Memory management - C / C++ / MFC Discussion Boards

Re: UnmanagedToManaged Bridge called from unmanaged DLL

Jose Viveiros15-Dec-06 5:24

15-Dec-06 5:24

Hi Mark,

Let me try again (as my last email colapsed some spaces)
works:
Unmanaged App -> UnMng2Mng Bridge -> Assembly DLL

works:
Unmanaged App -> Unmanaged Dll

DoesNot works:
Unmanaged App -> Unmanaged Dll -> UnMng2Mng Bridge -> Assembly DLL

Re: UnmanagedToManaged Bridge called from unmanaged DLL

Mark Salsbery15-Dec-06 6:05

Mark Salsbery

15-Dec-06 6:05

Ok got it, thanks. And what is failing and where? LoadLibrary on the bridge DLL?

Re: UnmanagedToManaged Bridge called from unmanaged DLL

Jose Viveiros15-Dec-06 6:21

Jose Viveiros

15-Dec-06 6:21

LoadLibrary( ) is failing to load the Unmanaged DLL if that DLL links to the unManged2Manged Bridge.
What is strange is that the Brige loads fine if it is loaded directly from the Unmanaged app but it causes problem if you try to use it with a unmanged Dll in between ????

Jose Viveiros

Re: UnmanagedToManaged Bridge called from unmanaged DLL

Mark Salsbery15-Dec-06 6:33

Mark Salsbery

15-Dec-06 6:33

Jose Viveiros wrote:
...if that DLL links to the unManged2Manged Bridge.

How is this "link" done? Through an import library or explicitly with LoadLibrary?
If LoadLibrary, then where are you calling that from in the unmanaged DLL?

Re: UnmanagedToManaged Bridge called from unmanaged DLL

Jose Viveiros15-Dec-06 6:48

Jose Viveiros

15-Dec-06 6:48

hum !
The link between the unmanaged Dll & the Bridge is not done via loadLibrary.
I link in the Bridge.lib and include bridge.h. Is this a problem?

The link between the App & the unmanged Dll does use loadLibrary

Thanks Jose

Jose Viveiros

Re: UnmanagedToManaged Bridge called from unmanaged DLL

Mark Salsbery15-Dec-06 7:41

Mark Salsbery

15-Dec-06 7:41

Jose Viveiros wrote:
I link in the Bridge.lib and include bridge.h. Is this a problem?

Hmm no, it shouldn't be. Calling LoadLibrary from DllMain is a problem - that's why I asked.

1) works:
Unmanaged App -> UnMng2Mng Bridge -> Assembly DLL
2) works:
Unmanaged App -> Unmanaged Dll
3) DoesNot works:
Unmanaged App -> Unmanaged Dll -> UnMng2Mng Bridge -> Assembly DLL

So using method 1 above, you linked using Bridge.lib, correct? If that worked then I would
expect method 3 to work.

Are you doing anything with entry code in your DLLs (DllMain)??

I had problems once with mixed MFC and managed/unmanaged DLLs and found the following article to
be helpful. Although the topic of the article doesn't match the problem, the "Resolution" section
has great info on how to initialize the C runtime (CRT) if you're using it in your DLLs...
You receive linker warnings when you build Managed Extensions for C++ DLL projects[^]

This article has interesting info as well, although it probably doesn't apply to the problem you
are having: Mixed DLL Loading Problem[^]

Re: UnmanagedToManaged Bridge called from unmanaged DLL

Jose Viveiros15-Dec-06 8:36

Jose Viveiros

15-Dec-06 8:36

Hi Mark,
Yes I was also expecting that if method 1 worked method 3 would too. I will check the two articles you send me and I'll let you know if they help me thanks for your help.

Memory management

BlitzPackage14-Dec-06 7:54

BlitzPackage

14-Dec-06 7:54

Greetings,

Let's say I do this:

vector<cmyclass *=""> m_vMyVector;

void SomeFunction(CString strID, bool bStatus)
{
CMyClass * pMyObj = new CMyClass(strID, bStatus);
m_vMyVector.push_back(pMyObj);
pMyObj = NULL;
}

Let's say SomeFunction(...) is in a loop and I create several of these objects. When I call m_vMyVector.clear() will there be a memory leak? In essence, I want to know if I have to go back and call delete on each of the elements in m_vMyVector or will the memory be freed once I call the vector's "clear" method or once the vector is destroyed when the class containing it is destroyed. Also, once I add pMyObj to the vector and reassign the one in the function to point to null, the vector still retains its own valid pointers to the objects in memory, correct?

Thanks for any help or insight you can provide.

Sincerely,
BP

Re: Memory management

Maximilien14-Dec-06 8:12

Maximilien

14-Dec-06 8:12

You will need to loop the vector to delete each item individually, unless you are using auto_ptr thingies.

/// pseudo code.
it = m_vMyVetor.begin();
while (it!= m_vMyVector.end() )
{
 delete *it;
 ++it;
}
m_vMyVector.clear();

and you are correct about the second thing, IMO, assign it back to NULL is not necessary, but a nice touch.

Maximilien Lincourt
Your Head A Splode - Strong Bad

Re: Memory management

BlitzPackage14-Dec-06 8:15

BlitzPackage

14-Dec-06 8:15

Thanks,

I appreciate your response.

BP

Re: Memory management

peterchen14-Dec-06 13:11

peterchen

14-Dec-06 13:11

Hi,

It's not safe to use auto_ptr in a standard container (reference: see e.g. here[^], here[^]

But generally, smart pointers is the way to go. (only auto_ptr is a troubled implementation)

I've written an article about the smart pointer library included with boost - Clickety[^]. That might give you some ideas.

