Memory leak in interop - C# / C Sharp

Trokey

I am making interop calls to an object in a .NET component from a C++
program and am leaking memory... the following is some sample code:

////////////////////////////////////////
// .NET component (Test)
////////////////////////////////////////

// interface
[InterfaceType(ComInterfaceType.InterfaceIsDual)]
[Guid("D3DF5658-3D3F-436b-B6A6-F10E77AE3F5F")]
public interface IDotNetInterface
{
int getString(string aParam1, string aParam2, out string aValue);
}

// class
[ClassInterface(ClassInterfaceType.None)]
[ProgId("Test.DotNetInterface")]
public class DotNetInterface : IDotNetInterface
{
public int getString(string aParam1, string aParam2, out string aValue)
{
aValue = "some text";
GC.Collect();
return 1;
}
}

///////////////////////////////////
// C++ program
///////////////////////////////////

#import "Test.tlb" no_namespace named_guids

int _tmain(int argc, _TCHAR* argv[])
{
CoInitializeEx(NULL, COINIT_MULTITHREADED);

IDotNetInterfacePtr pPtr = IDotNetInterface(__uuidof(DotNetInterface));
pPtr->AddRef();

_bstr_t lParam1 = "1";
_bstr_t lParam2 = "2";

BSTR lValue;
int lResult = pPtr->getString(lParam1, lParam2, &lValue); // <-- LEAK!!

pPtr->Release();
pPtr = NULL;
}
I've tried all sorts of things (trying to explicitly release the BSTR
memory, etc.), but no effect. What is causing this leak, and how do I solve
it???

Thanks in advance,
Matt

Nov 15 '05 #1

Subscribe Post Reply

2376

Nicholas Paldino [.NET/C# MVP]

Trokey,

I don't see how the runtime is causing the leak. If anything, you need
to call SysFreeString to free the string.

You can also use a CComBSTR class and it will handle this automatically.

Also, you don't need to call the static Collect method on the GC class.

What do you have to support that there is a leak?
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"Trokey" <ma********@hotmail.com> wrote in message
news:bp*************@ID-203151.news.uni-berlin.de...

I am making interop calls to an object in a .NET component from a C++
program and am leaking memory... the following is some sample code:

////////////////////////////////////////
// .NET component (Test)
////////////////////////////////////////

// interface
[InterfaceType(ComInterfaceType.InterfaceIsDual)]
[Guid("D3DF5658-3D3F-436b-B6A6-F10E77AE3F5F")]
public interface IDotNetInterface
{
int getString(string aParam1, string aParam2, out string aValue);
}

// class
[ClassInterface(ClassInterfaceType.None)]
[ProgId("Test.DotNetInterface")]
public class DotNetInterface : IDotNetInterface
{
public int getString(string aParam1, string aParam2, out string aValue)
{
aValue = "some text";
GC.Collect();
return 1;
}
}

///////////////////////////////////
// C++ program
///////////////////////////////////

#import "Test.tlb" no_namespace named_guids

int _tmain(int argc, _TCHAR* argv[])
{
CoInitializeEx(NULL, COINIT_MULTITHREADED);

IDotNetInterfacePtr pPtr = IDotNetInterface(__uuidof(DotNetInterface)); pPtr->AddRef();

_bstr_t lParam1 = "1";
_bstr_t lParam2 = "2";

BSTR lValue;
int lResult = pPtr->getString(lParam1, lParam2, &lValue); // <-- LEAK!!
pPtr->Release();
pPtr = NULL;
}
I've tried all sorts of things (trying to explicitly release the BSTR
memory, etc.), but no effect. What is causing this leak, and how do I solve it???

Thanks in advance,
Matt

Nov 15 '05 #2

SCG

>> If anything, you need to call SysFreeString to free the string.

Absolutely. I believe this may be your issue.
"Nicholas Paldino [.NET/C# MVP]" <mv*@spam.guard.caspershouse.com> wrote in
message news:u5**************@TK2MSFTNGP11.phx.gbl...

Trokey,

I don't see how the runtime is causing the leak. If anything, you need to call SysFreeString to free the string.

You can also use a CComBSTR class and it will handle this automatically.
Also, you don't need to call the static Collect method on the GC class.
What do you have to support that there is a leak?
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"Trokey" <ma********@hotmail.com> wrote in message
news:bp*************@ID-203151.news.uni-berlin.de...
I am making interop calls to an object in a .NET component from a C++
program and am leaking memory... the following is some sample code:

////////////////////////////////////////
// .NET component (Test)
////////////////////////////////////////

// interface
[InterfaceType(ComInterfaceType.InterfaceIsDual)]
[Guid("D3DF5658-3D3F-436b-B6A6-F10E77AE3F5F")]
public interface IDotNetInterface
{
int getString(string aParam1, string aParam2, out string aValue);
}

