# Thread support library

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< c

If the macro constant `__STDC_NO_THREADS__`(C11) is defined by the compiler, the header `<threads.h>` and all of the names listed here are not provided.

### Threads

Defined in header `<threads.h>`
`thrd_t` | implementation-defined complete object type identifying a thread
thrd_create (C11) | creates a thread (function)
thrd_equal (C11) | checks if two identifiers refer to the same thread (function)
thrd_current (C11) | obtains the current thread identifier (function)
thrd_sleep (C11) | suspends execution of the calling thread for the given period of time (function)
thrd_yield (C11) | yields the current time slice (function)
thrd_exit (C11) | terminates the calling thread (function)
thrd_detach (C11) | detaches a thread (function)
thrd_join (C11) | blocks until a thread terminates (function)
thrd_success thrd_timedout thrd_busy thrd_nomem thrd_error (C11) | indicates a thread error status (constant)
thrd_start_t (C11) | a typedef of the function pointer type int(*)(void*), used by thrd_create (typedef)

### Mutual exclusion

Defined in header `<threads.h>`
`mtx_t` | mutex identifier
mtx_init (C11) | creates a mutex (function)
mtx_lock (C11) | blocks until locks a mutex (function)
mtx_timedlock (C11) | blocks until locks a mutex or times out (function)
mtx_trylock (C11) | locks a mutex or returns without blocking if already locked (function)
mtx_unlock (C11) | unlocks a mutex (function)
mtx_destroy (C11) | destroys a mutex (function)
mtx_plain mtx_recursive mtx_timed (C11)(C11)(C11) | defines the type of a mutex (enum)

##### Call once

call_once (C11) | calls a function exactly once (function)

### Condition variables

Defined in header `<threads.h>`
`cnd_t` | condition variable identifier
cnd_init (C11) | creates a condition variable (function)
cnd_signal (C11) | unblocks one thread blocked on a condition variable (function)
cnd_broadcast (C11) | unblocks all threads blocked on a condition variable (function)
cnd_wait (C11) | blocks on a condition variable (function)
cnd_timedwait (C11) | blocks on a condition variable, with a timeout (function)
cnd_destroy (C11) | destroys a condition variable (function)

### Thread-local storage

Defined in header `<threads.h>`
thread_local (C11) | thread local type macro (macro constant)
`tss_t` | thread-specific storage pointer
TSS_DTOR_ITERATIONS (C11) | maximum number of times destructors are called (macro constant)
`tss_dtor_t` | function pointer type void(*)(void*), used for TSS destructor
tss_create (C11) | creates thread-specific storage pointer with a given destructor (function)
tss_get (C11) | reads from thread-specific storage (function)
tss_set (C11) | write to thread-specific storage (function)
tss_delete (C11) | releases the resources held by a given thread-specific pointer (function)

### Reserved identifiers

Function names, type names, and enumeration constants that begin with either `cnd_`, `mtx_`, `thrd_`, or `tss_`, and a lowercase letter may be added to the declarations in the `<threads.h>` header in future revisions of the C standard, and portable programs should not use those identifiers.

### References

- C11 standard (ISO/IEC 9899:2011):

  - 7.26 Threads <threads.h> (p: 376-387)

  - 7.31.15 Threads <threads.h> (p: 456)

### See also

C++ documentation for Thread support library

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