not 'free'ing 'malloc'ed memory

Hammo · 03-03-2004, 04:56 AM

i have a question concerning malloc() and free().

i use malloc to allocate some memory in main() then pass the returned pointer to a thread. when an error occures in another thread in the same program i want to terminate the whole program by calling exit() in the error thread to terminate the process immediately.

my question is .... does the unfreed memory allocated in main get deallocated automatically when the process ends or will it remain reserved?

thanks.

cjp · 03-03-2004, 05:01 AM

Memory is a resource that is shared between the threads. I think that it will only be deallocated when all threads have terminated.

You can check this by making a test program that allocates a large memory area, so that you can see in e.g. top what happens

cjcuk · 03-03-2004, 05:04 AM

Quote:

Originally posted by Hammo
i have a question concerning malloc() and free().

i use malloc to allocate some memory in main() then pass the returned pointer to a thread. when an error occures in another thread in the same program i want to terminate the whole program by calling exit() in the error thread to terminate the process immediately.

my question is .... does the unfreed memory allocated in main get deallocated automatically when the process ends or will it remain reserved?

thanks.

If you are referring to process as a thread, then it should not be freed when the thread exits. If you are referring to process as the in-memory version of your program ( meaning, all threads ), then yes it does free at the end of execution -- as all mappings are removed.

Hammo · 03-03-2004, 05:09 AM

with process i mean the process which encapsulates all threads in the program

eshwar_ind · 03-03-2004, 05:30 AM

Hey if a process gets terminated in Linux All the resources that are acquired by that process are reclaimed by system. I thihnk in linux automatic resource reclaimation is there. it applies to file descriptors, semaphores (check for this) etc.
I have a doubt regarding semaphores please check it.

eshwar_ind · 03-03-2004, 05:32 AM

Mr. cjcuk semaphores are also taken back by the system right?

cjcuk · 03-03-2004, 07:08 AM

Quote:

Originally posted by eshwar_ind
Mr. cjcuk semaphores are also taken back by the system right?

A call is invoked that removes the process from the semaphore queue.

eshwar_ind · 03-03-2004, 07:15 AM

yes if its waiting for the semaphore. but i am asking about a process takes a semaphore and is killed before it returns that semaphore. Semaphore value is upadted by the system right?

cjcuk · 03-03-2004, 07:27 AM

Quote:

Originally posted by eshwar_ind
yes if its waiting for the semaphore. but i am asking about a process takes a semaphore and is killed before it returns that semaphore. Semaphore value is upadted by the system right?

It has to, otherwise deadlock would occur any time that a process exited without releasing the semaphore.

eshwar_ind · 03-03-2004, 07:33 AM

yes thank you very much