valgrind memory leak errors when using pthread_create

Question

I\'m writing a program using the pthread library. When I run my program with the command valgrind --leak-check=full, I get the following errors description:

Answer 1

Please note that the default pthread_create behavior is "joinable" NOT DETACHED. Therefore some OS resources would still remain in the process after pthread finished, which would result in zombie pthread and leads to increased VIRTUAL/resident memory usage.

The four solution @sehe mentioned would fix this problem.

However if you thread is a long-standing one, this might not be really needed. for example, if the pthread lives through the whole life of the process.

Answer 2

when not working with joinable threads the exiting thread needs to call pthread_detach(pthread_self()) in order to release all its resources.

Answer 3

A thread's resources are not immediately released at termination, unless the thread was created with the detach state attribute set to PTHREAD_CREATE_DETACHED, or if pthread_detach is called for its pthread_t.

An undetached thread will remain terminated state until its identifier is passed to pthread_join or pthread_detach.

To sum it up, you have three options:

1. create your thread with detached attribute set(PTHREAD_CREATE_DETACHED attribute)
2. Detach your thread after creation (by calling pthread_detach), or
3. Join with the terminated threads to recycle them (by calling pthread_join).

Hth.

Answer 4

In addition to the correct answers given you by other users, I suggest you to read this:

Tracking down a memory leak in multithreaded C application

Answer 5

You can make the thread in detached state to avoid the memory leak if the thread should not be joined (or just expires on it's own).

To explicitly create a thread as joinable or detached, the attr argument in the pthread_create() routine is used. The typical 4 step process is:

• Declare a pthread attribute variable of the pthread_attr_t data type
• Initialize the attribute variable with pthread_attr_init()
• Set the attribute detached status with pthread_attr_setdetachstate()
• When done, free library resources used by the attribute with pthread_attr_destroy()