Changes in / [2a9d12d:381bea6]

Files:

• libcfa/prelude/builtins.c (modified) (1 diff)
• src/ControlStruct/ExceptTranslate.cc (modified) (1 diff)
• src/InitTweak/FixInit.cc (modified) (13 diffs)
• src/InitTweak/InitTweak.cc (modified) (1 diff)
• src/SymTab/Autogen.cc (modified) (5 diffs)
• src/SymTab/Autogen.h (modified) (1 diff)
• src/SynTree/DeclReplacer.cc (modified) (3 diffs)
• src/SynTree/DeclReplacer.h (modified) (1 diff)
• tests/raii/.expect/memberCtors.txt (modified) (3 diffs)
• tests/raii/memberCtors.c (modified) (2 diffs)

libcfa/prelude/builtins.c

@@ -111 +111 @@
 static inline unsigned int ?\=?( unsigned int & x, unsigned long int y ) { x = x \ y; return x; }
 
+// type that wraps a pointer and a destructor-like function - used in generating implicit destructor calls for struct members in user-defined functions
+forall(dtype T)
+struct __Destructor {
+  T * object;
+  void (*dtor)(T *);
+};
+
+// defined destructor in the case that non-generated code wants to use __Destructor
+forall(dtype T)
+static inline void ^?{}(__Destructor(T) & x) {
+        if (x.object && x.dtor) {
+          x.dtor(x.object);
+        }
+}
+
+// easy interface into __Destructor's destructor for easy codegen purposes
+extern "C" {
+  forall(dtype T)
+  static inline void __destroy_Destructor(__Destructor(T) * dtor) {
+    ^(*dtor){};
+  }
+}
+
 // Local Variables: //
 // mode: c //

src/ControlStruct/ExceptTranslate.cc

@@ -319 +319 @@
                         }
 
-                        block->push_back( handler->get_body() );
-                        handler->set_body( nullptr );
+                        block->push_back( handler->body );
+                        handler->body = nullptr;
 
                         std::list<Statement *> caseBody

src/InitTweak/FixInit.cc

@@ -54 +54 @@
 #include "SynTree/Type.h"              // for Type, Type::StorageClasses
 #include "SynTree/TypeSubstitution.h"  // for TypeSubstitution, operator<<
+#include "SynTree/DeclReplacer.h"      // for DeclReplacer
 #include "SynTree/Visitor.h"           // for acceptAll, maybeAccept
 
@@ -162 +163 @@
                         using Parent::previsit;
 
-                        void previsit( ObjectDecl * objDecl );
                         void previsit( FunctionDecl * funcDecl );
 
-                        void previsit( CompoundStmt * compoundStmt );
-                        void postvisit( CompoundStmt * compoundStmt );
-                        void previsit( ReturnStmt * returnStmt );
                         void previsit( BranchStmt * stmt );
                 private:
@@ -207 +204 @@
                         static void generate( std::list< Declaration * > & translationUnit );
 
+                        void premutate( StructDecl * structDecl );
+
                         void premutate( FunctionDecl * funcDecl );
                         DeclarationWithType * postmutate( FunctionDecl * funcDecl );
@@ -228 +227 @@
                         bool isCtor = false; // true if current function is a constructor
                         StructDecl * structDecl = nullptr;
+
+                        // special built-in functions necessary for this to work
+                        StructDecl * dtorStruct = nullptr;
+                        FunctionDecl * dtorStructDestroy = nullptr;
                 };
 
