从C#COM dll回调到Delphi应用程序导致内存泄漏
我有一个用C#编写的COM服务器和一个用Delphi编写的COM客户端。我已经实现了一个简单而优雅的回调机制,它的工作方式很有魅力。但是,FastMM4报告我的Delphi客户端正在创建内存泄漏。我已将应用程序提炼为泄漏的根源。我知道泄漏是由对象被引用计数的方式造成的(它从不归零,所以也不会被破坏),所以我试图理解为什么引用计数是这样工作的,是因为我在实现中做了一些错误的事情 我已经尽可能地减少了代码,但在一个问题中似乎仍然需要包含很多内容。但我真的不知道如何解释我在做什么。我把这两个项目(C#和Delphi)整齐地打包在一个zip文件中,但似乎我无法将其附加到任何地方 我在C端声明了两个接口(从C#COM dll回调到Delphi应用程序导致内存泄漏,c#,delphi,memory-leaks,com,idispatch,C#,Delphi,Memory Leaks,Com,Idispatch,我有一个用C#编写的COM服务器和一个用Delphi编写的COM客户端。我已经实现了一个简单而优雅的回调机制,它的工作方式很有魅力。但是,FastMM4报告我的Delphi客户端正在创建内存泄漏。我已将应用程序提炼为泄漏的根源。我知道泄漏是由对象被引用计数的方式造成的(它从不归零,所以也不会被破坏),所以我试图理解为什么引用计数是这样工作的,是因为我在实现中做了一些错误的事情 我已经尽可能地减少了代码,但在一个问题中似乎仍然需要包含很多内容。但我真的不知道如何解释我在做什么。我把这两个项目(C#
ICOMCallbackContainer
和ICOMCallbackTestServer
),并在那里实现了其中一个接口(COMCallbackTestServer
)。我正在Delphi端实现另一个接口(TCOMCallbackContainer
),并将Delphi类传递给C#类
这是C#COM服务器:
namespace COMCallbackTest
{
[ComVisible(true)]
[Guid("2AB7E954-0AAF-4CFE-844C-756E50FE6360")]
public interface ICOMCallbackContainer
{
void Callback(string message);
}
[ComVisible(true)]
[Guid("7717D7AE-B763-48BC-BA0B-0F3525BEE8A4")]
public interface ICOMCallbackTestServer
{
ICOMCallbackContainer CallbackContainer { get; set; }
void RunCOMProcess();
void Dispose();
}
[ComVisible(true)]
[Guid("CF33E3A7-0886-4A0D-A740-537D0640C641")]
public class COMCallbackTestServer : ICOMCallbackTestServer
{
ICOMCallbackContainer _callbackContainer;
ICOMCallbackContainer ICOMCallbackTestServer.CallbackContainer
{
get { return _callbackContainer; }
set { _callbackContainer = value; }
}
void ICOMCallbackTestServer.RunCOMProcess()
{
if (_callbackContainer != null)
{
_callbackContainer.Callback("Step One");
_callbackContainer.Callback("Step Two");
_callbackContainer.Callback("Step Three");
}
}
void ICOMCallbackTestServer.Dispose()
{
if (_callbackContainer != null)
_callbackContainer.Callback("Done");
}
}
}
这是Delphi回调容器:
type
TCOMCallbackMethod = reference to procedure(AMessage: string);
TCOMCallbackContainer = class(TAutoIntfObject, ICOMCallbackContainer)
private
FCallbackMethod: TCOMCallbackMethod;
procedure Callback(const message: WideString); safecall;
public
constructor Create(ACallbackMethod: TCOMCallbackMethod);
destructor Destroy; override;
end;
// ...
constructor TCOMCallbackContainer.Create(ACallbackMethod: TCOMCallbackMethod);
var
typeLib: ITypeLib;
begin
OleCheck(LoadRegTypeLib(LIBID_COMCallbackTestServer,
COMCallbackTestServerMajorVersion,
COMCallbackTestServerMinorVersion,
0,
{out} typeLib));
inherited Create(typeLib, ICOMCallbackContainer);
FCallbackMethod := ACallbackMethod;
end;
destructor TCOMCallbackContainer.Destroy;
begin
FCallbackMethod := nil;
inherited Destroy;
end;
procedure TCOMCallbackContainer.Callback(const message: WideString);
begin
if Assigned(FCallbackMethod) then
FCallbackMethod(message);
end;
...
