Re: MFC static variable - C / C++ / MFC Discussion Boards

Re: application scripting advice

CPallini14-Apr-09 22:55

CPallini

14-Apr-09 22:55

I don't know. What exactly do you need to do?
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

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MFC static variable

bhanu_850914-Apr-09 7:44

bhanu_8509

14-Apr-09 7:44

Dear All,

I have a project with so many static variables accessed from one class to another class. I access these static variables by threads.

For example, I access one variable in one thread to change the value and another thread to access it. Both threads are running concurrently. But sometime abruptly the static variable value got changed and it holds a very big value which results in some problem.

I know that I use more static variables and I do mistake in programming but can anyone tell me avoid this kind of problem and why the variable is suddenly holding huge values.

Many thanks in advance.

Kind regards,
Bhanu

Re: MFC static variable

Eytukan14-Apr-09 8:25

Eytukan

14-Apr-09 8:25

Are you sure all those variables are properly synchronized for concurrent accesses?

Starting to think people post kid pics in their profiles because that was the last time they were cute - Jeremy.

Re: MFC static variable

bhanu_850914-Apr-09 8:31

bhanu_8509

14-Apr-09 8:31

Sorry I don't use any synchronization for the variables. But one thread is reading and another thread is writing. Please help me how to synchronize the variables.

Many thanks for your reply.

Re: MFC static variable

Iain Clarke, Warrior Programmer14-Apr-09 8:57

Iain Clarke, Warrior Programmer

14-Apr-09 8:57

It sounds like you read the variable halfway through being changed. So, the variable is not a trivial type (ie, BOOL).

Look at CCriticalSection, it's probably what you need. There's a million and one way to do this though. You could wrap the variable in a class including the CCriticalSection, and write get / set routines that use the critsect.

It really depends on the fine details.

If you have loads of static variables, it makes me suspect your initial design though. May be worth a second look. Does PlaceA need to know details of PlaceB?

Iain.

In the process of moving to Sweden for love (awwww).
If you're in Scandinavia and want an MVP on the payroll (or happy with a remote worker), give me a job! http://cv.imcsoft.co.uk/[^]

Re: MFC static variable

bhanu_850914-Apr-09 9:02

bhanu_8509

14-Apr-09 9:02

Iain Clarke wrote:

If you have loads of static variables, it makes me suspect your initial design though. May be worth a second look. Does PlaceA need to know details of PlaceB?

Yes PlaceA need to know the details of PlaceB. Can you please suggest me a quick way to overcome this problem.

Re: MFC static variable

Iain Clarke, Warrior Programmer14-Apr-09 9:11

Iain Clarke, Warrior Programmer

14-Apr-09 9:11

bhanu_8509 wrote:
Can you please suggest me a quick way to overcome this problem.

No, only the slow way of proper design, and wrapping access to complex variables in critical sections.

Iain.

In the process of moving to Sweden for love (awwww).
If you're in Scandinavia and want an MVP on the payroll (or happy with a remote worker), give me a job! http://cv.imcsoft.co.uk/[^]

Re: MFC static variable

CPallini14-Apr-09 9:19

CPallini

14-Apr-09 9:19

Iain Clarke wrote:
No, only the slow way of proper design, and wrapping access to complex variables in critical sections.

Well said, Euclid, with his "there is no royal road to geometry" is a newbie.
Smile | :)

Re: MFC static variable

Nemanja Trifunovic14-Apr-09 9:02

Nemanja Trifunovic

14-Apr-09 9:02

bhanu_8509 wrote:
I have a project with so many static variables accessed from one class to another class. I access these static variables by threads.

That's your problem. Is it possible in your case to send messages between threads, rather than accessing static variables directly?

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Re: MFC static variable

Rajesh R Subramanian14-Apr-09 20:24

Rajesh R Subramanian

14-Apr-09 20:24

If the variables are not volatile, you're already in trouble. The ideal way would be to synchronize access to the variable using thread synchronization techniques (a critical section would do, as all your threads belong to the same process).

I see you have a lot of things to read up.

It is a crappy thing, but it's life -^ Carlo Pallini

gpedit.msc from VC++

neelu777914-Apr-09 4:25

neelu7779

14-Apr-09 4:25

Hello All,

Can some one please tell me how to access the settings in gpedit.msc using VC++?

I need to set/reset various options from the gpedit.msc.

Thanks in advance.

Re: gpedit.msc from VC++

Michael Schubert14-Apr-09 6:47

Michael Schubert

14-Apr-09 6:47

I think all these options are under "[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Group Policy"

C# / C++ Interop, Odd behaviour from marshalled strings

Mikey_H14-Apr-09 3:50

Mikey_H

14-Apr-09 3:50

Hello,

I am trying some Interop in my application. This is the first time I have had to pass arguments with function calls. I am experiencing some odd results.

