thr_setspecific(3C) binds value to the thread-specific data key, key, for the calling thread. For POSIX threads, see pthread_setspecific Syntax.
#include <thread.h> int thr_setspecific(thread_key_t key, void *value);
thr_setspecific() returns 0 if successful. When any of the following conditions is detected, thr_setspecific() fails and returns the corresponding value.
ENOMEM
Description: Insufficient memory is available to associate value with keyp.
EINVAL
Description: keyp is invalid.