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Hi all,
I was wodering if it is possible to pass values to a thread function without calling _beginthread() for a second time. For example, a thread is created and the thread performs it's tasks, now the thread must perform the same task but this other data, and one doesn't want to create a new thread again. Is this possible ???
Many Thanks
Regards,
The only programmers that are better than C programmers are those who code in 1's and 0's..... 
Programm3r
My Blog: ^_^
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Yes: there are several ways to do that. In general, what I do is a thread that simply calls a member function of a class to do some processing. The class is passed as an argument to the thread function.
So, as the function is a member of the class, you have access to all the members of the class and you can modify them. Of course, you need to secure this with synchronization objects (critical sections, mutexes, ...) to avoid that a same 'member' is accessed at the same time by two different threads.
I hope it makes sense.
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Thanks Cedric, yes it makes sense, kinda. If I may be so bold as to ask for an example if it is possible.
Many Thanks
The only programmers that are better than C programmers are those who code in 1's and 0's.....
Programm3r
My Blog: ^_^
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Programm3r wrote: If I may be so bold as to ask for an example if it is possible.
Something like this:
class CThread
{
public:
CThread();
virtual ~CThread();
void StartThread();
void ThreadFunc();
HANDLE m_hThread;
};
DWORD WINAPI ThreadProc(LPVOID lpParam)
{
CThread* pThread = (CThread*)lpParam;
if (pThread)
pThread->ThreadFunc();
return 0;
}
CThread::CThread()
{
}
CThread::~CThread()
{
}
void CThread::StartThread()
{
m_hThread = CreateThread(NULL,0,ThreadProc,this,0,NULL);
}
void CThread::ThreadFunc()
{
}
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Hi,
I have a web based application in which we have 8 ocx for displaying images.
Currently images are loaded from CD .But now we want to allocate some memory in some of the 8 ocx we have and in this memory we will save maximum files that we could.
Then we want to access this memory buffer using cmemfile.
So we need to create a common memory which can be accessed by all the ocx on the page.
I dont know how to create such memory? And then how to access the memory through different ocx.
Please provide me some inputs on this..
Surendra Vishwkarma
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You might want to look up the CoTaskMemAlloc function and also Memory Mapped Files. Your biggest problem is likely to be browser security. It will not like your embedded controls accessing memory outside their normal scope. You might even have to consider replacing the OCX with Javascript but hopefully not .
It should be possible to write script on the page which can access the controls and negotiate between them which one will own/create a memory mapped file and then communicate it's handle to the other controls.
Nothing is exactly what it seems but everything with seems can be unpicked.
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Hi,
I have a Win32 Console Application which is throwing the Debug Assertion Failed! .. _CrtIsValidHeapPointer( pUserData ) and followed by a Debug Assertion Failed! .. _BLOCK_TYPE_IS_VALID(pHead->nBlockUse).
After I did a Step by Step Debug strangely what I saw was it is throwing error once it is exittin the main function.
Unlike any character pointers and deletion of heap without its references as of when generally this error occurs I have no such instances.
please could you suggest a probable solution to this. please help.
There are only two kinds of people who are really fascinating-people who know absolutely everything, and people who know absolutely nothing.
Oscar Wilde (1854-1900)
Regards...
Shouvik
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Looks like you are trying to delete the same pointer twice, or trying to delete something which is not a pointer to a heap based object.
If you can post some of the code, then we can help.
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The normal debug configuration of a VS C++ project checks the heap hasn't been corrupted when you exit. If these assertions fire, the heap has been corrupted.
This is a wild-write bug. Somewhere, you're using a bad pointer, or have made a mistake in pointer calculation, or allocated too little space for a buffer, or written off the end of a buffer. These are very hard to track down. Ensure that you always initialize pointers to NULL or to a real value, so you don't get random stack garbage that could point anywhere.
If it's consistently the same address, you can use a data breakpoint to see when the data at that address changes. See 'data breakpoints' in MSDN Library.
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according to the following call stack
<br />
NTDLL! 7c901230() <br />
NTDLL! 7c96cd80() <br />
NTDLL! 7c960af8() <br />
KERNEL32! 7c85e9cf() <br />
_CrtIsValidHeapPointer(const void * 0x00032b78) line 1697<br />
_free_dbg_lk(void * 0x00032b78, int 1) line 1044 + 9 bytes <br />
_free_dbg(void * 0x00032b78, int 1) line 1001 + 13 bytes operator <br />
delete(void * 0x00032b78) line 351 + 12 bytes <br />
CString::FreeData() line 146 + 15 bytes <br />
CString::~CString() line 213 $E155() + 34 bytes <br />
doexit(int 0, int 0, int 0) line 353 <br />
exit(int 0) line 279 + 13 bytes <br />
mainCRTStartup() line 345 <br />
KERNEL32! 7c816fd7()<br />
It is clear the error was occuring tryin to free the CString objects which incidentally I had made global due to the requirements. Hence I refactored my application and passed them as reference.
What I inferred from the situation is that while tryin to free up the Cstring memory it encountered that the heap had already been unintiallized. however it is still unclear to me how was the heap cleared before even C Runtime tried to unregister it. I never explicitly have defined any destructors.
