Programming Forums > Application Development > C++

myName · Mar 14th, 2006, 1:59 AM

void Processfile()
{
	char FileName[] = "C:\\abc.txt";

	while( true)
	{
		if (fexists(FileName))
		{
			printf("File Exist\n\n");

			ifstream infile("C:\\abc.txt");
			string sLine = "";
			while( getline(infile, sLine) )
			{
				if( strlen(sLine.c_str()))
				{
					printf( "%s\n", sLine.c_str());
				}
			}

			DeleteFile();
		}
		else
		{
			printf( "Not Exist\n\n" );
		}

	}
}

This function, i need to create it as a thread...

I do this

(Toggle Plain Text)

             DWORD   d_threadID = 0;
	CreateThread(NULL,
		0,
		Processfile,
		NULL,
		0,
		(LPDWORD)&d_threadID);

Error

Quote:

error C2664: 'CreateThread' : cannot convert parameter 3 from 'void (void)' to 'unsigned long (__stdcall *)(void *)'
None of the functions with this name in scope match the target type

:o

grumpy · Mar 14th, 2006, 2:26 AM

The error message is fairly self explanatory. The third argument of CreateThread is a pointer to a function that accepts one argument of type void * and returns an unsigned long. The compiler is complaining because you have attempted to pass it a function that accepts no arguments and returns void.

myName · Mar 14th, 2006, 3:03 AM

still can not understand..... please guide...

Cache · Mar 14th, 2006, 3:13 AM

I guess this is Win32 API?

You need to use a specific prototype/calling convention for your thread procedure.

(Toggle Plain Text)

DWORD WINAPI ThreadProc( LPVOID pVoid )

myName · Mar 14th, 2006, 4:02 AM

ok.. i add (LPTHREAD_START_ROUTINE) for the 3th parameter...

(Toggle Plain Text)

              DWORD   d_threadID = 0;
	CreateThread(NULL,
		0,
		(LPTHREAD_START_ROUTINE)Processfile,
		NULL,
		0,
		(LPDWORD)&d_threadID);

Now there is no error..
BUTTTT... :o

Why the process file did not run?
What's wrong????
Anybody see what wrong? please inform.. your help will be very much appreciate...

(Toggle Plain Text)

void Processfile()
{
	char FileName[] = "C:\\abc.txt";

	while( true)
	{
		if (fexists(FileName))
		{
			printf("File Exist\n\n");

			ifstream infile("C:\\abc.txt");
			string sLine = "";
			while( getline(infile, sLine) )
			{
				if( strlen(sLine.c_str()))
				{
					printf( "%s\n", sLine.c_str());
				}
			}

			DeleteFile();
		}
		else
		{
			printf( "Not Exist\n\n" );
		}
                Sleep(200);

          }
}

grumpy · Mar 14th, 2006, 5:32 AM

Sigh. As I said earlier, your function ProcessFile() takes no arguments and returns void. It needs to accept a void pointer and return an unsigned long.

(Toggle Plain Text)

unsigned long ProcessFile(void *)
{
     // the body of your function
}

Using a cast, as in

(Toggle Plain Text)

CreateThread(NULL,
		0,
		(LPTHREAD_START_ROUTINE)Processfile,
		NULL,
		0,
		(LPDWORD)&d_threadID);

tells the compiler not to complain when you pass your version of ProcessFile() as the third argument to CreateThread(). It does not magically allow CreateThread() to work correctly when it (or the thread it creates) attempts to execute your function by passing an argument to it and checking the return value. In fact, using the cast in this instance (passing a function to CreateThread() that is of a different from from what CreateThread() expects) is a good way to ensure your program does not work correctly.

In this case it would also be a good idea to eliminate the (LPDWORD) cast as well from your call. Telling the compiler that &d_threadID is a pointer to a DWORD does not magically turn d_threadID into a DWORD.

Mar 14th, 2006, 3:13 AM	#4
Cache Hobbyist Join Date: Sep 2005 Posts: 261 Rep Power: 4	I guess this is Win32 API? You need to use a specific prototype/calling convention for your thread procedure. (Toggle Plain Text) DWORD WINAPI ThreadProc( LPVOID pVoid ) DWORD WINAPI ThreadProc( LPVOID pVoid )

Mar 14th, 2006, 4:02 AM	#5
myName Programmer Join Date: Oct 2005 Posts: 48 Rep Power: 0	ok.. i add (LPTHREAD_START_ROUTINE) for the 3th parameter... (Toggle Plain Text) DWORD d_threadID = 0; CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)Processfile, NULL, 0, (LPDWORD)&d_threadID); DWORD d_threadID = 0; CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)Processfile, NULL, 0, (LPDWORD)&d_threadID); Now there is no error.. BUTTTT... :o Why the process file did not run? What's wrong???? Anybody see what wrong? please inform.. your help will be very much appreciate... (Toggle Plain Text) void Processfile() { char FileName[] = "C:\\abc.txt"; while( true) { if (fexists(FileName)) { printf("File Exist\n\n"); ifstream infile("C:\\abc.txt"); string sLine = ""; while( getline(infile, sLine) ) { if( strlen(sLine.c_str())) { printf( "%s\n", sLine.c_str()); } } DeleteFile(); } else { printf( "Not Exist\n\n" ); } Sleep(200); } } void Processfile() { char FileName[] = "C:\\abc.txt"; while( true) { if (fexists(FileName)) { printf("File Exist\n\n"); ifstream infile("C:\\abc.txt"); string sLine = ""; while( getline(infile, sLine) ) { if( strlen(sLine.c_str())) { printf( "%s\n", sLine.c_str()); } } DeleteFile(); } else { printf( "Not Exist\n\n" ); } Sleep(200); } }

Mar 14th, 2006, 5:32 AM	#6
grumpy Programming Guru Join Date: Jun 2005 Location: Adelaide, South Australia Posts: 1,224 Rep Power: 5	Sigh. As I said earlier, your function ProcessFile() takes no arguments and returns void. It needs to accept a void pointer and return an unsigned long. (Toggle Plain Text) unsigned long ProcessFile(void ) { // the body of your function } unsigned long ProcessFile(void ) { // the body of your function } Using a cast, as in (Toggle Plain Text) CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)Processfile, NULL, 0, (LPDWORD)&d_threadID); CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)Processfile, NULL, 0, (LPDWORD)&d_threadID); tells the compiler not to complain when you pass your version of ProcessFile() as the third argument to CreateThread(). It does not magically allow CreateThread() to work correctly when it (or the thread it creates) attempts to execute your function by passing an argument to it and checking the return value. In fact, using the cast in this instance (passing a function to CreateThread() that is of a different from from what CreateThread() expects) is a good way to ensure your program does not work correctly. In this case it would also be a good idea to eliminate the (LPDWORD) cast as well from your call. Telling the compiler that &d_threadID is a pointer to a DWORD does not magically turn d_threadID into a DWORD. Last edited by grumpy; Mar 14th, 2006 at 5:50 AM.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Mar 14th, 2006, 2:26 AM	#2
grumpy Programming Guru Join Date: Jun 2005 Location: Adelaide, South Australia Posts: 1,224 Rep Power: 5	The error message is fairly self explanatory. The third argument of CreateThread is a pointer to a function that accepts one argument of type void * and returns an unsigned long. The compiler is complaining because you have attempted to pass it a function that accepts no arguments and returns void.

Mar 14th, 2006, 3:03 AM	#3
myName Programmer Join Date: Oct 2005 Posts: 48 Rep Power: 0	still can not understand..... please guide...

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Programming Forums > Application Development > C++

Thread in C++