@@ -732 +735 @@
                 }
 
+                DeclarationWithType * getDtorFunc( ObjectDecl * objDecl, Statement * input, std::list< Statement * > & stmtsToAdd ) {
+                        // unwrap implicit statement wrapper
+                        Statement * dtor = input;
+                        if ( ImplicitCtorDtorStmt * implicit = dynamic_cast< ImplicitCtorDtorStmt * >( input ) ) {
+                                // dtor = implicit->callStmt;
+                                // implicit->callStmt = nullptr;
+                        }
+                        assert( dtor );
+                        std::list< Expression * > matches;
+                        collectCtorDtorCalls( dtor, matches );
+
+                        if ( dynamic_cast< ExprStmt * >( dtor ) ) {
+                                // only one destructor call in the expression
+                                if ( matches.size() == 1 ) {
+                                        DeclarationWithType * func = getFunction( matches.front() );
+                                        assertf( func, "getFunction failed to find function in %s", toString( matches.front() ).c_str() );
+
+                                        // cleanup argument must be a function, not an object (including function pointer)
+                                        if ( FunctionDecl * dtorFunc = dynamic_cast< FunctionDecl * > ( func ) ) {
+                                                if ( dtorFunc->type->forall.empty() ) {
+                                                        // simple case where the destructor is a monomorphic function call - can simply
+                                                        // use that function as the cleanup function.
+                                                        delete dtor;
+                                                        return func;
+                                                }
+                                        }
+                                }
+                        }
+
+                        // otherwise the cleanup is more complicated - need to build a single argument cleanup function that
+                        // wraps the more complicated code.
+                        static UniqueName dtorNamer( "__cleanup_dtor" );
+                        FunctionDecl * dtorFunc = FunctionDecl::newFunction( dtorNamer.newName(), SymTab::genDefaultType( objDecl->type->stripReferences(), false ), new CompoundStmt() );
+                        stmtsToAdd.push_back( new DeclStmt( dtorFunc ) );
+
+                        // the original code contains uses of objDecl - replace them with the newly generated 'this' parameter.
+                        ObjectDecl * thisParam = getParamThis( dtorFunc->type );
+                        Expression * replacement = new VariableExpr( thisParam );
+
+                        Type * base = replacement->result->stripReferences();
+                        if ( dynamic_cast< ArrayType * >( base ) || dynamic_cast< TupleType * > ( base ) ) {
+                                // need to cast away reference for array types, since the destructor is generated without the reference type,
+                                // and for tuple types since tuple indexing does not work directly on a reference
+                                replacement = new CastExpr( replacement, base->clone() );
+                        }
+                        DeclReplacer::replace( dtor, { std::make_pair( objDecl, replacement ) } );
+                        dtorFunc->statements->push_back( strict_dynamic_cast<Statement *>( dtor ) );
+
+                        return dtorFunc;
+                }
+
                 DeclarationWithType * FixInit::postmutate( ObjectDecl *objDecl ) {
                         // since this removes the init field from objDecl, it must occur after children are mutated (i.e. postmutate)
@@ -844 +898 @@
                                                         ctorInit->ctor = nullptr;
                                                 }
+
+                                                Statement * dtor = ctorInit->dtor;
+                                                if ( dtor ) {
+                                                        ImplicitCtorDtorStmt * implicit = strict_dynamic_cast< ImplicitCtorDtorStmt * >( dtor );
+                                                        Statement * dtorStmt = implicit->callStmt;
+
+                                                        // don't need to call intrinsic dtor, because it does nothing, but
+                                                        // non-intrinsic dtors must be called
+                                                        if ( ! isIntrinsicSingleArgCallStmt( dtorStmt ) ) {
+                                                                // set dtor location to the object's location for error messages
+                                                                DeclarationWithType * dtorFunc = getDtorFunc( objDecl, dtorStmt, stmtsToAddBefore );
+                                                                objDecl->attributes.push_back( new Attribute( "cleanup", { new VariableExpr( dtorFunc ) } ) );
+                                                                ctorInit->dtor = nullptr;
+                                                        } // if
+                                                }
                                         } // if
                                 } else if ( Initializer * init = ctorInit->init ) {
@@ -886 +955 @@
 
