source: src/InitTweak/FixInit.cc @ 1bc1bb2

//
// 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.
//
// FixInit.h --
//
// Author           : Rob Schluntz
// Created On       : Wed Jan 13 16:29:30 2016
// Last Modified By : Rob Schluntz
// Last Modified On : Fri May 13 11:44:26 2016
// Update Count     : 30
//

#include <stack>
#include <list>
#include <iterator>
#include <algorithm>
#include "FixInit.h"
#include "InitTweak.h"
#include "ResolvExpr/Resolver.h"
#include "ResolvExpr/typeops.h"
#include "SynTree/Declaration.h"
#include "SynTree/Type.h"
#include "SynTree/Expression.h"
#include "SynTree/Statement.h"
#include "SynTree/Initializer.h"
#include "SynTree/Mutator.h"
#include "SymTab/Indexer.h"
#include "GenPoly/PolyMutator.h"
#include "SynTree/AddStmtVisitor.h"

bool ctordtorp = false;
bool ctorp = false;
bool cpctorp = false;
bool dtorp = false;
#define PRINT( text ) if ( ctordtorp ) { text }
#define CP_CTOR_PRINT( text ) if ( ctordtorp || cpctorp ) { text }
#define DTOR_PRINT( text ) if ( ctordtorp || dtorp ) { text }

namespace InitTweak {
        namespace {
                const std::list<Label> noLabels;
                const std::list<Expression*> noDesignators;

                class InsertImplicitCalls : public GenPoly::PolyMutator {
                public:
                        /// wrap function application expressions as ImplicitCopyCtorExpr nodes
                        /// so that it is easy to identify which function calls need their parameters
                        /// to be copy constructed
                        static void insert( std::list< Declaration * > & translationUnit );

                        virtual Expression * mutate( ApplicationExpr * appExpr );
                };

                class ResolveCopyCtors : public SymTab::Indexer {
                public:
                        /// generate temporary ObjectDecls for each argument and return value of each
                        /// ImplicitCopyCtorExpr, generate/resolve copy construction expressions for each,
                        /// and generate/resolve destructors for both arguments and return value temporaries
                        static void resolveImplicitCalls( std::list< Declaration * > & translationUnit );

                        virtual void visit( ImplicitCopyCtorExpr * impCpCtorExpr );

                        /// create and resolve ctor/dtor expression: fname(var, [cpArg])
                        ApplicationExpr * makeCtorDtor( const std::string & fname, ObjectDecl * var, Expression * cpArg = NULL );
                        /// true if type does not need to be copy constructed to ensure correctness
                        bool skipCopyConstruct( Type * );
                private:
                        TypeSubstitution * env;
                };

                /// collects constructed object decls - used as a base class
                class ObjDeclCollector : public AddStmtVisitor {
                  public:
                        typedef AddStmtVisitor Parent;
                        using Parent::visit;
                        typedef std::set< ObjectDecl * > ObjectSet;
                        virtual void visit( CompoundStmt *compoundStmt );
                        virtual void visit( DeclStmt *stmt );
                  protected:
                        ObjectSet curVars;
                };

                struct printSet {
                        typedef ObjDeclCollector::ObjectSet ObjectSet;
                        printSet( const ObjectSet & objs ) : objs( objs ) {}
                        const ObjectSet & objs;
                };
                std::ostream & operator<<( std::ostream & out, const printSet & set) {
                        out << "{ ";
                        for ( ObjectDecl * obj : set.objs ) {
                                out << obj->get_name() << ", " ;
                        }
                        out << " }";
                        return out;
                }

                class LabelFinder : public ObjDeclCollector {
                  public:
                        typedef ObjDeclCollector Parent;
                        typedef std::map< Label, ObjectSet > LabelMap;
                        // map of Label -> live variables at that label
                        LabelMap vars;

                        void handleStmt( Statement * stmt );

