Re: checking if the memory was allocted previously

From:

Bart van Ingen Schenau <bart@ingen.ddns.info>

Newsgroups:

comp.lang.c++

Date:

Wed, 9 Jun 2010 01:56:21 -0700 (PDT)

Message-ID:

<265e6113-66f4-470e-b772-7de2079db1b7@x27g2000yqb.googlegroups.com>

On Jun 9, 10:15 am, mjoachimiak <mjoachim...@gmail.com> wrote:

Hi,

I used smth like this (forgive me typos):

//////////////////////////
mystrucure *dynamic_element = NULL

void some_function()
{
if (dynamic_element == NULL)
dynamic_element = malloc(sizeofm(mys=

tructure));

if (dynamic_element != NULL) do_smth(dynamic_element);

}

main()
{
call some_function() many times;
if (dynamic_element != NULL)
free(dynamic_element);}

/////////////////////////////

there is a doc about GMutexhttp://library.gnome.org/devel/glib/unstable/g=

lib-Threads.html#GMutex

that says that this line

if (!mutex) mutex = g_mutex_new ();

can cause race condition.

what about my previous memory allocation ?
Can it cause race condition also?

If some_function can be called from more than one thread, and you
can't guarantee that the memory has been allocated before those
threads are started, then your code also has a race condition, the
same as for the GMutex case.

If your program only has one thread (which is the default), then it is
absolutely impossible to have race conditions.

Bart v Ingen Schenau