Static initializers in the PTHREAD API

Source code can be found here:

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[ShubhamKumar-idsm]

please do video on shared memory, message passing and virtual memory

[narasarajv]

Thank you.
Can you please suggest me which is the best book for Linux for beginners?

[xofrio]

class Test {
public:
static pthread_mutex_t mutex;
};

pthread_mutex_t Test::mutex ( PTHREAD_MUTEX_INITIALIZER ); - this one works

pthread_mutex_t Test::mutex { PTHREAD_MUTEX_INITIALIZER }; - while this does not, because "cannot convert '<brace-enclosed initializer list>' to 'int"

So when I initialize it like this, I can't use uniform initialization.
But why? Could you explain it to me?

Or should I just forget about brackets when initializing such a thing and simply use "=" until I get old and wise?