C# - Marshal.GetIUnknownForObject/GetIDispatchForObject 사용 시 메모리 누수(Memory Leak) 발생
지난 글에서,
C# - GetNativeVariantForObject 사용 시 메모리 누수(Memory Leak) 발생 및 해결 방법
; https://www.sysnet.pe.kr/2/0/12157
발생한 메모리 누수와 유사한 현상이 GetIUnknownForObject과 GetIDispatchForObject에서도 나타납니다.
static unsafe void Main(string[] args)
{
int i = 0;
while (true)
{
TestHandleWithoutLeak();
i++;
if (i > 1000)
{
GC.Collect();
GC.Collect();
i = 0;
}
}
}
private unsafe static void TestHandleWithLeak()
{
object obj = new object();
{
IntPtr pointer = Marshal.GetIUnknownForObject(obj);
while (Marshal.Release(pointer) > 0) { };
}
}
위의 프로그램을 실행하면 메모리 누수가 발생하는데 "!gchandles"의 "Ref Count Handles"가 늘어나는 현상도 동일합니다. 실제로 검색해 보니 다음과 같은 글이 있군요. ^^;
IC65849: MEMORY LEAK FROM .NET PROVIDER METHOD IBM.DATA.INFORMIX.DBCWRAPPER.ENLISTASREQUIRED
; https://www-01.ibm.com/support/docview.wss?uid=swg1IC65849
The memory leak is caused by the IntPtr returned from Marshal.GetIUnknownForObject but never released with Marshal.Release().
문제는, 해당 메서드들이 반환하는 값은 이미 IUnknown/IDispatch 인터페이스의 포인터이기 때문에 VariantClear와 같은 해결책을 적용할 수 없다는 점입니다. 딱히 그 외에는 해볼 만한 것이 없어 저도 매끄러운 방법을 찾아내지는 못했습니다. (혹시 아시는 분은 덧글 부탁드립니다.)
단지, 우회하는 방법은 있는데 어차피 IUnknown이나 IDispatch는 Variant로부터도 구할 수 있으므로 다음과 같은 식으로 GetNativeVariantForObject를 감싸는 helper 클래스를 만들어,
public sealed class ObjectInterface : IDisposable
{
[DllImport("oleaut32.dll", PreserveSig = true)]
private static extern int VariantClear(IntPtr pObject);
unsafe static int _varSize = sizeof(Variant);
IntPtr _pAlloc;
unsafe Variant* _pVariant;
public void Dispose()
{
if (_pAlloc != IntPtr.Zero)
{
VariantClear(_pAlloc);
Marshal.FreeHGlobal(_pAlloc);
}
}
public unsafe ObjectInterface(object obj)
{
_pAlloc = Marshal.AllocHGlobal(_varSize);
Marshal.GetNativeVariantForObject(obj, _pAlloc);
_pVariant = (Variant *)_pAlloc.ToPointer();
}
public unsafe IntPtr Unknown
{
get
{
if (_pVariant == null)
{
return IntPtr.Zero;
}
if (_pVariant->vt != (ushort)VarEnum.VT_UNKNOWN && _pVariant->vt != (ushort)VarEnum.VT_DISPATCH)
{
return IntPtr.Zero;
}
return _pVariant->data01;
}
}
public unsafe IntPtr Dispatch
{
get
{
if (_pVariant == null)
{
return IntPtr.Zero;
}
if (_pVariant->vt != (ushort)VarEnum.VT_DISPATCH)
{
return IntPtr.Zero;
}
return _pVariant->data01;
}
}
[StructLayout(LayoutKind.Sequential)]
struct Variant
{
public ushort vt;
public ushort wReserved1;
public ushort wReserved2;
public ushort wReserved3;
public IntPtr data01;
public IntPtr data02;
}
}
이렇게 사용할 수 있습니다.
private unsafe static void TestHandleWithoutLeak()
{
object obj = new object();
{
// IntPtr pointer = Marshal.GetIUnknownForObject(obj); // memory-leak
// IntPtr pointer = Marshal.GetIDispatchForObject(obj); // memory-leak
using (ObjectInterface oi = new ObjectInterface(obj)) // NO memory-leak
{
IntPtr ptr = oi.Unknown;
// ptr = oi.Dispatch;
}
}
}
(
첨부 파일은 이 글의 예제 코드를 포함합니다.)