 
-                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();
-                        } // for
-                }
-
-                void InsertDtors::previsit( ObjectDecl * objDecl ) {
-                        // remember non-static destructed objects so that their destructors can be inserted later
-                        if ( ! objDecl->get_storageClasses().is_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();
-                                        // don't need to call intrinsic dtor, because it does nothing, but
-                                        // non-intrinsic dtors must be called
-                                        if ( dtor && ! isIntrinsicSingleArgCallStmt( dtor ) ) {
-                                                // set dtor location to the object's location for error messages
-                                                ctorInit->dtor->location = objDecl->location;
-                                                reverseDeclOrder.front().push_front( objDecl );
-                                        } // if
-                                } // if
-                        } // if
-                }
-
                 void InsertDtors::previsit( FunctionDecl * funcDecl ) {
                         // each function needs to have its own set of labels
@@ -930 +967 @@
                 }
 
-                void InsertDtors::previsit( 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::previsit( compoundStmt );
-                }
-
-                void InsertDtors::postvisit( CompoundStmt * compoundStmt ) {
-                        // add destructors for the current scope that we're exiting, unless the last statement is a return, which
-                        // causes unreachable code warnings
-                        std::list< Statement * > & statements = compoundStmt->get_kids();
-                        if ( ! statements.empty() && ! dynamic_cast< ReturnStmt * >( statements.back() ) ) {
-                                insertDtors( reverseDeclOrder.front().begin(), reverseDeclOrder.front().end(), back_inserter( statements ) );
-                        }
-                        reverseDeclOrder.pop_front();
-                }
-
-                void InsertDtors::previsit( ReturnStmt * ) {
-                        // return exits all scopes, so dump destructors for all scopes
-                        for ( OrderedDecls & od : reverseDeclOrder ) {
-                                insertDtors( od.begin(), od.end(), back_inserter( stmtsToAddBefore ) );
-                        } // for
-                }
-
                 // 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
@@ -982 +994 @@
                         if ( ! diff.empty() ) {
                                 SemanticError( stmt, std::string("jump to label '") + stmt->get_target().get_name() + "' crosses initialization of " + (*diff.begin())->get_name() + " " );
-                        } // if
-                        // 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() ) {
-                                // create an auxilliary set for fast lookup -- can't make diff a set, because diff ordering should be consistent for error messages.
-                                std::unordered_set<ObjectDecl *> needsDestructor( diff.begin(), diff.end() );
-
-                                // 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 needsDestructor.count( objDecl ); } );
-                                } // for
-                                insertDtors( ordered.begin(), ordered.end(), back_inserter( stmtsToAddBefore ) );
                         } // if
                 }
@@ -1025 +1019 @@
                 }
 
+                void GenStructMemberCalls::premutate( StructDecl * structDecl ) {
+                        if ( ! dtorStruct && structDecl->name == "__Destructor" ) {
+                                dtorStruct = structDecl;
+                        }
+                }
+
                 void GenStructMemberCalls::premutate( FunctionDecl * funcDecl ) {
                         GuardValue( function );
@@ -1037 +1037 @@
                         unhandled.clear();
                         usedUninit.clear();
+
+                        if ( ! dtorStructDestroy && funcDecl->name == "__destroy_Destructor" ) {
+                                dtorStructDestroy = funcDecl;
+                                return;
+                        }
 