CLR -> TInterfacedObject._AddRef: 2
CLR -> TInterfacedObject.QueryInterface(INoMarshal): S_OK
CLR -> TInterfacedObject.QueryInterface -> TObject.GetInterface -> _AddRef: 3
CLR -> TInterfacedObject._Release: 2
CLR -> TInterfacedObject.QueryInterface(IRpcOptions): E_NOINTERFACE
CLR -> TInterfacedObject._Release: 1
...
...
CLR -> TInterfacedObject._AddRef: 2
CLR -> TInterfacedObject.QueryInterface(INoMarshal): E_NOINTERFACE
CLR -> TInterfacedObject.QueryInterface(IAgileObject): S_OK
CLR -> TInterfacedObject.QueryInterface -> TObject.GetInterface -> _AddRef: 3
CLR -> TInterfacedObject._Release: 2
CLR -> TInterfacedObject.QueryInterface(IRpcOptions): E_NOINTERFACE
CLR -> TInterfacedObject._Release: 1
...
TCOMCallbackContainer继承自TAutoIntfObject,因此它实现IDispatch。我不知道我在构造函数中做的事情是否正确。我不太熟悉如何使用IDispatch
这是Delphi COM客户端:
procedure TfrmMain.FormCreate(Sender: TObject);
begin
FServer := CoCOMCallbackTestServer_.Create as ICOMCallbackTestServer;
// Increments RefCount by 2, expected 1
FServer.CallbackContainer := TCOMCallbackContainer.Create(Process_Callback);
end;
procedure TfrmMain.FormDestroy(Sender: TObject);
begin
// Decrements RefCount by 0, expected 1
FServer.CallbackContainer := nil;
FServer.Dispose;
FServer := nil;
end;
procedure TfrmMain.btnBeginProcessClick(Sender: TObject);
begin
FServer.RunCOMProcess;
end;
procedure TfrmMain.Process_Callback(AMessage: string);
begin
mmoProcessMessages.Lines.Add(AMessage);
end;
上面的TCOMCallbackContainer实例永远不会被销毁,因为RefCount永远不会低于2
所以我的问题是,为什么将回调容器对象分配给COM属性会使引用计数增加两倍,而将nil分配给COM属性则根本不会减少引用计数
编辑
我创建了TMyInterfacedObject(与TInterfacedObject相同),并将其用作TCOMCallbackContainer的基类。我在TMyInterfacedObject的每个方法中放置断点。在每个断点,我都记录了调用堆栈(以及一些其他信息)。对于更新RefCount的每个方法,行末尾的数字将显示RefCount的新值。对于QueryInterface,我包括了IID和相应的接口名(通过Google找到)以及调用的结果
TfrmMain.FormCreate -> TCOMCallbackContainer.Create -> TInterfacedObject.NewInstance: 1
TfrmMain.FormCreate -> TCOMCallbackContainer.Create -> TInterfacedObject.AfterConstruction: 0
CLR -> TInterfacedObject.QueryInterface("00000000-0000-0000-C000-000000000046" {IUnknown}): S_OK
CLR -> TInterfacedObject.QueryInterface -> TObject.GetInterface -> _AddRef: 1
CLR -> TInterfacedObject.QueryInterface("C3FCC19E-A970-11D2-8B5A-00A0C9B7C9C4" {IManagedObject}): E_NOINTERFACE
CLR -> TInterfacedObject.QueryInterface("B196B283-BAB4-101A-B69C-00AA00341D07" {IProvideClassInfo}): E_NOINTERFACE
CLR -> TInterfacedObject._AddRef: 2
CLR -> TInterfacedObject.QueryInterface("ECC8691B-C1DB-4DC0-855E-65F6C551AF49" {INoMarshal}): E_NOINTERFACE