참고로, 아래의 코드는 Marshal.GetIUnknownForObject 함수이고,
clr!MarshalNative::GetIUnknownForObjectNative:
00007ffc`dc56bb60 488bc4 mov rax,rsp
00007ffc`dc56bb63 885010 mov byte ptr [rax+10h],dl
00007ffc`dc56bb66 4154 push r12
00007ffc`dc56bb68 4156 push r14
00007ffc`dc56bb6a 4157 push r15
00007ffc`dc56bb6c 4881ec60010000 sub rsp,160h
00007ffc`dc56bb73 48c7442458feffffff mov qword ptr [rsp+58h],0FFFFFFFFFFFFFFFEh
00007ffc`dc56bb7c 48897008 mov qword ptr [rax+8],rsi
00007ffc`dc56bb80 48897818 mov qword ptr [rax+18h],rdi
00007ffc`dc56bb84 408af2 mov sil,dl
00007ffc`dc56bb87 4c8d35d2ffffff lea r14,[clr!MarshalNative::GetIUnknownForObjectNative (00007ffc`dc56bb60)]
00007ffc`dc56bb8e 4c89742438 mov qword ptr [rsp+38h],r14
00007ffc`dc56bb93 488364243000 and qword ptr [rsp+30h],0
00007ffc`dc56bb99 48894c2428 mov qword ptr [rsp+28h],rcx
00007ffc`dc56bb9e 83a4249000000000 and dword ptr [rsp+90h],0
00007ffc`dc56bba6 4c89b424a0000000 mov qword ptr [rsp+0A0h],r14
00007ffc`dc56bbae 488d0543646e00 lea rax,[clr!HelperMethodFrame_1OBJ::`vftable' (00007ffc`dcc51ff8)]
00007ffc`dc56bbb5 4889442478 mov qword ptr [rsp+78h],rax
00007ffc`dc56bbba 488d442428 lea rax,[rsp+28h]
00007ffc`dc56bbbf 4889842450010000 mov qword ptr [rsp+150h],rax
00007ffc`dc56bbc7 488d8c24a8000000 lea rcx,[rsp+0A8h]
00007ffc`dc56bbcf e81c93f1ff call clr!LazyMachStateCaptureState (00007ffc`dc484ef0)
00007ffc`dc56bbd4 488d4c2478 lea rcx,[rsp+78h]
00007ffc`dc56bbd9 e85293f1ff call clr!HelperMethodFrame::Push (00007ffc`dc484f30)
00007ffc`dc56bbde 488b8c2498000000 mov rcx,qword ptr [rsp+98h]
00007ffc`dc56bbe6 4533ff xor r15d,r15d
00007ffc`dc56bbe9 4532e4 xor r12b,r12b
00007ffc`dc56bbec 8a0546749200 mov al,byte ptr [clr!g_StackProbingEnabled (00007ffc`dce93038)]
00007ffc`dc56bbf2 84c0 test al,al
00007ffc`dc56bbf4 741a je clr!MarshalNative::GetIUnknownForObjectNative+0xb0 (00007ffc`dc56bc10)
00007ffc`dc56bbf6 e8d1652400 call clr!DefaultRetailStackProbeWorker (00007ffc`dc7b21cc)
00007ffc`dc56bbfb 8a0537749200 mov al,byte ptr [clr!g_StackProbingEnabled (00007ffc`dce93038)]
00007ffc`dc56bc01 84c0 test al,al
00007ffc`dc56bc03 740b je clr!MarshalNative::GetIUnknownForObjectNative+0xb0 (00007ffc`dc56bc10)
00007ffc`dc56bc05 488d4c2448 lea rcx,[rsp+48h]
00007ffc`dc56bc0a e885762400 call clr!SOIntolerantTransitionHandler::CtorImpl (00007ffc`dc7b3294)
00007ffc`dc56bc0f 90 nop
00007ffc`dc56bc10 48837c242800 cmp qword ptr [rsp+28h],0
00007ffc`dc56bc16 750c jne clr!MarshalNative::GetIUnknownForObjectNative+0xc4 (00007ffc`dc56bc24)
00007ffc`dc56bc18 488d0db9767700 lea rcx,[clr!`string' (00007ffc`dcce32d8)]
00007ffc`dc56bc1f e8c8453a00 call clr!RealCOMPlusThrowArgumentNull (00007ffc`dc9101ec)
00007ffc`dc56bc24 b901000000 mov ecx,1
00007ffc`dc56bc29 e82e1ff2ff call clr!EnsureComStarted (00007ffc`dc48db5c)
00007ffc`dc56bc2e 4084f6 test sil,sil
