What are gcc on linux's equivalent to microsoft's critical sections?

Question

The Microsoft Visual C++ compilers have the EnterCriticalSection and ExitCriticalSection objects to allow for synchronization between threads.

What is the GCC equivalent?

I see references around to __sync_synchronize along with __scoped_lock

In fact I see mention of a number of atomic __sync functions along with a number of __atomic ones.

I actually have been using __sync_fetch_and_add for my atomic increment Should I be using __atomic_add_dispatch instead?
What's the difference?

Which ones should I be using? Are there some constructs in C++ that I can use in both the latest version of GCC and Visual C++ 2010 that are available as I'm going to be writing some cross platform code.

I see boost has some functions available, but for various reasons I'm not allowed to use boost under windows.

Answer 1

On Linux (and other Unixen) you need to use PThreads, or Posix Threads. There is no equivalent to Critical Sections on Windows; use a Mutex instead.

EDIT: See first comment below -- apparently Posix Mutexes are the same as Win32 Critical Sections in that they are bound to a single process.

Answer 2

Check here: http://en.wikipedia.org/wiki/Critical_section

/* Sample C/C++, Unix/Linux */
#include <pthread.h>

/* This is the critical section object (statically allocated). */
static pthread_mutex_t cs_mutex =  PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;

void f()
{
    /* Enter the critical section -- other threads are locked out */
    pthread_mutex_lock( &cs_mutex );

    /* Do some thread-safe processing! */

    /*Leave the critical section -- other threads can now pthread_mutex_lock()  */
    pthread_mutex_unlock( &cs_mutex );
}

int main()
{
    f();

    return 0;
}

Answer 3

EnterCriticalSection and the rest of the APIs are Win32 APIs. As far as cross-platform synchronization APIs, I don't think there are any (since you mention you can't use boost). Also, you mentioned cross-platform, does this mean different architectures too (for the gcc part i.e.). I've seen one large implementation where there was a common set of APIs provided which were conditionally compiled to have the native APIs (like fetch_and_add on AIX) or used pthreads the Win32 APIs. I once tried to use posix threads on win32 but ran into a bunch of issues (but that was a very old version). Now YMMV.

Answer 4

If you are developing programs only for Windows platform, I think the best way is using Win32 API. Otherwise you can use Qt C++ libraries (for that purpose Qt Core is enough).

See also: QMutex and QMutexLocker You can also use: QReadWriteLock