The function int pthread_cond_init(pthread_cond_t *restrict cond, const pthread_condattr_t *restrict attr); shall initialize the condition variable referenced by cond with attributes referenced by attr.If attr is NULL, the default condition variable attributes shall be used; the effect is the same as passing the address of a default condition variable attributes object. Upon successful initialization, the state of the condition variable shall become initialized. In cases where default condition variable attributes are appropriate, the macro PTHREAD_COND_INITIALIZER can be used to initialize condition variables that are statically allocated. The effect shall be equivalent to dynamic initialization by a call to pthread_cond_init() with parameter attr specified as NULL, except that no error checks are performed. If successful, the pthread_cond_init() function shall return zero; The pthread_cond_init() function shall fail if: [EAGAIN] The system lacked the necessary resources (other than memory) to initialize another condition variable. [ENOMEM] Insufficient memory exists to initialize the condition variable. The pthread_cond_init() function may fail if: [EBUSY] The implementation has detected an attempt to reinitialize the object referenced by cond, a previously initialized, but not yet destroyed, condition variable. [EINVAL] The value specified by attr is invalid. The function shall not return an error code of [EINTR].