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Re: Memory management

peterchen14-Dec-06 13:12

peterchen

14-Dec-06 13:12

Maximilien wrote:
auto_pt

do me a favor, never use auto_ptr Wink | ;)

Re: Memory management

BlitzPackage14-Dec-06 13:31

BlitzPackage

14-Dec-06 13:31

Thanks PeterChen,

I have heard a lot of great things about boost. Being new to programming, it seems a bit intimidating to use and I am admittedly frightened at the prospect of including it then having to deal with Visual Studio 2003 not playing nice with it. Is boost easy to use?

At any rate, I'll check out your article.

Peace,
BP

Re: Memory management

peterchen14-Dec-06 14:31

peterchen

14-Dec-06 14:31

boost can certainly be intimidating. It is a collection of many different libraries, and some of them are clearly made for advanced program(mer)s.

The smart pointers are an exception. They are (IMO) a very important concept, maybe the first step away from beginner towards advanced programming. They should be easy to understand if you have mastered basic memory management and RAII (using constructors and destructors to acquire and release resources like memory, file handles, ...). I also tried to make the article suitable for beginners (if you read it, please tell me if it works for you Wink | ;)

)

I've been using them with VC6 and VC8, so VC2003 should be no problem. But if boost is still to intimidating, there are many other smart pointer implementations. I recommend boost because they are well designed, flexible, but still fairly simple (a good balance).

Re: Memory management

Maximilien14-Dec-06 14:15

Maximilien

14-Dec-06 14:15

sorry, I thought that would be usefull.

thanks for the heads up.

Maximilien Lincourt
Your Head A Splode - Strong Bad

MFC printing

Milos Djokovic14-Dec-06 6:29

Milos Djokovic

14-Dec-06 6:29

How do I split doc into pages for printing? I have a long multiline string that I want to print. How do I calc number of pages needed to print it? How do I call OnDraw for specific page?

An example would be great.

How i can create Toolbar in my application??

Shah Satish14-Dec-06 4:36

Shah Satish

14-Dec-06 4:36

Hello all.Any body know how i can create toolbaar in my application??

Please if possible then send me code..

Thank you very much..

Shah Satish..

Re: How i can create Toolbar in my application??

Mark Salsbery14-Dec-06 6:15

Mark Salsbery

14-Dec-06 6:15

Just in case you want to know how to use a toolbar control, here's a few links:

Toolbar Control Reference[^]

If you are using MFC...
There's a wrapper class for the toolbar control: CToolBarCtrl Class[^]
There's also the CToolBar Class[^]

Re: How i can create Toolbar in my application??

Hamid_RT14-Dec-06 18:18

Hamid_RT

14-Dec-06 18:18

See here[^]

WhiteSky

Changing Network property programmatically in C++ [modified]

IlyaCher14-Dec-06 4:27

IlyaCher

14-Dec-06 4:27

How can I programmatically change setting in Local Area Connection property using C++ application?

I need to uncheck some property and then check it back. For example File and Printer Sharing for Microsoft Networks.

Thank you.

Ilya

-- modified at 16:03 Wednesday 20th December, 2006

Error

Alex_Y14-Dec-06 4:24

Alex_Y

14-Dec-06 4:24

If you getting error like that

error C2872: 'IXMLDOMParseErrorPtr' : ambiguous symbol
could be 'c:\program files\microsoft visual studio 8\vc\include\comdefsp.h(1263) : _com_ptr_t<_IIID> IXMLDOMParseErrorPtr'
1> with
1> [
1> _IIID=_com_IIID<ixmldomparseerror,& _guid_3efaa426_272f_11d2_836f_0000f87a7782="">
1> ]
1> or '.\debug\msxml3.tlh(250) : MSXML2::IXMLDOMParseErrorPtr'

What would be correct resolution

1. instead of
IXMLDOMParseErrorPtr spErr = pXMLDom->parseError;
use
::IXMLDOMParseErrorPtr spErr = pXMLDom->parseError;

Or use
MSXML2::IXMLDOMParseErrorPtr spErr = pXMLDom->parseError;

Re: Error

Alex_Y14-Dec-06 5:28

Alex_Y

14-Dec-06 5:28

Answer myself MSXML2::

Re: Error

toxcct14-Dec-06 6:20

toxcct

14-Dec-06 6:20

i don't know if it's your case, but it's commonly bad practice to use a using namespace directive, because of such problems of ambiguousness...

Don't know where to start ?
Refer the Forums Guidelines and ask a friend

[VisualCalc 3.0][Flags Beginner's Guide]

Re: Error

Alex_Y14-Dec-06 7:47

Alex_Y

14-Dec-06 7:47

I know, man I know. It was too many places to correct, so I was trying to be smart as Smile | :)

I found that decls. in comdef is different than in msxml*.tlh, so I decided not to use defaults.

Thanks, anyway.

ComboBox problem

Like2Byte14-Dec-06 3:38

Like2Byte

14-Dec-06 3:38

Hi, I have a few comboboxes on a form. Let's name them LHS (left hand side) and RHS. Whenever I click LHS, I want RHS to reset to it's 0th element.

However, when I click an element in LHS, LHS resets to it's 0th element but will still show the proper items in RHS even though LHS is reset to it's 0th element. There are no pointers to objects being used.

What could be a culprit of this problem? Some windows message? I checked the message maps in the class wizard and combo messages are cleared (except CBN_SELCHANGE, of course).

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.