Memory leaks 为什么此接口委派会导致内存泄漏?
假设我有以下代码 单位TalkerIntf.pasMemory leaks 为什么此接口委派会导致内存泄漏?,memory-leaks,freepascal,Memory Leaks,Freepascal,假设我有以下代码 单位TalkerIntf.pas unit TalkerIntf; interface {$MODE OBJFPC} type ITalker = interface ['{95E1FAE3-7495-4404-AE88-6A7DB88383EC}'] procedure say() ; end; implementation end. unit TalkerImpl; interface {$MODE OBJFP
unit TalkerIntf;
interface
{$MODE OBJFPC}
type
ITalker = interface
['{95E1FAE3-7495-4404-AE88-6A7DB88383EC}']
procedure say() ;
end;
implementation
end.
unit TalkerImpl;
interface
{$MODE OBJFPC}
uses
TalkerIntf;
type
TTalker = class(TInterfacedObject, ITalker)
public
procedure say();
end;
implementation
procedure TTalker.say();
begin
writeln('Hello');
end;
end.
unit DelegateTalkerImpl;
interface
{$MODE OBJFPC}
uses
TalkerIntf;
type
TDelegateTalker = class(TInterfacedObject, ITalker)
private
fActualTalker : ITalker;
public
constructor create(const talker : ITalker);
destructor destroy(); override;
property talker : ITalker read fActualTalker implements ITalker;
end;
implementation
constructor TDelegateTalker.create(const talker : ITalker);
begin
fActualTalker := talker;
end;
destructor TDelegateTalker.destroy();
begin
fActualTalker := nil;
inherited destroy();
end;
end.
program memleak;
{$MODE OBJFPC}
uses
TalkerIntf,
TalkerImpl,
DelegateTalkerImpl;
var
talker : ITalker;
begin
talker := TDelegateTalker.create(TTalker.create());
talker.say();
end.
单位TalkerImpl.pas
unit TalkerIntf;
interface
{$MODE OBJFPC}
type
ITalker = interface
['{95E1FAE3-7495-4404-AE88-6A7DB88383EC}']
procedure say() ;
end;
implementation
end.
unit TalkerImpl;
interface
{$MODE OBJFPC}
uses
TalkerIntf;
type
TTalker = class(TInterfacedObject, ITalker)
public
procedure say();
end;
implementation
procedure TTalker.say();
begin
writeln('Hello');
end;
end.
unit DelegateTalkerImpl;
interface
{$MODE OBJFPC}
uses
TalkerIntf;
type
TDelegateTalker = class(TInterfacedObject, ITalker)
private
fActualTalker : ITalker;
public
constructor create(const talker : ITalker);
destructor destroy(); override;
property talker : ITalker read fActualTalker implements ITalker;
end;
implementation
constructor TDelegateTalker.create(const talker : ITalker);
begin
fActualTalker := talker;
end;
destructor TDelegateTalker.destroy();
begin
fActualTalker := nil;
inherited destroy();
end;
end.
program memleak;
{$MODE OBJFPC}
uses
TalkerIntf,
TalkerImpl,
DelegateTalkerImpl;
var
talker : ITalker;
begin
talker := TDelegateTalker.create(TTalker.create());
talker.say();
end.
单位DelegateTalkerImpl.pas
unit TalkerIntf;
interface
{$MODE OBJFPC}
type
ITalker = interface
['{95E1FAE3-7495-4404-AE88-6A7DB88383EC}']
procedure say() ;
end;
implementation
end.
unit TalkerImpl;
interface
{$MODE OBJFPC}
uses
TalkerIntf;
type
TTalker = class(TInterfacedObject, ITalker)
public
procedure say();
end;
implementation
procedure TTalker.say();
begin
writeln('Hello');
end;
end.
