C / C++ / MFC

13-Mar-08 12:06

In a dll, i start a thread using _beginthread like:

_beginthread(Mythread,0,LPVOID(this));

void MyThread(LPVOID pVoid)
{

CMyClass* pClass = static_cast<CMyClass*>(pVoid);
pClass->SetValue(1);

}

Everything works nicely until i try to access one of the member vars from CMyClass. The app begins to lock up on me. I may be missing something fundamental here. Anyone have any thoughts?

Mark Salsbery13-Mar-08 13:29

Mark Salsbery

13-Mar-08 13:29

There's nothing in the code you've shown that looks like it would
lock anything up. Actually the thread shown could finish before
_beginthread() completes on the calling thread Smile | :)

You can examine the call stack of all the threads in the debugger when it's
locked up and maybe that will help determine the offending code.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Peter Weyzen13-Mar-08 13:57

Peter Weyzen

13-Mar-08 13:57

Here's my fundamental question about your thread....

You're now accessing "this" from your thread?
And are you also accessing "this" from the thread that created it?

Are you employing appropriate locks to protect "this"?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<br />
Peter Weyzen<br />
Staff Engineer<br />
<a href="http://www.soonr.com">SoonR Inc -- PC Power delivered to your phone</a>

Eytukan13-Mar-08 16:11

Eytukan

13-Mar-08 16:11

LCI wrote:
Everything works nicely until i try to access one of the member vars from CMyClass.

You mean, if you try to access a specific member or "ANY" member?

OK,. what country just started work for the day ? The ASP.NET forum is flooded with retarded questions. -Christian Graus

Best wishes to Rexx[^]

LCI14-Mar-08 2:32

14-Mar-08 2:32

Any member this seems to have an issue with .

Rajkumar R14-Mar-08 3:02

Rajkumar R

14-Mar-08 3:02

what do you mean by "The app begins to lock up on you". if you are human being i don't know whether you are using such an advanced technology Smile | :)

The bad cast can endup in undefined state, can you please post what you are passing to the thread?

LCI14-Mar-08 5:05

14-Mar-08 5:05

Here is what i have:
The app freezes in Class B which is a dll. I know that there is something
wrong with the parameter that the thread is receiving in that dll, but i cannot figure it out.

ClassA
{
CWinThread* pThreadA[3] = {NULL};
CClassA::BeginAllThreads()
{
CClassC* pApp = reinterpret_cast<cclassc*>(AfxGetApp());

if (NULL == pThreadA[i])
{
pThreadA[i] = AfxBeginThread(ThreadGetOne,
(LPVOID)pApp->m_arrPtr[i],
THREAD_PRIORITY_NORMAL,
0,
CREATE_SUSPENDED,
NULL);
pThreadA[i]->m_AutoDelete = FALSE;
pThreadA[i]->ResumeThread();

pApp->arrPtr[i]->StartThread();
}

}
void ThreadGetOne(LPVOID pVoid)
{

CClassB* pPointer = (CClassB*)pVoid
while (TRUE)
{
pPointer->Readport();
}

}

}
//This is a .dll
ClassB
{

void CClassB::StartThread()
{
_beginthread(MYBThread, 0, LPVOID(this));
}

void MYBThread(void* pVoid)
{
CClassB* pPointer = static_cast<cclassb*>(pVoid);
while (pPointer->IsOn()) //HERE IS WHERE THE APP Freezes
{
//do something

}
_endthread();

}

}

ClassC
{

CClassB* m_arrPtr[3];

}

Rajkumar R15-Mar-08 18:59

Rajkumar R

15-Mar-08 18:59

LCI wrote:
pApp->arrPtr[i]->StartThread();

are you correctly assigning the Object for arrPtr[i]? as far you are not dereferencing the this pointer you can call a member function with invalid pointer.
void CClassB::StartThread()
{
_beginthread(MYBThread, 0, LPVOID(this));
}
in startThread function you are only passing the this pointer which is not deferenced, possibly IsOn is using the this pointer crashes the application.

LCI17-Mar-08 2:09

17-Mar-08 2:09

I sort of see what you are saying. Can you expand a little?

Thanks,

Rajkumar R17-Mar-08 4:17

Rajkumar R

17-Mar-08 4:17

are you sure arrPtr[i] contains valid object? debug it or show the code that fills the array.

LCI17-Mar-08 4:30

Identify 32 bit binary or 64 bit binary

17-Mar-08 4:30

I will check.
In my code i use it to make another function call in class B and all is well. However, the call in questiuon here is actually used within an "if" block. Scope should be ok though. I will check on it.

tingu13-Mar-08 9:03

tingu

13-Mar-08 9:03

I am looking for a C++ function which can identify the architecture of an executable file (binary) e.g. whether it is a 32 bit or 64 bit. I heard such a function might be available in imagehlp.dll

Can somebody help?

led mike13-Mar-08 9:15

13-Mar-08 9:15

harsha1305 wrote:
I heard such a function might be available in imagehlp.dll

Excellent! Please post back what you find after reading the imagehlp documentation

ThatsAlok13-Mar-08 19:56

ThatsAlok

13-Mar-08 19:56

led mike wrote:
Excellent! Please post back what you find after reading the imagehlp documentation

he he he.. please let me know also... any way some voted you down, let me average it down!