CLR -> TInterfacedObject.QueryInterface("94EA2B94-E9CC-49E0-C0FF-EE64CA8F5B90" {IAgileObject}): E_NOINTERFACE
CLR -> TInterfacedObject.QueryInterface("00000003-0000-0000-C000-000000000046" {IMarshal}): E_NOINTERFACE
CLR -> TInterfacedObject.QueryInterface("00000144-0000-0000-C000-000000000046" {IRpcOptions}): E_NOINTERFACE
CLR -> TInterfacedObject._Release: 1
CLR -> TInterfacedObject.QueryInterface("2AB7E954-0AAF-4CFE-844C-756E50FE6360" {ICOMCallbackContainer}): S_OK
CLR -> TInterfacedObject.QueryInterface -> TObject.GetInterface -> _AddRef: 2
CLR -> TInterfacedObject._AddRef: 3
CLR -> TInterfacedObject._Release: 2
列出的所有断点都发生在FServer.CallbackContainer:=TCOMCallbackContainer.Create(Process\u Callback)中语句。在Destroy方法中,尤其是在FServer.CallbackContainer:=nil代码>语句,未命中任何断点
我想,也许是COM库在调用析构函数之前被卸载了,所以我复制了FServer.CallbackContainer:=nil代码>行到构造函数的末尾。这没什么区别
传递给QueryInterface调用的接口在Delphi环境中似乎不可用,因此我将尝试将其中一些接口继承到C#端的ICOMCallbackContainer中,以使它们可用(在研究它们应该做什么以及如何工作之后)
编辑2
我尝试实现INoMarshal和IAgileObject只是为了看看会发生什么。我尝试了这两种方法,因为它们都是标记接口,实际上没有什么可实现的。它稍微改变了这个过程,但没有任何帮助。看起来,如果CLR找到了INoMarshal,那么它不会查找IAgileObject或IMarshal;如果它没有找到INoMarshal,但是找到了IAgileObject,那么它不会查找IMarshal。(这似乎并不重要,甚至对我来说也没有意义。)
将INoMarshal添加到TCOMCallbackContainer后:
type
TCOMCallbackMethod = reference to procedure(AMessage: string);
TCOMCallbackContainer = class(TAutoIntfObject, ICOMCallbackContainer)
private
FCallbackMethod: TCOMCallbackMethod;
procedure Callback(const message: WideString); safecall;
public
constructor Create(ACallbackMethod: TCOMCallbackMethod);
destructor Destroy; override;
end;
// ...
constructor TCOMCallbackContainer.Create(ACallbackMethod: TCOMCallbackMethod);
var
typeLib: ITypeLib;
begin
OleCheck(LoadRegTypeLib(LIBID_COMCallbackTestServer,
COMCallbackTestServerMajorVersion,
COMCallbackTestServerMinorVersion,
0,
{out} typeLib));
inherited Create(typeLib, ICOMCallbackContainer);
FCallbackMethod := ACallbackMethod;
end;
destructor TCOMCallbackContainer.Destroy;
begin
FCallbackMethod := nil;
inherited Destroy;
end;
procedure TCOMCallbackContainer.Callback(const message: WideString);
begin
if Assigned(FCallbackMethod) then
FCallbackMethod(message);
end;
...
CLR -> TInterfacedObject._AddRef: 2
CLR -> TInterfacedObject.QueryInterface(INoMarshal): S_OK
CLR -> TInterfacedObject.QueryInterface -> TObject.GetInterface -> _AddRef: 3
CLR -> TInterfacedObject._Release: 2
CLR -> TInterfacedObject.QueryInterface(IRpcOptions): E_NOINTERFACE
CLR -> TInterfacedObject._Release: 1
...
...