                        // xxx - This needs to be done better.
                        // allow some generalization among different kinds of nodes with
                        // with similar parentage (e.g. all expressions, all statements, etc.)
                        // important to have this to provide a single entry point so that as
                        // new subclasses are added, there is only one place that the code has
                        // to be updated, rather than ensure that every specialized class knows
                        // about every new kind of statement that might be added.
                        virtual void visit( CompoundStmt *stmt ) { handleStmt( stmt ); return Parent::visit( stmt ); }
                        virtual void visit( ExprStmt *stmt ) { handleStmt( stmt ); return Parent::visit( stmt ); }
                        virtual void visit( AsmStmt *stmt ) { handleStmt( stmt ); return Parent::visit( stmt ); }
                        virtual void visit( IfStmt *stmt ) { handleStmt( stmt ); return Parent::visit( stmt ); }
                        virtual void visit( WhileStmt *stmt ) { handleStmt( stmt ); return Parent::visit( stmt ); }
                        virtual void visit( ForStmt *stmt ) { handleStmt( stmt ); return Parent::visit( stmt ); }
                        virtual void visit( SwitchStmt *stmt ) { handleStmt( stmt ); return Parent::visit( stmt ); }
                        virtual void visit( ChooseStmt *stmt ) { handleStmt( stmt ); return Parent::visit( stmt ); }
                        virtual void visit( FallthruStmt *stmt ) { handleStmt( stmt ); return Parent::visit( stmt ); }
                        virtual void visit( CaseStmt *stmt ) { handleStmt( stmt ); return Parent::visit( stmt ); }
                        virtual void visit( BranchStmt *stmt ) { handleStmt( stmt ); return Parent::visit( stmt ); }
                        virtual void visit( ReturnStmt *stmt ) { handleStmt( stmt ); return Parent::visit( stmt ); }
                        virtual void visit( TryStmt *stmt ) { handleStmt( stmt ); return Parent::visit( stmt ); }
                        virtual void visit( CatchStmt *stmt ) { handleStmt( stmt ); return Parent::visit( stmt ); }
                        virtual void visit( FinallyStmt *stmt ) { handleStmt( stmt ); return Parent::visit( stmt ); }
                        virtual void visit( NullStmt *stmt ) { handleStmt( stmt ); return Parent::visit( stmt ); }
                        virtual void visit( DeclStmt *stmt ) { handleStmt( stmt ); return Parent::visit( stmt ); }
                        virtual void visit( ImplicitCtorDtorStmt *stmt ) { handleStmt( stmt ); return Parent::visit( stmt ); }
                };

                class InsertDtors : public ObjDeclCollector {
                public:
                        /// insert destructor calls at the appropriate places.
                        /// must happen before CtorInit nodes are removed (currently by FixInit)
                        static void insert( std::list< Declaration * > & translationUnit );

                        typedef ObjDeclCollector Parent;
                        typedef std::list< ObjectDecl * > OrderedDecls;
                        typedef std::list< OrderedDecls > OrderedDeclsStack;

                        InsertDtors( LabelFinder & finder ) : labelVars( finder.vars ) {}

                        virtual void visit( ObjectDecl * objDecl );

                        virtual void visit( CompoundStmt * compoundStmt );
                        virtual void visit( ReturnStmt * returnStmt );
                        virtual void visit( BranchStmt * stmt );
                private:
                        void handleGoto( BranchStmt * stmt );

                        LabelFinder::LabelMap & labelVars;
                        OrderedDeclsStack reverseDeclOrder;
                };

                class FixInit : public GenPoly::PolyMutator {
                  public:
                        /// expand each object declaration to use its constructor after it is declared.
                        static void fixInitializers( std::list< Declaration * > &translationUnit );

                        virtual DeclarationWithType * mutate( ObjectDecl *objDecl );
                };

                class FixCopyCtors : public GenPoly::PolyMutator {
                  public:
                        /// expand ImplicitCopyCtorExpr nodes into the temporary declarations, copy constructors,
                        /// call expression, and destructors
                        static void fixCopyCtors( std::list< Declaration * > &translationUnit );