// class
[ClassInterface(ClassInterfaceType.None)]
[ProgId("Test.DotNetInterface")]
public class DotNetInterface : IDotNetInterface
{
public int getString(string aParam1, string aParam2, out string aValue) {
aValue = "some text";
GC.Collect();
return 1;
}
}

///////////////////////////////////
// C++ program
///////////////////////////////////

#import "Test.tlb" no_namespace named_guids

int _tmain(int argc, _TCHAR* argv[])
{
CoInitializeEx(NULL, COINIT_MULTITHREADED);

IDotNetInterfacePtr pPtr =

IDotNetInterface(__uuidof(DotNetInterface));
pPtr->AddRef();

_bstr_t lParam1 = "1";
_bstr_t lParam2 = "2";

BSTR lValue;
int lResult = pPtr->getString(lParam1, lParam2, &lValue); // <--

LEAK!!

pPtr->Release();
pPtr = NULL;
}
I've tried all sorts of things (trying to explicitly release the BSTR
memory, etc.), but no effect. What is causing this leak, and how do I

solve
it???

Thanks in advance,
Matt

Nov 15 '05 #3

Trokey

I've tried all these things, but no difference... I know there is a leak
because I monitor the private bytes in perfmon and the memory allocated by
the getString call is never released.

Matt

"Nicholas Paldino [.NET/C# MVP]" <mv*@spam.guard.caspershouse.com> wrote in
message news:u5**************@TK2MSFTNGP11.phx.gbl...

Trokey,

I don't see how the runtime is causing the leak. If anything, you need to call SysFreeString to free the string.

You can also use a CComBSTR class and it will handle this automatically.
Also, you don't need to call the static Collect method on the GC class.
What do you have to support that there is a leak?
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"Trokey" <ma********@hotmail.com> wrote in message
news:bp*************@ID-203151.news.uni-berlin.de...
I am making interop calls to an object in a .NET component from a C++
program and am leaking memory... the following is some sample code:

////////////////////////////////////////
// .NET component (Test)
////////////////////////////////////////

// interface
[InterfaceType(ComInterfaceType.InterfaceIsDual)]
[Guid("D3DF5658-3D3F-436b-B6A6-F10E77AE3F5F")]
public interface IDotNetInterface
{
int getString(string aParam1, string aParam2, out string aValue);
}

// class
[ClassInterface(ClassInterfaceType.None)]
[ProgId("Test.DotNetInterface")]
public class DotNetInterface : IDotNetInterface
{
public int getString(string aParam1, string aParam2, out string aValue) {
aValue = "some text";
GC.Collect();
return 1;
}
}

///////////////////////////////////
// C++ program
///////////////////////////////////

#import "Test.tlb" no_namespace named_guids

int _tmain(int argc, _TCHAR* argv[])
{
CoInitializeEx(NULL, COINIT_MULTITHREADED);

IDotNetInterfacePtr pPtr =

IDotNetInterface(__uuidof(DotNetInterface));
pPtr->AddRef();

_bstr_t lParam1 = "1";
_bstr_t lParam2 = "2";

BSTR lValue;
int lResult = pPtr->getString(lParam1, lParam2, &lValue); // <--

LEAK!!

pPtr->Release();
pPtr = NULL;
}
I've tried all sorts of things (trying to explicitly release the BSTR
memory, etc.), but no effect. What is causing this leak, and how do I

solve
it???

Thanks in advance,
Matt

Nov 15 '05 #4

Willy Denoyette [MVP]

int _tmain(int argc, _TCHAR* argv[])
{
CoInitialize(NULL);
IDotNetInterfacePtr pPtr(__uuidof(DotNetInterface));
_bstr_t lParam1 = "1";
_bstr_t lParam2 = "2";

BSTR lValue;
for (int i=0; i<100000000; i++) {
int lResult = pPtr->getString(lParam1, lParam2, &lValue);
SysFreeString(lValue); // <-- NO LEAK!!
}
}
Willy.

"Trokey" <ma********@hotmail.com> wrote in message
news:bp*************@ID-203151.news.uni-berlin.de...

I've tried all these things, but no difference... I know there is a leak
because I monitor the private bytes in perfmon and the memory allocated by
the getString call is never released.

Matt

"Nicholas Paldino [.NET/C# MVP]" <mv*@spam.guard.caspershouse.com> wrote in message news:u5**************@TK2MSFTNGP11.phx.gbl...
Trokey,

I don't see how the runtime is causing the leak. If anything, you

need
to call SysFreeString to free the string.

You can also use a CComBSTR class and it will handle this

automatically.

Also, you don't need to call the static Collect method on the GC

class.

