The ISO C thread specification provides the following enumeration constants for return values from functions in the API:
thrd_timedout ¶A specified time was reached without acquiring the requested resource, usually a mutex or condition variable.
thrd_success ¶The requested operation succeeded.
thrd_busy ¶The requested operation failed because a requested resource is already in use.
thrd_error ¶The requested operation failed.
thrd_nomem ¶The requested operation failed because it was unable to allocate enough memory.