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow
Never mind - my own stupidity is the source of every "problem" - Mixture

cheers,
Alok Gupta
VC Forum Q&A :- I/IV
Support CRY- Child Relief and You/codeProject$$>

led mike14-Mar-08 6:44

14-Mar-08 6:44

Like I care if monkeys on this site vote me down. I can still read documentation and develop my own software, monkey votes will never change that.

Mark Salsbery13-Mar-08 9:16

Mark Salsbery

13-Mar-08 9:16

In imagehlp, maybe MapAndLoad()[^]
and LOADED_IMAGE.FileHeader.Machine.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

led mike13-Mar-08 10:21

13-Mar-08 10:21

Just curious, what did you find attractive about that bait? Big Grin | :-D

Re: Identify 32 bit binary or 64 bit binary [modified]

Mark Salsbery13-Mar-08 10:39

Mark Salsbery

13-Mar-08 10:39

Its wigglyness?

I was going to say "Someone has to do their research for them" until I saw the post below...

Apparently, somebody has to write the code for them Smile | :)

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Randor 13-Mar-08 10:25

Randor

13-Mar-08 10:25

Im feeling generous today. I created a function for you.

DWORD GetPEMachineType(LPTSTR sz)
{
	HANDLE hFile = CreateFile(sz,GENERIC_WRITE | GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE,NULL,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,NULL);
	if(NULL != hFile)
	{
		LARGE_INTEGER bigInt;
		BOOL diditWork = GetFileSizeEx(hFile, &bigInt);
		HANDLE hFileMap = CreateFileMapping(hFile,NULL,PAGE_READWRITE,bigInt.HighPart,bigInt.LowPart + 0x2000 ,_T("someGUID"));
		if(NULL != hFileMap)
		{
			LPVOID hMap = MapViewOfFile(hFileMap,FILE_MAP_READ,0,0,0);
			if(NULL != hMap)
			{
				HMODULE hModule = (HMODULE)hMap;
				IMAGE_DOS_HEADER * pDosHeader = (IMAGE_DOS_HEADER *)hModule;
				IMAGE_FILE_HEADER * pFileHeader = (IMAGE_FILE_HEADER *)(((LPBYTE)hModule) + pDosHeader->e_lfanew + sizeof(IMAGE_NT_SIGNATURE));
				return pFileHeader->Machine;
			}
		}
	}
}

Here is a link to the current PE format specification:

http://www.microsoft.com/whdc/system/platform/firmware/PECOFF.mspx[^]

The possibilities include:

IMAGE_FILE_MACHINE_UNKNOWN 0x0 The contents of this field are assumed to be applicable to any machine type
IMAGE_FILE_MACHINE_AM33 0x1d3 Matsushita AM33
IMAGE_FILE_MACHINE_AMD64 0x8664 x64
IMAGE_FILE_MACHINE_ARM 0x1c0 ARM little endian
IMAGE_FILE_MACHINE_EBC 0xebc EFI byte code
IMAGE_FILE_MACHINE_I386 0x14c Intel 386 or later processors and compatible processors
IMAGE_FILE_MACHINE_IA64 0x200 Intel Itanium processor family
IMAGE_FILE_MACHINE_M32R 0x9041 Mitsubishi M32R little endian
IMAGE_FILE_MACHINE_MIPS16 0x266 MIPS16
IMAGE_FILE_MACHINE_MIPSFPU 0x366 MIPS with FPU
IMAGE_FILE_MACHINE_MIPSFPU16 0x466 MIPS16 with FPU
IMAGE_FILE_MACHINE_POWERPC 0x1f0 Power PC little endian
IMAGE_FILE_MACHINE_POWERPCFP 0x1f1 Power PC with floating point support
IMAGE_FILE_MACHINE_R4000 0x166 MIPS little endian
IMAGE_FILE_MACHINE_SH3 0x1a2 Hitachi SH3
IMAGE_FILE_MACHINE_SH3DSP 0x1a3 Hitachi SH3 DSP
IMAGE_FILE_MACHINE_SH4 0x1a6 Hitachi SH4
IMAGE_FILE_MACHINE_SH5 0x1a8 Hitachi SH5
IMAGE_FILE_MACHINE_THUMB 0x1c2 Thumb
IMAGE_FILE_MACHINE_WCEMIPSV2 0x169 MIPS little-endian WCE v2

Best Wishes,
-David Delaune

modified on Thursday, March 13, 2008 4:32 PM

led mike13-Mar-08 10:33

13-Mar-08 10:33

Randor wrote:
Im feeling generous today. I created a function for you.

Now all you have to do is hope you never have to work with him since you may have just helped him stay employed in the industry.

Randor 13-Mar-08 10:38

Randor

13-Mar-08 10:38

Look on the bright side, thats one less homeless person to worry about.

-David Delaune