CLR -> TInterfacedObject._AddRef: 2
CLR -> TInterfacedObject.QueryInterface(INoMarshal): E_NOINTERFACE
CLR -> TInterfacedObject.QueryInterface(IAgileObject): S_OK
CLR -> TInterfacedObject.QueryInterface -> TObject.GetInterface -> _AddRef: 3
CLR -> TInterfacedObject._Release: 2
CLR -> TInterfacedObject.QueryInterface(IRpcOptions): E_NOINTERFACE
CLR -> TInterfacedObject._Release: 1
...
将IAgileObject添加到TCOMCallbackContainer后:
type
TCOMCallbackMethod = reference to procedure(AMessage: string);
TCOMCallbackContainer = class(TAutoIntfObject, ICOMCallbackContainer)
private
FCallbackMethod: TCOMCallbackMethod;
procedure Callback(const message: WideString); safecall;
public
constructor Create(ACallbackMethod: TCOMCallbackMethod);
destructor Destroy; override;
end;
// ...
constructor TCOMCallbackContainer.Create(ACallbackMethod: TCOMCallbackMethod);
var
typeLib: ITypeLib;
begin
OleCheck(LoadRegTypeLib(LIBID_COMCallbackTestServer,
COMCallbackTestServerMajorVersion,
COMCallbackTestServerMinorVersion,
0,
{out} typeLib));
inherited Create(typeLib, ICOMCallbackContainer);
FCallbackMethod := ACallbackMethod;
end;
destructor TCOMCallbackContainer.Destroy;
begin
FCallbackMethod := nil;
inherited Destroy;
end;
procedure TCOMCallbackContainer.Callback(const message: WideString);
begin
if Assigned(FCallbackMethod) then
FCallbackMethod(message);
end;
...
CLR -> TInterfacedObject._AddRef: 2
CLR -> TInterfacedObject.QueryInterface(INoMarshal): S_OK
CLR -> TInterfacedObject.QueryInterface -> TObject.GetInterface -> _AddRef: 3
CLR -> TInterfacedObject._Release: 2
CLR -> TInterfacedObject.QueryInterface(IRpcOptions): E_NOINTERFACE
CLR -> TInterfacedObject._Release: 1
...
...
CLR -> TInterfacedObject._AddRef: 2
CLR -> TInterfacedObject.QueryInterface(INoMarshal): E_NOINTERFACE
CLR -> TInterfacedObject.QueryInterface(IAgileObject): S_OK
CLR -> TInterfacedObject.QueryInterface -> TObject.GetInterface -> _AddRef: 3
CLR -> TInterfacedObject._Release: 2
CLR -> TInterfacedObject.QueryInterface(IRpcOptions): E_NOINTERFACE
CLR -> TInterfacedObject._Release: 1
...
在托管代码中,外部COM接口被包装到(RCW)中。与原始COM接口不同,RCW的寿命由不使用引用计数的垃圾收集器确定。在您的特定情况下,这意味着对null的赋值不会立即减少refCount
可以通过显式调用强制COM对象引用释放:
[ComVisible(true)]
是否意味着字符串
被封送为BStr
?TCOMCallbackContainer。销毁
是毫无意义的。把它拿走。您的TAutoIntfObject
子分类在形式上与VCL中唯一的子分类相同,即TStringsAdapter
。所以我认为TCOMCallbackContainer
很好。COM服务器是如何导入的?这看起来合理吗。这是我们看不到的自动生成的代码。因此,cococomcallbacktestserver
类型和朋友。@DavidHeffernan,字符串类型在_TLB.pas文件中显示为WideString,我相信它与BStr相同。是的,WideString
和BStr
是兼容的。我更熟悉p/invoke,但是[ComVisible(true)]
暗示字符串BStr
显然是有意义的。在类中使用未解释的引用实现自己的AddRef和Release。在每个方法中添加断点,并在触发断点时查看调用堆栈。这至少可以确定推荐人的身份。非常感谢。这不仅修复了我所经历的泄漏,而且我也学到了一些东西。我肯定需要学习更多关于编组的知识。