threading question

[luvcloud]

i read that C++ do not really have support for thread. Instead the API of the operating system is used. does this code below making an Win32 API call? the header imports process.h.

_beginthread(AcceptProc,0,&sockListen);

 

[MKuiper]

Do not use the API CreateThread, because it may cause memoryleaks in VC++. Instead, compile with one of the options /MT, /MTd, MD or /MDd. If you use one of these options, _beginthread or _beginthreadex is recognized.

Marcel

 

[luvcloud]

is there a difference between _beginthread, and the Worker/UI Thread provided in MFC?

 

[MKuiper]

Yes and no.
Yes: _beginthread is controlled by you, you can start anything as a thread.
No: both are threads within the same process.
Question is not quite clear.

Marcel

 

[luvcloud]

Actually what i don't understand is why C++ is said to have no support for threads, when there are a method to create thread which is the _beginthread. i'm trying to understand the way C++ handles multithreading as i need to compare it with C# for my college research project. I understand that most of the time, C++ is just making API calls or it uses class libraries (like MFC) that are wrapper around the API. so is _beginthread an API call too?

 

[MKuiper]

CreateThread is an API, which can be called from within any C-program, regardless of the compiler options.
_beginthread and _beginthreadex are C-runtime functions, which are normally not supported, only if you use one of the compiler options i mentioned in an earlier post. The reason for this is the synchronisation required in a multi-threaded environment.
Suppose two threads are running in the same process. The first thread is executing printf ( "aaaaaaaaaa" ); and the second printf ( "bbbbbbbbbb" ). If there is no synchronization, you might find something like "aaabbbbbbaaaaaaabbbb" in your output. Synchronized, the output will be "aaaaaaaaaabbbbbbbbbb" or "bbbbbbbbbbaaaaaaaaaa".

Marcel
Marcel

 

[eemah]

How can I run a class member method in a thread, in a win 32 console application?

Thanks,
Alberto H.

 

[Zyrenthian]

I would suggest a method pointer that you pass to the thread. See this quick example on method pointers. Cut and paste of the code should be fine

===========================================================================================

#include <iostream.h>

class c1{
public:
	c1::c1(){}
	void sample1();
	void sample2();
	void sample3();
	void sample4();
	void sample5();
	void sample6();

};

void c1::sample1(){cout<<&quot;sample1\n&quot;;}
void c1::sample2(){cout<<&quot;sample2\n&quot;;}
void c1::sample3(){cout<<&quot;sample3\n&quot;;}
void c1::sample4(){cout<<&quot;sample4\n&quot;;}
void c1::sample5(){cout<<&quot;sample5\n&quot;;}
void c1::sample6(){cout<<&quot;sample6\n&quot;;}

class c2{
public:
	c2::c2( void(c1::*ptr)() ):method_ptr(ptr){};
	void setmethod(void(c1::*ptr)());
	void fire();
private:

	void (c1::*method_ptr)();  
};


class c3{
public:
	c3::c3():method_ptr(fxna){};
	void setmethod(int x);
	void fxna(){cout<<&quot;fxna\n&quot;;}
	void fxnb(){cout<<&quot;fxnb\n&quot;;}
	void fxnc(){cout<<&quot;fxnc\n&quot;;}
private:

	void (c3::*method_ptr)();  
};

void c2::fire(){c1 temp;(temp.*method_ptr)();}
void c2::setmethod(void(c1::*ptr)()){method_ptr=ptr;}
void c3::setmethod(int x){
	switch(x)
	{ 
	case 1:method_ptr = fxna;break;
	case 2:method_ptr = fxnb;break;
	case 3:
	default:method_ptr = fxnc;break;
	}
}


int main()
{
	c2 mc2(&c1::sample1);

	mc2.fire();
	mc2.setmethod(&c1::sample2);
	mc2.fire();
	mc2.setmethod(&c1::sample3);
	mc2.fire();
	mc2.setmethod(&c1::sample4);
	mc2.fire();
	mc2.setmethod(&c1::sample5);
	mc2.fire();
	mc2.setmethod(&c1::sample6);
	mc2.fire();

	c3 mc3;

	cout<<&quot;\n\n\n\nbeginning\n\n\n\n&quot;;
	mc3.setmethod(1);
	mc3.setmethod(2);
	mc3.setmethod(3);



	return 0;
}