                        virtual Expression * mutate( ImplicitCopyCtorExpr * impCpCtorExpr );
                };
        } // namespace

        void fix( std::list< Declaration * > & translationUnit ) {
                InsertImplicitCalls::insert( translationUnit );
                ResolveCopyCtors::resolveImplicitCalls( translationUnit );
                InsertDtors::insert( translationUnit );
                FixInit::fixInitializers( translationUnit );

                // FixCopyCtors must happen after FixInit, so that destructors are placed correctly
                FixCopyCtors::fixCopyCtors( translationUnit );
        }

        namespace {
                void InsertImplicitCalls::insert( std::list< Declaration * > & translationUnit ) {
                        InsertImplicitCalls inserter;
                        mutateAll( translationUnit, inserter );
                }

                void ResolveCopyCtors::resolveImplicitCalls( std::list< Declaration * > & translationUnit ) {
                        ResolveCopyCtors resolver;
                        acceptAll( translationUnit, resolver );
                }

                void FixInit::fixInitializers( std::list< Declaration * > & translationUnit ) {
                        FixInit fixer;
                        mutateAll( translationUnit, fixer );
                }

                void InsertDtors::insert( std::list< Declaration * > & translationUnit ) {
                        LabelFinder finder;
                        InsertDtors inserter( finder );
                        acceptAll( translationUnit, finder );
                        acceptAll( translationUnit, inserter );
                }

                void FixCopyCtors::fixCopyCtors( std::list< Declaration * > & translationUnit ) {
                        FixCopyCtors fixer;
                        mutateAll( translationUnit, fixer );
                }

                Expression * InsertImplicitCalls::mutate( ApplicationExpr * appExpr ) {
                        appExpr = dynamic_cast< ApplicationExpr * >( Mutator::mutate( appExpr ) );
                        assert( appExpr );

                        if ( VariableExpr * function = dynamic_cast< VariableExpr * > ( appExpr->get_function() ) ) {
                                if ( function->get_var()->get_linkage() == LinkageSpec::Intrinsic ) {
                                        // optimization: don't need to copy construct in order to call intrinsic functions
                                        return appExpr;
                                } else if ( DeclarationWithType * funcDecl = dynamic_cast< DeclarationWithType * > ( function->get_var() ) ) {
                                        FunctionType * ftype = dynamic_cast< FunctionType * >( GenPoly::getFunctionType( funcDecl->get_type() ) );
                                        assert( ftype );
                                        if ( (funcDecl->get_name() == "?{}" || funcDecl->get_name() == "?=?") && ftype->get_parameters().size() == 2 ) {
                                                Type * t1 = ftype->get_parameters().front()->get_type();
                                                Type * t2 = ftype->get_parameters().back()->get_type();
                                                PointerType * ptrType = dynamic_cast< PointerType * > ( t1 );
                                                assert( ptrType );

                                                if ( ResolvExpr::typesCompatible( ptrType->get_base(), t2, SymTab::Indexer() ) ) {
                                                        // optimization: don't need to copy construct in order to call a copy constructor or
                                                        // assignment operator
                                                        return appExpr;
                                                }
                                        } else if ( funcDecl->get_name() == "^?{}" ) {
                                                // correctness: never copy construct arguments to a destructor
                                                return appExpr;
                                        }
                                }
                        }
                        CP_CTOR_PRINT( std::cerr << "InsertImplicitCalls: adding a wrapper " << appExpr << std::endl; )

                        // wrap each function call so that it is easy to identify nodes that have to be copy constructed
                        ImplicitCopyCtorExpr * expr = new ImplicitCopyCtorExpr( appExpr );
                        // save the type substitution onto the new node so that it is easy to find.
                        // Ensure it is not deleted with the ImplicitCopyCtorExpr by removing it before deletion.
                        // The substitution is needed to obtain the type of temporary variables so that copy constructor
                        // calls can be resolved. Normally this is what PolyMutator is for, but the pass that resolves
                        // copy constructor calls must be an Indexer. We could alternatively make a PolyIndexer which
                        // saves the environment, or compute the types of temporaries here, but it's much simpler to
                        // save the environment here, and more cohesive to compute temporary variables and resolve copy
                        // constructor calls together.
                        assert( env );
                        expr->set_env( env );
                        return expr;
                }

                bool ResolveCopyCtors::skipCopyConstruct( Type * type ) {
                        return dynamic_cast< VarArgsType * >( type ) || GenPoly::getFunctionType( type );
                }

