, decl ) ) {
                                tables->unionTable.insert( existing, std::make_pair( id, decl ) );
                                ++tables->size;
                        }
                } else {
                        if ( ! addedDeclConflicts( existing->second, decl ) ) {
                                existing->second = decl;
                        }
                }
        }

        void Indexer::addTrait( TraitDecl *decl ) {
                makeWritable();

                const std::string &id = decl->get_name();
                TraitTable::iterator existing = tables->traitTable.find( id );
                if ( existing == tables->traitTable.end() ) {
                        TraitDecl *parent = tables->base.lookupTraitAtScope( id, scope );
                        if ( ! parent || ! addedDeclConflicts( parent, decl ) ) {
                                tables->traitTable.insert( existing, std::make_pair( id, decl ) );
                                ++tables->size;
                        }
                } else {
                        if ( ! addedDeclConflicts( existing->second, decl ) ) {
                                existing->second = decl;
                        }
                }
        }

        void Indexer::enterScope() {
                ++scope;

                if ( doDebug ) {
                        std::cout << "--- Entering scope " << scope << std::endl;
                }
        }

        void Indexer::leaveScope() {
                using std::cout;

                assert( scope > 0 && "cannot leave initial scope" );
                --scope;

                while ( tables && tables->scope > scope ) {
                        if ( doDebug ) {
                                cout << "--- Leaving scope " << tables->scope << " containing" << std::endl;
                                dump( tables->idTable, cout );
                                dump( tables->typeTable, cout );
                                dump( tables->structTable, cout );
                                dump( tables->enumTable, cout );
                                dump( tables->unionTable, cout );
                                dump( tables->traitTable, cout );
                        }

                        // swap tables for base table until we find one at an appropriate scope
                        Indexer::Impl *base = newRef( tables->base.tables );
                        deleteRef( tables );
                        tables = base;
                }
        }

        void Indexer::print( std::ostream &os, int indent ) const {
            using std::cerr;

                if ( tables ) {
                        os << "--- scope " << tables->scope << " ---" << std::endl;

                        os << "===idTable===" << std::endl;
                        dump( tables->idTable, os );
                        os << "===typeTable===" << std::endl;
                        dump( tables->typeTable, os );
                        os << "===structTable===" << std::endl;
                        dump( tables->structTable, os );
                        os << "===enumTable===" << std::endl;
                        dump( tables->enumTable, os );
                        os << "===unionTable===" << std::endl;
                        dump( tables->unionTable, os );
                        os << "===contextTable===" << std::endl;
                        dump( tables->traitTable, os );

                        tables->base.print( os, indent );
                } else {
                        os << "--- end ---" << std::endl;
                }

        }
} // namespace SymTab

// Local Variables: //
// tab-width: 4 //
// mode: c++ //
// compile-command: "make install" //
// End: //