00007ffc`dc56bc31 7417 je clr!MarshalNative::GetIUnknownForObjectNative+0xea (00007ffc`dc56bc4a)
00007ffc`dc56bc33 488d4c2428 lea rcx,[rsp+28h]
00007ffc`dc56bc38 e873104f00 call clr!MarshalNative::IsObjectInContext (00007ffc`dca5ccb0)
00007ffc`dc56bc3d 85c0 test eax,eax
00007ffc`dc56bc3f 7509 jne clr!MarshalNative::GetIUnknownForObjectNative+0xea (00007ffc`dc56bc4a)
00007ffc`dc56bc41 33ff xor edi,edi
00007ffc`dc56bc43 48897c2430 mov qword ptr [rsp+30h],rdi
00007ffc`dc56bc48 eb19 jmp clr!MarshalNative::GetIUnknownForObjectNative+0x103 (00007ffc`dc56bc63)
00007ffc`dc56bc4a 4533c0 xor r8d,r8d
00007ffc`dc56bc4d 418d5005 lea edx,[r8+5]
00007ffc`dc56bc51 488d4c2428 lea rcx,[rsp+28h]
00007ffc`dc56bc56 e855fdffff call clr!GetComIPFromObjectRef (00007ffc`dc56b9b0)
00007ffc`dc56bc5b 488bf8 mov rdi,rax
00007ffc`dc56bc5e 4889442430 mov qword ptr [rsp+30h],rax
00007ffc`dc56bc63 c644244800 mov byte ptr [rsp+48h],0
00007ffc`dc56bc68 803dc973920000 cmp byte ptr [clr!g_StackProbingEnabled (00007ffc`dce93038)],0
00007ffc`dc56bc6f 740b je clr!MarshalNative::GetIUnknownForObjectNative+0x11c (00007ffc`dc56bc7c)
00007ffc`dc56bc71 488d4c2448 lea rcx,[rsp+48h]
00007ffc`dc56bc76 e851762400 call clr!SOIntolerantTransitionHandler::DtorImpl (00007ffc`dc7b32cc)
00007ffc`dc56bc7b 90 nop
00007ffc`dc56bc7c eb1c jmp clr!MarshalNative::GetIUnknownForObjectNative+0x13a (00007ffc`dc56bc9a)
00007ffc`dc56bc7e 408ab42488010000 mov sil,byte ptr [rsp+188h]
00007ffc`dc56bc86 4c8b742438 mov r14,qword ptr [rsp+38h]
00007ffc`dc56bc8b 488b7c2430 mov rdi,qword ptr [rsp+30h]
00007ffc`dc56bc90 4c8b7c2440 mov r15,qword ptr [rsp+40h]
00007ffc`dc56bc95 448a642420 mov r12b,byte ptr [rsp+20h]
00007ffc`dc56bc9a 4584e4 test r12b,r12b
00007ffc`dc56bc9d 7409 je clr!MarshalNative::GetIUnknownForObjectNative+0x148 (00007ffc`dc56bca8)
00007ffc`dc56bc9f 498bd7 mov rdx,r15
00007ffc`dc56bca2 e891211000 call clr!UnwindAndContinueRethrowHelperAfterCatch (00007ffc`dc66de38)
00007ffc`dc56bca7 cc int 3
00007ffc`dc56bca8 488d4c2478 lea rcx,[rsp+78h]
00007ffc`dc56bcad e8be92f1ff call clr!HelperMethodFrame::Pop (00007ffc`dc484f70)
00007ffc`dc56bcb2 488d8c24a8000000 lea rcx,[rsp+0A8h]
00007ffc`dc56bcba e81187f1ff call clr!HelperMethodFrameRestoreState (00007ffc`dc4843d0)
00007ffc`dc56bcbf 85c0 test eax,eax
00007ffc`dc56bcc1 0f85d7feffff jne clr!MarshalNative::GetIUnknownForObjectNative+0x3e (00007ffc`dc56bb9e)
00007ffc`dc56bcc7 488bc7 mov rax,rdi
00007ffc`dc56bcca 4c8d9c2460010000 lea r11,[rsp+160h]
00007ffc`dc56bcd2 498b7320 mov rsi,qword ptr [r11+20h]
00007ffc`dc56bcd6 498b7b30 mov rdi,qword ptr [r11+30h]
00007ffc`dc56bcda 498be3 mov rsp,r11
00007ffc`dc56bcdd 415f pop r15
00007ffc`dc56bcdf 415e pop r14
00007ffc`dc56bce1 415c pop r12
00007ffc`dc56bce3 c3 ret
아래는 Marshal.GetNativeVariantForObject 함수입니다. 내심 GetIUnknownForObject가 내부적으로 GetNativeVariantForObject 함수를 호출한다면 어떤 식으로든 해결책을 욱여넣어보려고 했는데 ^^; 각각 구현이 되어 있어 희망이 사라졌습니다.