                ApplicationExpr * ResolveCopyCtors::makeCtorDtor( const std::string & fname, ObjectDecl * var, Expression * cpArg ) {
                        assert( var );
                        UntypedExpr * untyped = new UntypedExpr( new NameExpr( fname ) );
                        untyped->get_args().push_back( new AddressExpr( new VariableExpr( var ) ) );
                        if (cpArg) untyped->get_args().push_back( cpArg );

                        // resolve copy constructor
                        // should only be one alternative for copy ctor and dtor expressions, since
                        // all arguments are fixed (VariableExpr and already resolved expression)
                        CP_CTOR_PRINT( std::cerr << "ResolvingCtorDtor " << untyped << std::endl; )
                        ApplicationExpr * resolved = dynamic_cast< ApplicationExpr * >( ResolvExpr::findVoidExpression( untyped, *this ) );
                        if ( resolved->get_env() ) {
                                env->add( *resolved->get_env() );
                        }

                        assert( resolved );
                        delete untyped;
                        return resolved;
                }

                void ResolveCopyCtors::visit( ImplicitCopyCtorExpr *impCpCtorExpr ) {
                        static UniqueName tempNamer("_tmp_cp");
                        static UniqueName retNamer("_tmp_cp_ret");

                        CP_CTOR_PRINT( std::cerr << "ResolveCopyCtors: " << impCpCtorExpr << std::endl; )
                        Visitor::visit( impCpCtorExpr );
                        env = impCpCtorExpr->get_env(); // xxx - maybe we really should just have a PolyIndexer...

                        ApplicationExpr * appExpr = impCpCtorExpr->get_callExpr();

                        // take each argument and attempt to copy construct it.
                        for ( Expression * & arg : appExpr->get_args() ) {
                                CP_CTOR_PRINT( std::cerr << "Type Substitution: " << *impCpCtorExpr->get_env() << std::endl; )
                                // xxx - need to handle tuple arguments
                                assert( ! arg->get_results().empty() );
                                Type * result = arg->get_results().front();
                                if ( skipCopyConstruct( result ) ) continue; // skip certain non-copyable types
                                // type may involve type variables, so apply type substitution to get temporary variable's actual type
                                result = result->clone();
                                impCpCtorExpr->get_env()->apply( result );
                                ObjectDecl * tmp = new ObjectDecl( tempNamer.newName(), DeclarationNode::NoStorageClass, LinkageSpec::C, 0, result, 0 );
                                tmp->get_type()->set_isConst( false );

                                // create and resolve copy constructor
                                CP_CTOR_PRINT( std::cerr << "makeCtorDtor for an argument" << std::endl; )
                                ApplicationExpr * cpCtor = makeCtorDtor( "?{}", tmp, arg );

                                // if the chosen constructor is intrinsic, the copy is unnecessary, so
                                // don't create the temporary and don't call the copy constructor
                                VariableExpr * function = dynamic_cast< VariableExpr * >( cpCtor->get_function() );
                                assert( function );
                                if ( function->get_var()->get_linkage() != LinkageSpec::Intrinsic ) {
                                        // replace argument to function call with temporary
                                        arg = new CommaExpr( cpCtor, new VariableExpr( tmp ) );
                                        impCpCtorExpr->get_tempDecls().push_back( tmp );
                                        impCpCtorExpr->get_dtors().push_front( makeCtorDtor( "^?{}", tmp ) );
                                }
                        }

