PTHREAD_MUTEX_INITIALIZER vs pthread_mutex_init ( &mutex, param)

http://stackoverflow.com/questions/14320041/pthread-mutex-initializer-vs-pthread-mutex-init-mutex-param

Is there any difference between

pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;

Or

pthread_mutex_t lock;pthread_mutex_init ( &lock, NULL);

Am I safe enough if I use only the first method ?

NOTE: My question mostly refers to very small programs where at the most what I'll do is connect several clients to a server and resolve their inquiries with worker threads.

42down voteaccepted

By older versions of the POSIX standard the first method with an initializer is only guaranteed to work with statically allocated variables, not when the variable is an auto variable that is defined in a function body. Although I have never seen a platform where this would not be allowed, even for auto variables, and this restriction has been removed in the latest version of the POSIX standard.

The static variant is really preferable if you may, since it allows to write bootstrap code much easier. Whenever at run time you enter into code that uses such a mutex, you can be assured that the mutex is initialized. This is a precious information in multi-threading context.

The method using an init function is preferable when you need special properties for your mutex, such as being recursive e.g or being shareable between processes, not only between threads.

You can set more attributes of the mutex with the dynamic initialisation, plus you can only use the dynamic method if you're adding a bunch of mutexes at run time.

There's nothing wrong with the static approach though, if that fits your needs.

" plus you can only use the dynamic method if you're adding a bunch of mutexes at run time. " 

if your mutex is allocated by malloc() (or belongs to an object that is allocated).
f mutex variable "lock" is part of a structure , then we can not follow 1st approach. we have to use pthread_init(). 

In cases where default mutex attributes are appropriate, the macro PTHREAD_MUTEX_INITIALIZER can be used to initialize mutexes.

If you want to specify attributes for mutex go with dynamic initialization ........

The effect shall be equivalent to dynamic initialization by a call to pthread_mutex_init() with parameter attrspecified as NULL, except that no error checks are performed.