                         function = funcDecl;
@@ -1048 +1053 @@
                                 if ( structType ) {
                                         structDecl = structType->get_baseStruct();
+                                        if ( structDecl == dtorStruct ) return;
                                         for ( Declaration * member : structDecl->get_members() ) {
                                                 if ( ObjectDecl * field = dynamic_cast< ObjectDecl * >( member ) ) {
@@ -1116 +1122 @@
                                                         callStmt->acceptMutator( *visitor );
                                                         if ( isCtor ) {
-                                                                function->get_statements()->push_front( callStmt );
+                                                                function->statements->push_front( callStmt );
                                                         } else {
                                                                 // destructor statements should be added at the end
-                                                                function->get_statements()->push_back( callStmt );
+                                                                // function->get_statements()->push_back( callStmt );
+
+                                                                // Destructor _dtor0 = { &b.a1, (void (*)(void *)_destroy_A };
+                                                                std::list< Statement * > stmtsToAdd;
+
+                                                                static UniqueName memberDtorNamer = { "__memberDtor" };
+                                                                assertf( dtorStruct, "builtin __Destructor not found." );
+                                                                assertf( dtorStructDestroy, "builtin __destroy_Destructor not found." );
+
+                                                                Expression * thisExpr = new AddressExpr( new VariableExpr( thisParam ) );
+                                                                Expression * dtorExpr = new VariableExpr( getDtorFunc( thisParam, callStmt, stmtsToAdd ) );
+
+                                                                // cast destructor pointer to void (*)(void *), to silence GCC incompatible pointer warnings
+                                                                FunctionType * dtorFtype = new FunctionType( Type::Qualifiers(), false );
+                                                                dtorFtype->parameters.push_back( ObjectDecl::newObject( "", new PointerType( Type::Qualifiers(), new VoidType( Type::Qualifiers() ) ), nullptr ) );
+                                                                Type * dtorType = new PointerType( Type::Qualifiers(), dtorFtype );
+
+                                                                ObjectDecl * destructor = ObjectDecl::newObject( memberDtorNamer.newName(), new StructInstType( Type::Qualifiers(), dtorStruct ), new ListInit( { new SingleInit( thisExpr ), new SingleInit( new CastExpr( dtorExpr, dtorType ) ) } ) );
+                                                                function->statements->push_front( new DeclStmt( destructor ) );
+                                                                destructor->attributes.push_back( new Attribute( "cleanup", { new VariableExpr( dtorStructDestroy ) } ) );
+
+                                                                function->statements->kids.splice( function->statements->kids.begin(), stmtsToAdd );
                                                         }
                                                 } catch ( SemanticErrorException & error ) {

src/InitTweak/InitTweak.cc

@@ -339 +339 @@
                 std::list< Expression * > matches;
                 collectCtorDtorCalls( stmt, matches );
-                assert( matches.size() <= 1 );
+                assertf( matches.size() <= 1, "%zd constructor/destructors found in %s", matches.size(), toString( stmt ).c_str() );
                 return matches.size() == 1 ? matches.front() : nullptr;
         }

src/SymTab/Autogen.cc

@@ -45 +45 @@
         /// Data used to generate functions generically. Specifically, the name of the generated function and a function which generates the routine protoype
         struct FuncData {
-                typedef FunctionType * (*TypeGen)( Type * );
+                typedef FunctionType * (*TypeGen)( Type *, bool );
                 FuncData( const std::string & fname, const TypeGen & genType ) : fname( fname ), genType( genType ) {}
                 std::string fname;
@@ -231 +231 @@
 
         /// given type T, generate type of default ctor/dtor, i.e. function type void (*) (T *)
-        FunctionType * genDefaultType( Type * paramType ) {
-                const auto & typeParams = getGenericParams( paramType );
+        FunctionType * genDefaultType( Type * paramType, bool maybePolymorphic ) {
                 FunctionType *ftype = new FunctionType( Type::Qualifiers(), false );
-                cloneAll( typeParams, ftype->forall );
+                if ( maybePolymorphic ) {
+                        // only copy in
+                        const auto & typeParams = getGenericParams( paramType );
+                        cloneAll( typeParams, ftype->forall );
+                }
                 ObjectDecl *dstParam = new ObjectDecl( "_dst", Type::StorageClasses(), LinkageSpec::Cforall, nullptr, new ReferenceType( Type::Qualifiers(), paramType->clone() ), nullptr );
                 ftype->parameters.push_back( dstParam );
@@ -241 +244 @@
 