                        // each return value from the call needs to be connected with an ObjectDecl
                        // at the call site, which is initialized with the return value and is destructed
                        // later
                        // xxx - handle multiple return values
                        ApplicationExpr * callExpr = impCpCtorExpr->get_callExpr();
                        // xxx - is this right? callExpr may not have the right environment, because it was attached
                        // at a higher level. Trying to pass that environment along.
                        callExpr->set_env( impCpCtorExpr->get_env()->clone() );
                        for ( Type * result : appExpr->get_results() ) {
                                result = result->clone();
                                impCpCtorExpr->get_env()->apply( result );
                                ObjectDecl * ret = new ObjectDecl( retNamer.newName(), DeclarationNode::NoStorageClass, LinkageSpec::C, 0, result, 0 );
                                ret->get_type()->set_isConst( false );
                                impCpCtorExpr->get_returnDecls().push_back( ret );
                                CP_CTOR_PRINT( std::cerr << "makeCtorDtor for a return" << std::endl; )
                                impCpCtorExpr->get_dtors().push_front( makeCtorDtor( "^?{}", ret ) );
                        }
                        CP_CTOR_PRINT( std::cerr << "after Resolving: " << impCpCtorExpr << std::endl; )
                }


                Expression * FixCopyCtors::mutate( ImplicitCopyCtorExpr * impCpCtorExpr ) {
                        CP_CTOR_PRINT( std::cerr << "FixCopyCtors: " << impCpCtorExpr << std::endl; )

                        impCpCtorExpr = dynamic_cast< ImplicitCopyCtorExpr * >( Mutator::mutate( impCpCtorExpr ) );
                        assert( impCpCtorExpr );

                        std::list< ObjectDecl * > & tempDecls = impCpCtorExpr->get_tempDecls();
                        std::list< ObjectDecl * > & returnDecls = impCpCtorExpr->get_returnDecls();
                        std::list< Expression * > & dtors = impCpCtorExpr->get_dtors();

                        // add all temporary declarations and their constructors
                        for ( ObjectDecl * obj : tempDecls ) {
                                stmtsToAdd.push_back( new DeclStmt( noLabels, obj ) );
                        }
                        for ( ObjectDecl * obj : returnDecls ) {
                                stmtsToAdd.push_back( new DeclStmt( noLabels, obj ) );
                        }

                        // add destructors after current statement
                        for ( Expression * dtor : dtors ) {
                                stmtsToAddAfter.push_back( new ExprStmt( noLabels, dtor ) );
                        }

                        // xxx - update to work with multiple return values
                        ObjectDecl * returnDecl = returnDecls.empty() ? NULL : returnDecls.front();
                        Expression * callExpr = impCpCtorExpr->get_callExpr();

                        CP_CTOR_PRINT( std::cerr << "Coming out the back..." << impCpCtorExpr << std::endl; )

                        // detach fields from wrapper node so that it can be deleted without deleting too much
                        dtors.clear();
                        tempDecls.clear();
                        returnDecls.clear();
                        impCpCtorExpr->set_callExpr( NULL );
                        impCpCtorExpr->set_env( NULL );
                        delete impCpCtorExpr;

                        if ( returnDecl ) {
                                UntypedExpr * assign = new UntypedExpr( new NameExpr( "?=?" ) );
                                assign->get_args().push_back( new VariableExpr( returnDecl ) );
                                assign->get_args().push_back( callExpr );
                                // know the result type of the assignment is the type of the LHS (minus the pointer), so
                                // add that onto the assignment expression so that later steps have the necessary information
                                assign->add_result( returnDecl->get_type()->clone() );