unit DelegateTalkerImpl;
interface
{$MODE OBJFPC}
uses
TalkerIntf;
type
TDelegateTalker = class(TInterfacedObject, ITalker)
private
fActualTalker : ITalker;
public
constructor create(const talker : ITalker);
destructor destroy(); override;
property talker : ITalker read fActualTalker implements ITalker;
end;
implementation
constructor TDelegateTalker.create(const talker : ITalker);
begin
fActualTalker := talker;
end;
destructor TDelegateTalker.destroy();
begin
fActualTalker := nil;
inherited destroy();
end;
end.
program memleak;
{$MODE OBJFPC}
uses
TalkerIntf,
TalkerImpl,
DelegateTalkerImpl;
var
talker : ITalker;
begin
talker := TDelegateTalker.create(TTalker.create());
talker.say();
end.
和程序memleak.pas
unit TalkerIntf;
interface
{$MODE OBJFPC}
type
ITalker = interface
['{95E1FAE3-7495-4404-AE88-6A7DB88383EC}']
procedure say() ;
end;
implementation
end.
unit TalkerImpl;
interface
{$MODE OBJFPC}
uses
TalkerIntf;
type
TTalker = class(TInterfacedObject, ITalker)
public
procedure say();
end;
implementation
procedure TTalker.say();
begin
writeln('Hello');
end;
end.
unit DelegateTalkerImpl;
interface
{$MODE OBJFPC}
uses
TalkerIntf;
type
TDelegateTalker = class(TInterfacedObject, ITalker)
private
fActualTalker : ITalker;
public
constructor create(const talker : ITalker);
destructor destroy(); override;
property talker : ITalker read fActualTalker implements ITalker;
end;
implementation
constructor TDelegateTalker.create(const talker : ITalker);
begin
fActualTalker := talker;
end;
destructor TDelegateTalker.destroy();
begin
fActualTalker := nil;
inherited destroy();
end;
end.
program memleak;
{$MODE OBJFPC}
uses
TalkerIntf,
TalkerImpl,
DelegateTalkerImpl;
var
talker : ITalker;
begin
talker := TDelegateTalker.create(TTalker.create());
talker.say();
end.
使用FreePascal 3.0.4和heaptrc on(-gh
)编译时,heaptrc报告存在内存泄漏
$ fpc -gh memleak.pas
$ ./memleak
Heaptrc输出
Hello
Heap dump by heaptrc unit
2 memory blocks allocated : 64/64
0 memory blocks freed : 0/0
2 unfreed memory blocks : 64
True heap size : 32768
True free heap : 32384
Should be : 32448
Call trace for block $00007FA0D7846180 size 32
$000000000040020F
Call trace for block $00007FA0D78460C0 size 32
为什么此接口委派会导致内存泄漏?如何避免呢
更新
似乎唯一的解决办法是删除实现并手动执行委派。以下代码没有内存泄漏
unit DelegateTalkerImpl;
interface
{$MODE OBJFPC}
uses
TalkerIntf;
type
TDelegateTalker = class(TInterfacedObject, ITalker)
private
fActualTalker : ITalker;
public
constructor create(const talker : ITalker);
destructor destroy(); override;
procedure say();
end;
implementation
constructor TDelegateTalker.create(const talker : ITalker);
begin
fActualTalker := talker;
end;
destructor TDelegateTalker.destroy();
begin
fActualTalker := nil;
inherited destroy();
end;
procedure TDelegateTalker.say();
begin
fActualTalker.say();
end;
end.
据
将变量定义为ITalker时,不会返回新创建的对象,而只返回实现它的字段。结果,新创建的对象被泄漏。
德尔福的行为也是如此
为了避免内存泄漏,但仍然使用implements
关键字,我们需要将其分配给类型不是ITalker
的临时变量,然后将其键入ITalker
var
talker : ITalker;
delegateTalker : IInterface;
begin
delegateTalker := TDelegateTalker.create(TTalker.create());
talker := delegateTalker as ITalker;
talker.say();
end.
我认为这是fpc复制一个长期存在的Delphi错误的案例,它似乎永远不会被修复。