// C# Function Call
RenderEngine.LoadNewMesh("BasicMesh", "Pyramid3", 1);

// Managed C++ Wrapper Function
void RenderEngine::LoadNewMesh(String^ meshType, String^ meshName, int nSubsets)
{
	char* cMeshType = (char*)(void*)Marshal::StringToHGlobalAnsi(meshType);
	char* cMeshName = (char*)(void*)Marshal::StringToHGlobalAnsi(meshName);

	m_engineRoot->LoadMesh.LoadNewMesh(cMeshType, cMeshName, nSubsets);
}

// Native C++ Function
void MeshLoader::LoadNewMesh(char* meshType, char* meshName, UINT nSubsets)
{
	//char* 
        m_meshType						= meshType;
	//char* 
        m_meshName						= meshName;
	m_nSubsets						= 0;
	m_nTotalSubsets					        = nSubsets;

	m_pMesh							= new BasicMesh();

        // This message box will display Pyramid3
        MessageBox(0, meshName, 0, 0);

        // This code will not trigger the message box
        if (meshName == "Pyramid3")
                MessageBox(0, (char*)"meshName is Pyramid3", 0, 0);

        // This code will trigger and m_meshName is set directly as Pyramid3
        // if it is not set directly here the call to GetMeshByName later on returns NULL
	if (strcmp(meshName,"Pyramid3") == 0)
		m_meshName = "Pyramid3";
}

// Object is referenced by name here
MeshManager::CreateMesh(m_pMesh, m_meshName);

// Will return NULL if char* is not set directly
MeshManager::GetMeshByName("Pyramid3");

Re: C# / C++ Interop, Odd behaviour from marshalled strings

C^hris L^osinger14-Apr-09 4:35

C^hris L^osinger

14-Apr-09 4:35

Mikey_H wrote:
if (meshName == "Pyramid3")

the value of meshName is the address of the first character of the string. it is not a string itself. in other words, meshName is a pointer, not a string.

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Re: C# / C++ Interop, Odd behaviour from marshalled strings [modified]

Mikey_H14-Apr-09 5:16

Mikey_H

14-Apr-09 5:16

The third condition here will result true, as does the second

if (meshName == "Pyramid3")
        MessageBox(0, (char*)"meshName is Pyramid3", 0, 0);

if (strcmp(meshName,"Pyramid3") == 0)
	m_meshName = "Pyramid3";

if (m_meshName == "Pyramid3")
        MessageBox(0, (char*)"m_meshName is Pyramid3", 0, 0);

modified on Tuesday, April 14, 2009 12:35 PM

Re: C# / C++ Interop, Odd behaviour from marshalled strings [modified]

C^hris L^osinger14-Apr-09 5:29

C^hris L^osinger

14-Apr-09 5:29

right, because you've assigned meshName to m_meshName, and i assume m_meshName is a string object of some kind, one with an overloaded "==" operator which knows how to compare a C-style (char*) string to its contents. (CString or std::string?)

the problem with the first remains: you cannot compare a pointer to a static string. that's not how C-style strings work. and that's why strcmp exists.

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modified on Tuesday, April 14, 2009 11:39 AM

Re: C# / C++ Interop, Odd behaviour from marshalled strings

Iain Clarke, Warrior Programmer14-Apr-09 5:33

Iain Clarke, Warrior Programmer

14-Apr-09 5:33

There's no overloading if his comments are right - they're char *'s.

So, it's simpler than you thought... See http://www.codeproject.com/script/Forums/View.aspx?fid=1647&msg=3003509[^] for more.

Iain.

In the process of moving to Sweden for love (awwww).
If you're in Scandinavia and want an MVP on the payroll (or happy with a remote worker), give me a job! http://cv.imcsoft.co.uk/[^]

Re: C# / C++ Interop, Odd behaviour from marshalled strings

C^hris L^osinger14-Apr-09 5:40

C^hris L^osinger

14-Apr-09 5:40

ah. you're right. i missed that comment.

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Re: C# / C++ Interop, Odd behaviour from marshalled strings

Iain Clarke, Warrior Programmer14-Apr-09 5:30

Iain Clarke, Warrior Programmer

14-Apr-09 5:30

The second comparison is the correct one.

Two facts you need to know.

1/ m_meshName is a pointer to character. Underneath, it's an integer holding an address in RAM.
2/ The compiler has seen two constant strings in your code, but only bothers to store one copy of the string "Pyramid3" in it's data segment.

So, the strcmp works as intended, and makes m_meshName point to the constant string in your code.

The 3rd comparison works by luck, as m_meshName is still pointing to that string. This is because your compiler is being efficient, it is not because your code is correct.

You are lucky.

If this doesn't sink in (it's hard until you have a lightbulb moment), I can recommend reading The Complete Guide to C++ Strings, Part I - Win32 Character Encodings[^]

Iain.