                                Expression * retExpr = new CommaExpr( assign, new VariableExpr( returnDecl ) );
                                if ( callExpr->get_results().front()->get_isLvalue() ) {
                                        // lvalue returning functions are funny. Lvalue.cc inserts a *? in front of any
                                        // lvalue returning non-intrinsic function. Add an AddressExpr to the call to negate
                                        // the derefence and change the type of the return temporary from T to T* to properly
                                        // capture the return value. Then dereference the result of the comma expression, since
                                        // the lvalue returning call was originally wrapped with an AddressExpr.
                                        // Effectively, this turns
                                        //   lvalue T f();
                                        //   &*f()
                                        // into
                                        //   T * tmp_cp_retN;
                                        //   tmp_cp_ret_N = &*(tmp_cp_ret_N = &*f(), tmp_cp_ret);
                                        // which work out in terms of types, but is pretty messy. It would be nice to find a better way.
                                        assign->get_args().back() = new AddressExpr( assign->get_args().back() );

                                        Type * resultType = returnDecl->get_type()->clone();
                                        returnDecl->set_type( new PointerType( Type::Qualifiers(), returnDecl->get_type() ) );
                                        UntypedExpr * deref = new UntypedExpr( new NameExpr( "*?" ) );
                                        deref->get_args().push_back( retExpr );
                                        deref->add_result( resultType );
                                        retExpr = deref;
                                }
                                // xxx - might need to set env on retExpr...
                                // retExpr->set_env( env->clone() );
                                return retExpr;
                        } else {
                                return callExpr;
                        }
                }

                DeclarationWithType *FixInit::mutate( ObjectDecl *objDecl ) {
                        // first recursively handle pieces of ObjectDecl so that they aren't missed by other visitors
                        // when the init is removed from the ObjectDecl
                        objDecl = dynamic_cast< ObjectDecl * >( Mutator::mutate( objDecl ) );

                        if ( ConstructorInit * ctorInit = dynamic_cast< ConstructorInit * >( objDecl->get_init() ) ) {
                                // a decision should have been made by the resolver, so ctor and init are not both non-NULL
                                assert( ! ctorInit->get_ctor() || ! ctorInit->get_init() );
                                if ( Statement * ctor = ctorInit->get_ctor() ) {
                                        if ( objDecl->get_storageClass() == DeclarationNode::Static ) {
                                                // generate:
                                                // static bool __objName_uninitialized = true;
                                                // if (__objName_uninitialized) {
                                                //   __ctor(__objName);
                                                //   void dtor_atexit() {
                                                //     __dtor(__objName);
                                                //   }
                                                //   on_exit(dtorOnExit, &__objName);
                                                //   __objName_uninitialized = false;
                                                // }

                                                // generate first line
                                                BasicType * boolType = new BasicType( Type::Qualifiers(), BasicType::Bool );
                                                SingleInit * boolInitExpr = new SingleInit( new ConstantExpr( Constant( boolType->clone(), "1" ) ), noDesignators );
                                                ObjectDecl * isUninitializedVar = new ObjectDecl( objDecl->get_mangleName() + "_uninitialized", DeclarationNode::Static, LinkageSpec::Cforall, 0, boolType, boolInitExpr );
                                                isUninitializedVar->fixUniqueId();

                                                // void dtor_atexit(...) {...}
                                                FunctionDecl * dtorCaller = new FunctionDecl( objDecl->get_mangleName() + "_dtor_atexit", DeclarationNode::NoStorageClass, LinkageSpec::C, new FunctionType( Type::Qualifiers(), false ), new CompoundStmt( noLabels ), false, false );
                                                dtorCaller->fixUniqueId();
                                                dtorCaller->get_statements()->get_kids().push_back( ctorInit->get_dtor() );

                                                // on_exit(dtor_atexit);
                                                UntypedExpr * callAtexit = new UntypedExpr( new NameExpr( "atexit" ) );
                                                callAtexit->get_args().push_back( new VariableExpr( dtorCaller ) );

                                                // __objName_uninitialized = false;
                                                UntypedExpr * setTrue = new UntypedExpr( new NameExpr( "?=?" ) );
                                                setTrue->get_args().push_back( new VariableExpr( isUninitializedVar ) );
                                                setTrue->get_args().push_back( new ConstantExpr( Constant( boolType->clone(), "0" ) ) );