         /// given type T, generate type of copy ctor, i.e. function type void (*) (T *, T)
-        FunctionType * genCopyType( Type * paramType ) {
-                FunctionType *ftype = genDefaultType( paramType );
+        FunctionType * genCopyType( Type * paramType, bool maybePolymorphic ) {
+                FunctionType *ftype = genDefaultType( paramType, maybePolymorphic );
                 ObjectDecl *srcParam = new ObjectDecl( "_src", Type::StorageClasses(), LinkageSpec::Cforall, nullptr, paramType->clone(), nullptr );
                 ftype->parameters.push_back( srcParam );
@@ -249 +252 @@
 
         /// given type T, generate type of assignment, i.e. function type T (*) (T *, T)
-        FunctionType * genAssignType( Type * paramType ) {
-                FunctionType *ftype = genCopyType( paramType );
+        FunctionType * genAssignType( Type * paramType, bool maybePolymorphic ) {
+                FunctionType *ftype = genCopyType( paramType, maybePolymorphic );
                 ObjectDecl *returnVal = new ObjectDecl( "_ret", Type::StorageClasses(), LinkageSpec::Cforall, nullptr, paramType->clone(), nullptr );
                 ftype->returnVals.push_back( returnVal );
@@ -308 +311 @@
                 for ( const FuncData & d : data ) {
                         // generate a function (?{}, ?=?, ^?{}) based on the current FuncData.
-                        FunctionType * ftype = d.genType( type );
+                        FunctionType * ftype = d.genType( type, true );
 
                         // destructor for concurrent type must be mutex

src/SymTab/Autogen.h

@@ -45 +45 @@
         extern FunctionDecl * dereferenceOperator;
 
-        // generate the type of an assignment function for paramType
-        FunctionType * genAssignType( Type * paramType );
-
-        // generate the type of a default constructor or destructor for paramType
-        FunctionType * genDefaultType( Type * paramType );
-
-        // generate the type of a copy constructor for paramType
-        FunctionType * genCopyType( Type * paramType );
+        /// generate the type of an assignment function for paramType.
+        /// maybePolymorphic is true if the resulting FunctionType is allowed to be polymorphic
+        FunctionType * genAssignType( Type * paramType, bool maybePolymorphic = true );
+
+        /// generate the type of a default constructor or destructor for paramType.
+        /// maybePolymorphic is true if the resulting FunctionType is allowed to be polymorphic
+        FunctionType * genDefaultType( Type * paramType, bool maybePolymorphic = true );
+
+        /// generate the type of a copy constructor for paramType.
+        /// maybePolymorphic is true if the resulting FunctionType is allowed to be polymorphic
+        FunctionType * genCopyType( Type * paramType, bool maybePolymorphic = true );
 
         /// inserts into out a generated call expression to function fname with arguments dstParam and srcParam. Intended to be used with generated ?=?, ?{}, and ^?{} calls.

src/SynTree/DeclReplacer.cc

@@ -38 +38 @@
                         void previsit( TypeInstType * inst );
                 };
+
+                /// Mutator that replaces uses of declarations with arbitrary expressions, according to the supplied mapping
+                struct ExprDeclReplacer {
+                private:
+                        const ExprMap & exprMap;
+                        bool debug;
+                public:
+                        ExprDeclReplacer( const ExprMap & exprMap, bool debug = false );
+
+                        // replace variable with new node from expr map
+                        Expression * postmutate( VariableExpr * varExpr );
+                };
         }
 
@@ -53 +65 @@
                 DeclMap declMap;
                 replace( node, declMap, typeMap, debug );
+        }
+
+        void replace( BaseSyntaxNode *& node, const ExprMap & exprMap, bool debug ) {
+                PassVisitor<ExprDeclReplacer> replacer( exprMap, debug );
+                node = maybeMutate( node, replacer );
         }
 