In the process of moving to Sweden for love (awwww).
If you're in Scandinavia and want an MVP on the payroll (or happy with a remote worker), give me a job! http://cv.imcsoft.co.uk/[^]

Re: C# / C++ Interop, Odd behaviour from marshalled strings

Mikey_H14-Apr-09 6:34

Mikey_H

14-Apr-09 6:34

Iain Clarke wrote:
If this doesn't sink in (it's hard until you have a lightbulb moment)

My lightbulb is on a dimmer switch... I think I understand what you are saying in your reply. I have just read Part 1, will follow up with Part 2 tomorrow, as it is 4.26am.

If my understanding is correct I will be making a lot of changes to my application once I figure this out.

Thank you both for your replies. Thumbs Up | :thumbsup:

Having a generic function GetProcAddress for both unicode and ascii builds - fails in release mode

Priya_Sundar14-Apr-09 3:43

Priya_Sundar

14-Apr-09 3:43

Hi All,

I am having a common code snippet to be compiled in VC6 and in Embedded vc++(CE). Right now i am working with vc6 part.

void* CNewClass::GetProcAddress1(HMODULE hModule, LPCTSTR lpFuncName)
{
	USES_CONVERSION;//for ATL, to use A2W declare this first  

	#ifdef _WINCE	//for wince
		LPCWSTR lpUnicodeFuncName = A2W( lpFuncName );
		return(GetProcAddress(hModule, lpUnicodeFuncName));
	#else // for vc6
		LPCSTR lpAsciiFuncName = (LPCSTR)W2A( lpFuncName );
		return (GetProcAddress(hModule, lpAsciiFuncName));
	#endif
}

Problem: This function (GetProcAddress) returns 0/fails in release mode. It works fine in debug mode.

General Info: The function GetProcAddress resolves to GetProcAddressA or GetProcAddressW based on the build(ascii or unicode) in EVC++ whereas in vc6, it is GetProcAddress only (simlar to GetProcAddressA with LPCSTR as second parameter).

Also just FYI: http://blog.voidnish.com/?p=70[^]

I tried lot of ways to typecastings.. but didnot work. Please help.

Priya Sundar

Re: Having a generic function GetProcAddress for both unicode and ascii builds - fails in release mode

Iain Clarke, Warrior Programmer14-Apr-09 4:07

Iain Clarke, Warrior Programmer

14-Apr-09 4:07

Should the

LPCSTR lpAsciiFuncName = (LPCSTR)W2A( lpFuncName );

line be:

LPCSTR lpAsciiFuncName = (LPCSTR)T2A( lpFuncName );

?

That may not be the source of your trouble, but it won't help...

Iain.

In the process of moving to Sweden for love (awwww).
If you're in Scandinavia and want an MVP on the payroll (or happy with a remote worker), give me a job! http://cv.imcsoft.co.uk/[^]

Re: Having a generic function GetProcAddress for both unicode and ascii builds - fails in release mode

CPallini14-Apr-09 5:47

CPallini

14-Apr-09 5:47

On my system this code (following Iain's suggestion), compiled with VC6 works fine both on Debug and Release build

LPCSTR lpAsciiFuncName = T2A( lpFuncName );
return (GetProcAddress(hModule, lpAsciiFuncName));

Re: Having a generic function GetProcAddress for both unicode and ascii builds - fails in release mode

Priya_Sundar14-Apr-09 17:12

Priya_Sundar

14-Apr-09 17:12

Hi,

Still it is not working after using T2A().

And fyi I am compiling my application(vc6) in UNICODE!

Could you please show me your function call?

The below is my function call:

CString CompletePathOfDll ="E:\\sample.dll";
HINSTANCE DllHandle = LoadLibrary(CompletePathOfDll);//loads the dll successfully

if (DllHandle != NULL)
{
	int IsCorrectDll=(int)GetProcAddress1(DllHandle ,TEXT("Get_Data_Function"));
	if(IsCorrectDll>0)
	{
	    //do something
	}
}

Thanks.

Priya Sundar

how to create new thread

hemlat14-Apr-09 3:39

hemlat

14-Apr-09 3:39

Hi,
I need to create new thread if I click on particular button in my MFC application.I have added following code.

AfxBeginThread( CRuntimeClass* pfnThreadProc,LPVOID pParam, 
		int nPriority = THREAD_PRIORITY_NORMAL,UINT nStackSize = 0, 
		DWORD dwCreateFlags = 0,LPSECURITY_ATTRIBUTES lpSecurityAttrs = NULL);
UINT CTestcycleDlg::pfnThreadProc(LPVOID pParam )
{
}

I am getting errors one of thoes error is

error C2275: 'CRuntimeClass' : illegal use of this type as an expression <br />

I have created user interface thread.Is it correct.Where I need to close thread and how to close

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