                                                // generate body of if
                                                CompoundStmt * initStmts = new CompoundStmt( noLabels );
                                                std::list< Statement * > & body = initStmts->get_kids();
                                                body.push_back( ctor );
                                                body.push_back( new DeclStmt( noLabels, dtorCaller ) );
                                                body.push_back( new ExprStmt( noLabels, callAtexit ) );
                                                body.push_back( new ExprStmt( noLabels, setTrue ) );

                                                // put it all together
                                                IfStmt * ifStmt = new IfStmt( noLabels, new VariableExpr( isUninitializedVar ), initStmts, 0 );
                                                stmtsToAddAfter.push_back( new DeclStmt( noLabels, isUninitializedVar ) );
                                                stmtsToAddAfter.push_back( ifStmt );
                                        } else {
                                                stmtsToAddAfter.push_back( ctor );
                                        }
                                        objDecl->set_init( NULL );
                                        ctorInit->set_ctor( NULL );
                                } else if ( Initializer * init = ctorInit->get_init() ) {
                                        objDecl->set_init( init );
                                        ctorInit->set_init( NULL );
                                } else {
                                        // no constructor and no initializer, which is okay
                                        objDecl->set_init( NULL );
                                }
                                delete ctorInit;
                        }
                        return objDecl;
                }

                void ObjDeclCollector::visit( CompoundStmt *compoundStmt ) {
                        std::set< ObjectDecl * > prevVars = curVars;
                        Parent::visit( compoundStmt );
                        curVars = prevVars;
                }

                void ObjDeclCollector::visit( DeclStmt *stmt ) {
                        // keep track of all variables currently in scope
                        if ( ObjectDecl * objDecl = dynamic_cast< ObjectDecl * > ( stmt->get_decl() ) ) {
                                curVars.insert( objDecl );
                        }
                        Parent::visit( stmt );
                }

                void LabelFinder::handleStmt( Statement * stmt ) {
                        // for each label, remember the variables in scope at that label.
                        for ( Label l : stmt->get_labels() ) {
                                vars[l] = curVars;
                        }
                }

                template<typename Iterator, typename OutputIterator>
                void insertDtors( Iterator begin, Iterator end, OutputIterator out ) {
                        for ( Iterator it = begin ; it != end ; ++it ) {
                                // extract destructor statement from the object decl and
                                // insert it into the output. Note that this is only called
                                // on lists of non-static objects with implicit non-intrinsic
                                // dtors, so if the user manually calls an intrinsic dtor
                                // then the call must (and will) still be generated since
                                // the argument may contain side effects.
                                ObjectDecl * objDecl = *it;
                                ConstructorInit * ctorInit = dynamic_cast< ConstructorInit * >( objDecl->get_init() );
                                assert( ctorInit && ctorInit->get_dtor() );
                                *out++ = ctorInit->get_dtor()->clone();
                        }
                }

                void InsertDtors::visit( ObjectDecl * objDecl ) {
                        // remember non-static destructed objects so that their destructors can be inserted later
                        if ( objDecl->get_storageClass() != DeclarationNode::Static ) {
                                if ( ConstructorInit * ctorInit = dynamic_cast< ConstructorInit * >( objDecl->get_init() ) ) {
                                        // a decision should have been made by the resolver, so ctor and init are not both non-NULL
                                        assert( ! ctorInit->get_ctor() || ! ctorInit->get_init() );
                                        Statement * dtor = ctorInit->get_dtor();
                                        if ( dtor && ! isInstrinsicSingleArgCallStmt( dtor ) ) {
                                                // don't need to call intrinsic dtor, because it does nothing, but
                                                // non-intrinsic dtors must be called
                                                reverseDeclOrder.front().push_front( objDecl );
                                        }
                                }
                        }
                        Parent::visit( objDecl );
                }

                void InsertDtors::visit( CompoundStmt * compoundStmt ) {
                        // visit statements - this will also populate reverseDeclOrder list.
                        // don't want to dump all destructors when block is left,
                        // just the destructors associated with variables defined in this block,
                        // so push a new list to the top of the stack so that we can differentiate scopes
                        reverseDeclOrder.push_front( OrderedDecls() );
                        Parent::visit( compoundStmt );