There are only two kinds of people who are really fascinating-people who know absolutely everything, and people who know absolutely nothing.
Oscar Wilde (1854-1900)
Regards...
Shouvik
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HELLO to every one..
my question is if i click a menu item from IDR_MAINFRAME window MENU BAR ,i have to be switched to IDR_MENU1 window..
plz help me..
vikram..
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You could create a handler for that menu item, and inside it, call SetMenu ?
Sounds like a potentially bad design though, so I hope you have a really good reason for doing it this way.
Iain.
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I was thinking about your question but I dont know your questions is advance or I dont understand your question.
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To load a plugin from an application - the ATL/COM connection points are used for communication and handling events between host and plugin. If i were to add a second plugin which would load all dlls from a different path and replicating the mechanism of the first plugin, do i need to do any handling for memory management or threading issues? The two plugins will not communicate to one another, and user would switch between the plugins as necessary but the dlls for both plugins will be loaded at the start of the application and unloaded only when application is shutdown.Am not clear if i should inbuild any mechanism for threading or memory ownership issues? Could you also point me to a reference article if any?
Thanks
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The issues you've mentioned don't relate directly to memory ownership or threading so it's a little difficult to give an answer. Your new plugin will need to follow the same threading model as the old one because that is what the client expects. It will need to manage parameter memory ownership the same way as the old one because that is what the client expects.
Also remember that if you link your new DLL statically to the C Runtime e.g. LIBCMT then it will get its own heap. If you link it dynamically with MSVCRT then it will share a heap with the client if and only if the client also links to the CRT dynamically.
Careful examination of the interfaces you're implementing, some guesswork and a lot of testing should get you there 
Nothing is exactly what it seems but everything with seems can be unpicked.
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Hi
I am creating an object using new.
But when the control passes to the Ctor.Its not executing any of the lines in Ctor.
I have set break point in every line of Ctor.
CStateDescription::CStateDescription()
{ //Control comes her
int i = 10;
BOOL boo1 = FALSE;
DWORD dwFlashPictureRate = FlashingMedium; // medium
BOOL boo = FALSE;
//Then the control passes here directly. i is assigned as 0.and others garbage value.
}
Whats the problem here
-- modified at 22:37 Tuesday 19th June, 2007
VIBIN
"Fool's run away,where angle's fear to tread"
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vibindia wrote: CStateDescription::CStateDescription()
{ //Control comes her
int i = 10;
BOOL boo1 = FALSE;
DWORD dwFlashPictureRate = FlashingMedium; // medium
BOOL boo = FALSE;
//Then the control passes here directly. i is assigned as 0.and others garbage value.
}
All the above variables are local to the contructor's scope. Thus, they don't exist when the constructor returns.
You need to do something like the following:
CStateDescription::CStateDescription()
{
i = 10;
boo1 = FALSE;
dwFlashPictureRate = FlashingMedium;
boo = FALSE;
}
Or better yet:
CStateDescription::CStateDescription()
: i(10), boo1(FALSE), dwFlashPictureRate(FlashingMedium), boo(FALSE)
{}
-- modified at 22:59 Tuesday 19th June, 2007
"We make a living by what we get, we make a life by what we give." --Winston Churchill
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Not sure but I think it may be the cause.
Try to rebuild the application after clean all.
And my stupid thinking says me that you are trying to debug the application in Release mode 
Regards
Anil
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_anil_ wrote: And my stupid thinking says me that you are trying to debug the application in Release mode
You can so long as you have configured your release build to produce a .PDB symbolic information file.
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Basically, in what I'm programming, I use the WndProc function to direct input at my window, however, WndProc must be either a global or a static function. When a function is static, it can only access static members, unless they are created within the scope of the static function. There are two things I can do.
1 - Make the non-static members that I want to call static.
2 - Use static GetInstance() methods to get static instances of the classes which contain my members, and use those classes to access the members.
1 is a lot more arbitrary -- you can apply static to anything, and everything will become static. 2 is a lot cleaner, as I may have to access many members of my class and it would be easier to just get one static instance than make everything in that class static. I'm thinking of going with 2, as the classes of which I'd need to get an instance of, are singletons, so it's not even much of a problem, however, does anyone else have this obsessive anti-static dilemma, where they just want to get rid of everything that's static for the sake of object-oriented programming?
(Note: by the way, if anyone knows how to do these kinds of things without going static at all, that would be even better!)
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The WindowProc needs to be static but that's it.
I try to find any way I can in callbacks to get a pointer passed in there. That pointer is always
a pointer to an object relevent to the callback. One cast, one call, and you're back in non-
static OOP land
It's no different with a windowproc - it's easy to add a pointer to an HWND.
I guess that's your method 2, except the GetInstance method IS the callback.
My 2 cents,
Mark
"Posting a VB.NET question in the C++ forum will end in tears." Chris Maunder
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Yes, there is a way to do that: register the pointer to your object (the this pointer) with SetWindowLong[^] (with the type GWL_USERDATA for the nIndex). Once your WndProc is called, you can retrieve your object pointer by calling GetWindowLong, cast it back to your class and you can call a specific non-static member function to handle the message.
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Interesting, I'll give that a try.
Thanks.
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