@@ -79 +96 @@
                         }
                 }
+
+                ExprDeclReplacer::ExprDeclReplacer( const ExprMap & exprMap, bool debug ) : exprMap( exprMap ), debug( debug ) {}
+
+                Expression * ExprDeclReplacer::postmutate( VariableExpr * varExpr ) {
+                        if ( exprMap.count( varExpr->var ) ) {
+                                Expression * replacement = exprMap.at( varExpr->var )->clone();
+                                if ( debug ) {
+                                        std::cerr << "replacing variable reference: " << (void*)varExpr->var << " " << varExpr->var << " with " << (void*)replacement << " " << replacement << std::endl;
+                                }
+                                std::swap( varExpr->env, replacement->env );
+                                delete varExpr;
+                                return replacement;
+                        }
+                        return varExpr;
+                }
         }
 } // namespace VarExprReplacer

src/SynTree/DeclReplacer.h

@@ -26 +26 @@
         typedef std::map< DeclarationWithType *, DeclarationWithType * > DeclMap;
         typedef std::map< TypeDecl *, TypeDecl * > TypeMap;
+        typedef std::map< DeclarationWithType *, Expression * > ExprMap;
 
         void replace( BaseSyntaxNode * node, const DeclMap & declMap, bool debug = false );
         void replace( BaseSyntaxNode * node, const TypeMap & typeMap, bool debug = false );
         void replace( BaseSyntaxNode * node, const DeclMap & declMap, const TypeMap & typeMap, bool debug = false );
+
+        void replace( BaseSyntaxNode *& node, const ExprMap & exprMap, bool debug = false);
+        template<typename T>
+                void replace( T *& node, const ExprMap & exprMap, bool debug = false ) {
+                if ( ! node ) return;
+                BaseSyntaxNode * arg = node;
+                replace( arg, exprMap, debug );
+                node = dynamic_cast<T *>( arg );
+                assertf( node, "DeclReplacer fundamentally changed the type of its argument." );
+        }
 }
 

tests/raii/.expect/memberCtors.txt

@@ -98 +98 @@
 end copy construct A
 End of main
+begin destruct B
 constructing int
 constructing int
@@ -146 +147 @@
 destructing int: 0
 destructing int: 1000
-destructing int: 0
-destructing int: 0
-destructing int: 999
-destructing int: 0
-destructing int: 0
-destructing int: 0
-destructing int: 0
-destructing int: 0
-destructing int: 999
+end destruct B
+destructing int: 0
+destructing int: 0
+destructing int: 999
+destructing int: 0
+destructing int: 0
+destructing int: 0
+destructing int: 0
+destructing int: 0
+destructing int: 999
+begin destruct B
 constructing int
 constructing int
@@ -203 +206 @@
 destructing int: 0
 destructing int: 1000
-destructing int: 0
-destructing int: 0
-destructing int: 999
-destructing int: 0
-destructing int: 0
-destructing int: 0
-destructing int: 0
-destructing int: 0
-destructing int: 999
+end destruct B
+destructing int: 0
+destructing int: 0
+destructing int: 999
+destructing int: 0
+destructing int: 0
+destructing int: 0
+destructing int: 0
+destructing int: 0
+destructing int: 999

tests/raii/memberCtors.c

@@ -22 +22 @@
 }
 
-void ?=?(WrappedInt & this, int x) {
+/* WrappedInt */ void ?=?(WrappedInt & this, int x) {
   printf("assigning int: %d %d\n", this.x, x);
   this.x = x;
+  // return this;
 }
+
+// WrappedInt ?=?(WrappedInt & this, WrappedInt other) {
+//   printf("assigning int: %d %d\n", this.x, other.x);
+//   this.x = other.x;
+//   return this;
+// }
 
 struct A {
@@ -79 +86 @@
 
 void ^?{}(B & b) {
+  printf("begin destruct B\n");
   b.a2 = (A) { 0 };
   ^(b.a1){};
+  printf("end destruct B\n");
 } // a2, a3 never destructed - will be automatically destructed
 
 int main() {
   printf("Before declaration of b1\n");
-  B b1;
+  B b1;  // b1 = { { 1000, 0, 0 }, { 1001, 0, 0 }, { 0, 0, 0 } }
   printf("Before declaration of b2\n");
   B b2 = b1;