                        // add destructors for the current scope that we're exiting
                        std::list< Statement * > & statements = compoundStmt->get_kids();
                        insertDtors( reverseDeclOrder.front().begin(), reverseDeclOrder.front().end(), back_inserter( statements ) );
                        reverseDeclOrder.pop_front();
                }

                void InsertDtors::visit( ReturnStmt * returnStmt ) {
                        // return exits all scopes, so dump destructors for all scopes
                        for ( OrderedDecls & od : reverseDeclOrder ) {
                                insertDtors( od.begin(), od.end(), back_inserter( stmtsToAdd ) );
                        }
                }

                // Handle break/continue/goto in the same manner as C++.
                // Basic idea: any objects that are in scope at the BranchStmt
                // but not at the labelled (target) statement must be destructed.
                // If there are any objects in scope at the target location but
                // not at the BranchStmt then those objects would be uninitialized
                // so notify the user of the error.
                // See C++ Reference 6.6 Jump Statements for details.
                void InsertDtors::handleGoto( BranchStmt * stmt ) {
                        assert( stmt->get_target() != "" && "BranchStmt missing a label" );
                        // S_L = lvars = set of objects in scope at label definition
                        // S_G = curVars = set of objects in scope at goto statement
                        ObjectSet & lvars = labelVars[ stmt->get_target() ];

                        DTOR_PRINT(
                                std::cerr << "at goto label: " << stmt->get_target().get_name() << std::endl;
                                std::cerr << "S_G = " << printSet( curVars ) << std::endl;
                                std::cerr << "S_L = " << printSet( lvars ) << std::endl;
                        )

                        ObjectSet diff;
                        // S_L-S_G results in set of objects whose construction is skipped - it's an error if this set is non-empty
                        std::set_difference( lvars.begin(), lvars.end(), curVars.begin(), curVars.end(), std::inserter( diff, diff.begin() ) );
                        DTOR_PRINT(
                                std::cerr << "S_L-S_G = " << printSet( diff ) << std::endl;
                        )
                        if ( ! diff.empty() ) {
                                throw SemanticError( std::string("jump to label '") + stmt->get_target().get_name() + "' crosses initialization of " + (*diff.begin())->get_name() + " ", stmt );
                        }
                        // S_G-S_L results in set of objects that must be destructed
                        diff.clear();
                        std::set_difference( curVars.begin(), curVars.end(), lvars.begin(), lvars.end(), std::inserter( diff, diff.end() ) );
                        DTOR_PRINT(
                                std::cerr << "S_G-S_L = " << printSet( diff ) << std::endl;
                        )
                        if ( ! diff.empty() ) {
                                // go through decl ordered list of objectdecl. for each element that occurs in diff, output destructor
                                OrderedDecls ordered;
                                for ( OrderedDecls & rdo : reverseDeclOrder ) {
                                        // add elements from reverseDeclOrder into ordered if they occur in diff - it is key that this happens in reverse declaration order.
                                        copy_if( rdo.begin(), rdo.end(), back_inserter( ordered ), [&]( ObjectDecl * objDecl ) { return diff.count( objDecl ); } );
                                }
                                insertDtors( ordered.begin(), ordered.end(), back_inserter( stmtsToAdd ) );
                        }
                }

                void InsertDtors::visit( BranchStmt * stmt ) {
                        switch( stmt->get_type() ) {
                                case BranchStmt::Continue:
                                case BranchStmt::Break:
                                // could optimize the break/continue case, because the S_L-S_G check
                                // is unnecessary (this set should always be empty), but it serves
                                // as a small sanity check.
                                case BranchStmt::Goto:
                                        handleGoto( stmt );
                                        break;
                                default:
                                        assert( false );
                        }
                }
        } // namespace
} // namespace InitTweak

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