What do you have to support that there is a leak?
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"Trokey" <ma********@hotmail.com> wrote in message
news:bp*************@ID-203151.news.uni-berlin.de...
I am making interop calls to an object in a .NET component from a C++
program and am leaking memory... the following is some sample code:

////////////////////////////////////////
// .NET component (Test)
////////////////////////////////////////

// interface
[InterfaceType(ComInterfaceType.InterfaceIsDual)]
[Guid("D3DF5658-3D3F-436b-B6A6-F10E77AE3F5F")]
public interface IDotNetInterface
{
int getString(string aParam1, string aParam2, out string aValue);
}

// class
[ClassInterface(ClassInterfaceType.None)]
[ProgId("Test.DotNetInterface")]
public class DotNetInterface : IDotNetInterface
{
public int getString(string aParam1, string aParam2, out string aValue) {
aValue = "some text";
GC.Collect();
return 1;
}
}

///////////////////////////////////
// C++ program
///////////////////////////////////

#import "Test.tlb" no_namespace named_guids

int _tmain(int argc, _TCHAR* argv[])
{
CoInitializeEx(NULL, COINIT_MULTITHREADED);

IDotNetInterfacePtr pPtr =

IDotNetInterface(__uuidof(DotNetInterface));
pPtr->AddRef();

_bstr_t lParam1 = "1";
_bstr_t lParam2 = "2";

BSTR lValue;
int lResult = pPtr->getString(lParam1, lParam2, &lValue); // <--

LEAK!!

pPtr->Release();
pPtr = NULL;
}
I've tried all sorts of things (trying to explicitly release the BSTR
memory, etc.), but no effect. What is causing this leak, and how do I

solve
it???

Thanks in advance,
Matt

Nov 15 '05 #5

Trokey

Thanks everyone... after putting the call in a loop, I can see that
SysFreeString solves the problem.

Matt

"Willy Denoyette [MVP]" <wi*************@pandora.be> wrote in message
news:ek**************@TK2MSFTNGP10.phx.gbl...

int _tmain(int argc, _TCHAR* argv[])
{
CoInitialize(NULL);
IDotNetInterfacePtr pPtr(__uuidof(DotNetInterface));
_bstr_t lParam1 = "1";
_bstr_t lParam2 = "2";

BSTR lValue;
for (int i=0; i<100000000; i++) {
int lResult = pPtr->getString(lParam1, lParam2, &lValue);
SysFreeString(lValue); // <-- NO LEAK!!
}
}
Willy.

"Trokey" <ma********@hotmail.com> wrote in message
news:bp*************@ID-203151.news.uni-berlin.de...
I've tried all these things, but no difference... I know there is a leak
because I monitor the private bytes in perfmon and the memory allocated by the getString call is never released.

Matt

"Nicholas Paldino [.NET/C# MVP]" <mv*@spam.guard.caspershouse.com> wrote

in
message news:u5**************@TK2MSFTNGP11.phx.gbl...
Trokey,

I don't see how the runtime is causing the leak. If anything, you

need
to call SysFreeString to free the string.

You can also use a CComBSTR class and it will handle this

automatically.

Also, you don't need to call the static Collect method on the GC

class.

What do you have to support that there is a leak?
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"Trokey" <ma********@hotmail.com> wrote in message
news:bp*************@ID-203151.news.uni-berlin.de...
> I am making interop calls to an object in a .NET component from a C++ > program and am leaking memory... the following is some sample code:
>
> ////////////////////////////////////////
> // .NET component (Test)
> ////////////////////////////////////////
>
> // interface
> [InterfaceType(ComInterfaceType.InterfaceIsDual)]
> [Guid("D3DF5658-3D3F-436b-B6A6-F10E77AE3F5F")]
> public interface IDotNetInterface
> {
> int getString(string aParam1, string aParam2, out string aValue); > }
>
> // class
> [ClassInterface(ClassInterfaceType.None)]
> [ProgId("Test.DotNetInterface")]
> public class DotNetInterface : IDotNetInterface
> {
> public int getString(string aParam1, string aParam2, out string

aValue)
> {
> aValue = "some text";
> GC.Collect();
> return 1;
> }
> }
>
> ///////////////////////////////////
> // C++ program
> ///////////////////////////////////
>
> #import "Test.tlb" no_namespace named_guids
>
> int _tmain(int argc, _TCHAR* argv[])
> {
> CoInitializeEx(NULL, COINIT_MULTITHREADED);
>
> IDotNetInterfacePtr pPtr =
IDotNetInterface(__uuidof(DotNetInterface));
> pPtr->AddRef();
>
> _bstr_t lParam1 = "1";
> _bstr_t lParam2 = "2";
>
> BSTR lValue;
> int lResult = pPtr->getString(lParam1, lParam2, &lValue); // <--
LEAK!!
>
> pPtr->Release();
> pPtr = NULL;
> }
>
>
> I've tried all sorts of things (trying to explicitly release the BSTR > memory, etc.), but no effect. What is causing this leak, and how do I solve
> it???
>
> Thanks in advance,
> Matt
>
>

Nov 15 '05 #6

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