Re: Handle leak when using pthread mutex with win32 api threads

[Dmitrii Sernii <bogolt@gmail.com>]

> > >        static pthread_mutex_t mutex(PTHREAD_RECURSIVE_MUTEX_INITIALIZER);
> >
> > that line above is not thread safe.  you might initialize the same
> > mutex multiple times.  Not good.
> >
> 
> The handle leak comes about because, in pthreads-win32, pthread_mutex_t
> is only a pointer, and the actual mutex struct is malloced by the
> library, in this case, the first time you call pthread_mutex_lock().
> That is, the library just calls pthread_mutex_init() for you. Also, you
> must always call pthread_mutex_destroy() to clean up, just the same as
> if you had called pthread_mutex_init() yourself.

I've made small corrections in test sample, so now mutex initialised
only once, and i've added pthread_mutex_destroy() function call. But
the problem still remains.
Here is two test applications - one of them uses API threads, and the
other pthreads. Program with pthreads don't have any leaks, while
program with API threads produces lots of them.

//program with handle leaks
#include <pthread.h>
#include <windows.h>
#include <conio.h>

pthread_mutex_t mutex(PTHREAD_RECURSIVE_MUTEX_INITIALIZER);

DWORD WINAPI threadProc(void *param)
{
	pthread_mutex_lock(&mutex);
	pthread_mutex_unlock(&mutex);
	return 0;
}

void main()
{
	const int max_threads = 500;
	DWORD id;
	HANDLE th[max_threads];
	int i;
	for (i=0;i<max_threads;i++)
	th[i]=CreateThread(0,0,threadProc,0,0,&id);

	for (i=0;i<max_threads;i++)
	{
		WaitForSingleObject(th[i],INFINITE);
		CloseHandle(th[i]);
	}
	pthread_mutex_destroy(&mutex);
	getch();
}

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

//program without handle leaks
#include <pthread.h>
#include <windows.h>
#include <conio.h>


pthread_mutex_t mutex(PTHREAD_RECURSIVE_MUTEX_INITIALIZER);

void* threadProc(void *param)
{
	pthread_mutex_lock(&mutex);
	pthread_mutex_unlock(&mutex);
    return 0;
}

void main()
{
	const int max_threads = 500;
	DWORD id;
	pthread_t th[max_threads];
	int i;

	for (i=0;i<max_threads;i++)
			pthread_create(&(th[i]),0,threadProc,(void*)i);

	for (i=0;i<max_threads;i++)
		pthread_join(th[i],(void**)&id);

	pthread_mutex_destroy(&mutex);
	getch();
}

Best regards,
Dmitrii Sernii