clr!MarshalNative::GetNativeVariantForObject:
00007ffc`dca5a8f0 488bc4 mov rax,rsp
00007ffc`dca5a8f3 48895010 mov qword ptr [rax+10h],rdx
00007ffc`dca5a8f7 57 push rdi
00007ffc`dca5a8f8 4156 push r14
00007ffc`dca5a8fa 4157 push r15
00007ffc`dca5a8fc 4881ec60010000 sub rsp,160h
00007ffc`dca5a903 48c7442458feffffff mov qword ptr [rsp+58h],0FFFFFFFFFFFFFFFEh
00007ffc`dca5a90c 48895808 mov qword ptr [rax+8],rbx
00007ffc`dca5a910 48897018 mov qword ptr [rax+18h],rsi
00007ffc`dca5a914 488bfa mov rdi,rdx
00007ffc`dca5a917 488d35d2ffffff lea rsi,[clr!MarshalNative::GetNativeVariantForObject (00007ffc`dca5a8f0)]
00007ffc`dca5a91e 4889742438 mov qword ptr [rsp+38h],rsi
00007ffc`dca5a923 48894c2428 mov qword ptr [rsp+28h],rcx
00007ffc`dca5a928 33db xor ebx,ebx
00007ffc`dca5a92a 899c2490000000 mov dword ptr [rsp+90h],ebx
00007ffc`dca5a931 4889b424a0000000 mov qword ptr [rsp+0A0h],rsi
00007ffc`dca5a939 488d05b8761f00 lea rax,[clr!HelperMethodFrame_1OBJ::`vftable' (00007ffc`dcc51ff8)]
00007ffc`dca5a940 4889442478 mov qword ptr [rsp+78h],rax
00007ffc`dca5a945 488d442428 lea rax,[rsp+28h]
00007ffc`dca5a94a 4889842450010000 mov qword ptr [rsp+150h],rax
00007ffc`dca5a952 488d8c24a8000000 lea rcx,[rsp+0A8h]
00007ffc`dca5a95a e891a5a2ff call clr!LazyMachStateCaptureState (00007ffc`dc484ef0)
00007ffc`dca5a95f 488d4c2478 lea rcx,[rsp+78h]
00007ffc`dca5a964 e8c7a5a2ff call clr!HelperMethodFrame::Push (00007ffc`dc484f30)
00007ffc`dca5a969 488b8c2498000000 mov rcx,qword ptr [rsp+98h]
00007ffc`dca5a971 4c8bf3 mov r14,rbx
00007ffc`dca5a974 448afb mov r15b,bl
00007ffc`dca5a977 8a05bb864300 mov al,byte ptr [clr!g_StackProbingEnabled (00007ffc`dce93038)]
00007ffc`dca5a97d 84c0 test al,al
00007ffc`dca5a97f 741a je clr!MarshalNative::GetNativeVariantForObject+0xab (00007ffc`dca5a99b)
00007ffc`dca5a981 e84678d5ff call clr!DefaultRetailStackProbeWorker (00007ffc`dc7b21cc)
00007ffc`dca5a986 8a05ac864300 mov al,byte ptr [clr!g_StackProbingEnabled (00007ffc`dce93038)]
00007ffc`dca5a98c 84c0 test al,al
00007ffc`dca5a98e 740b je clr!MarshalNative::GetNativeVariantForObject+0xab (00007ffc`dca5a99b)
00007ffc`dca5a990 488d4c2448 lea rcx,[rsp+48h]
00007ffc`dca5a995 e8fa88d5ff call clr!SOIntolerantTransitionHandler::CtorImpl (00007ffc`dc7b3294)
00007ffc`dca5a99a 90 nop
00007ffc`dca5a99b 4885ff test rdi,rdi
00007ffc`dca5a99e 750c jne clr!MarshalNative::GetNativeVariantForObject+0xbc (00007ffc`dca5a9ac)
00007ffc`dca5a9a0 488d0da9892800 lea rcx,[clr!`string' (00007ffc`dcce3350)]
00007ffc`dca5a9a7 e84058ebff call clr!RealCOMPlusThrowArgumentNull (00007ffc`dc9101ec)
00007ffc`dca5a9ac 488b442428 mov rax,qword ptr [rsp+28h]
00007ffc`dca5a9b1 4885c0 test rax,rax
00007ffc`dca5a9b4 741f je clr!MarshalNative::GetNativeVariantForObject+0xe5 (00007ffc`dca5a9d5)
