35.1.1 Return Values
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.