Thread: Memory leak on pthread_create?

Memory leak on pthread_create - CodeGuru Forums

If you write a simple, complete program and post it, we'll tell you if it contains any memory leaks - then compare that to what Valgrind says and go from there.

gg

Read the examples here -> https://computing.llnl.gov/tutorials...reatingThreads
main() ends by calling pthread_exit().

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <pthread.h>

void* process( void* data ) {
  printf( "hello world\n" );
}

int main() {
  pthread_t th;
  pthread_attr_t attr;
  pthread_attr_init(&attr);
  pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
  pthread_create( &th, &attr, process, NULL );
  pthread_attr_destroy(&attr);
  //pthread_exit(0);  // no leak when this is in the code.
  // dummy
  return 0;
}

Originally Posted by SterlingM

Whenever I run that code, with or without the explicit pthread_exit, I still get a possible memory loss of 144 bytes each time. So I should just regard that as wrong?

Maybe. When I run that code with pthread_exit(), I get a leak of 272 bytes in one block allocated by pthread_create(). Without pthread_exit(), there is no leak.

But pthread_exit() is pretty vital if you have detached threads and main() ends. Try this one:

Code:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>

void* process( void* data ) {
  printf("%ld hello world\n", (long int)data);
  return NULL;
}

int main() {
	pthread_t th[3];
	long int i;
	for (i = 0; i < 3; i++) {
		pthread_create(&th[i], NULL, process, (void*)i);
		pthread_detach(th[i]);
	}

	pthread_exit(0);
	return 0;
}

I get "All heap blocks were freed -- no leaks are possible" for that with or without pthread_exit (but without pthread_exit not all threads complete). Note that that pthread_exit() terminates main, ie, the return statement is not executed.

Originally Posted by http://cursuri.cs.pub.ro/~apc/2003/resources/pthreads/uguide/users-18.htm#285690

Termination of the initial thread via pthread_exit() or any thread termination mechanism terminates the entire process.

Just returning from main only ends that thread and I believe condemns any incomplete threads spawned in main to some kind of weird oblivion.

It's always possible that there is a bug in your library implementation of pthread, or even a bug in valgrind.

If you demonstrate that you have the problem in a really simple test case (as above), and your main code has no other issues, then I think you should be able to claim success.

BTW, I have
$ valgrind --version
valgrind-3.6.0.SVN-Debian