00007ffc`dca5a9b6 488b00 mov rax,qword ptr [rax]
00007ffc`dca5a9b9 3918 cmp dword ptr [rax],ebx
00007ffc`dca5a9bb 7c18 jl clr!MarshalNative::GetNativeVariantForObject+0xe5 (00007ffc`dca5a9d5)
00007ffc`dca5a9bd f60030 test byte ptr [rax],30h
00007ffc`dca5a9c0 7413 je clr!MarshalNative::GetNativeVariantForObject+0xe5 (00007ffc`dca5a9d5)
00007ffc`dca5a9c2 488d1577862800 lea rdx,[clr!`string' (00007ffc`dcce3040)]
00007ffc`dca5a9c9 488d0d883d2800 lea rcx,[clr!`string' (00007ffc`dccde758)]
00007ffc`dca5a9d0 e8ff55ebff call clr!RealCOMPlusThrowArgumentException (00007ffc`dc90ffd4)
00007ffc`dca5a9d5 66891f mov word ptr [rdi],bx
00007ffc`dca5a9d8 488d442428 lea rax,[rsp+28h]
00007ffc`dca5a9dd 4889442430 mov qword ptr [rsp+30h],rax
00007ffc`dca5a9e2 488bd7 mov rdx,rdi
00007ffc`dca5a9e5 488d4c2430 lea rcx,[rsp+30h]
00007ffc`dca5a9ea e82173b1ff call clr!OleVariant::MarshalOleVariantForObject (00007ffc`dc571d10)
00007ffc`dca5a9ef 885c2448 mov byte ptr [rsp+48h],bl
00007ffc`dca5a9f3 381d3f864300 cmp byte ptr [clr!g_StackProbingEnabled (00007ffc`dce93038)],bl
00007ffc`dca5a9f9 740b je clr!MarshalNative::GetNativeVariantForObject+0x116 (00007ffc`dca5aa06)
00007ffc`dca5a9fb 488d4c2448 lea rcx,[rsp+48h]
00007ffc`dca5aa00 e8c788d5ff call clr!SOIntolerantTransitionHandler::DtorImpl (00007ffc`dc7b32cc)
00007ffc`dca5aa05 90 nop
00007ffc`dca5aa06 eb19 jmp clr!MarshalNative::GetNativeVariantForObject+0x131 (00007ffc`dca5aa21)
00007ffc`dca5aa08 33db xor ebx,ebx
00007ffc`dca5aa0a 488bbc2488010000 mov rdi,qword ptr [rsp+188h]
00007ffc`dca5aa12 488b742438 mov rsi,qword ptr [rsp+38h]
00007ffc`dca5aa17 4c8b742440 mov r14,qword ptr [rsp+40h]
00007ffc`dca5aa1c 448a7c2420 mov r15b,byte ptr [rsp+20h]
00007ffc`dca5aa21 4584ff test r15b,r15b
00007ffc`dca5aa24 7409 je clr!MarshalNative::GetNativeVariantForObject+0x13f (00007ffc`dca5aa2f)
00007ffc`dca5aa26 498bd6 mov rdx,r14
00007ffc`dca5aa29 e80a34c1ff call clr!UnwindAndContinueRethrowHelperAfterCatch (00007ffc`dc66de38)
00007ffc`dca5aa2e cc int 3
00007ffc`dca5aa2f 488d4c2478 lea rcx,[rsp+78h]
00007ffc`dca5aa34 e837a5a2ff call clr!HelperMethodFrame::Pop (00007ffc`dc484f70)
00007ffc`dca5aa39 488d8c24a8000000 lea rcx,[rsp+0A8h]
00007ffc`dca5aa41 e88a99a2ff call clr!HelperMethodFrameRestoreState (00007ffc`dc4843d0)
00007ffc`dca5aa46 85c0 test eax,eax
00007ffc`dca5aa48 0f85dcfeffff jne clr!MarshalNative::GetNativeVariantForObject+0x3a (00007ffc`dca5a92a)
00007ffc`dca5aa4e 4c8d9c2460010000 lea r11,[rsp+160h]
00007ffc`dca5aa56 498b5b20 mov rbx,qword ptr [r11+20h]
00007ffc`dca5aa5a 498b7330 mov rsi,qword ptr [r11+30h]
00007ffc`dca5aa5e 498be3 mov rsp,r11
00007ffc`dca5aa61 415f pop r15
00007ffc`dca5aa63 415e pop r14
00007ffc`dca5aa65 5f pop rdi
00007ffc`dca5aa66 c3 ret
[이 글에 대해서 여러분들과 의견을 공유하고 싶습니다. 틀리거나 미흡한 부분 또는 의문 사항이 있으시면 언제든 댓글 남겨주십시오.]