The Open Group Base Specifications Issue 7
IEEE Std 1003.1-2008, 2016 Edition
Copyright © 2001-2016 The IEEE and The Open Group

#### NAME

> pthread_rwlockattr_destroy, pthread_rwlockattr_init - destroy and initialize the read-write lock attributes object

#### SYNOPSIS

> ``#include <pthread.h>
> int pthread_rwlockattr_destroy(pthread_rwlockattr_t *`attr`);
> int pthread_rwlockattr_init(pthread_rwlockattr_t *`attr`);
> ``

#### DESCRIPTION

> The pthread_rwlockattr_destroy() function shall destroy a read-write lock attributes object. A destroyed attr attributes object can be reinitialized using pthread_rwlockattr_init(); the results of otherwise referencing the object after it has been destroyed are undefined. An implementation may cause pthread_rwlockattr_destroy() to set the object referenced by attr to an invalid value.

> The pthread_rwlockattr_init() function shall initialize a read-write lock attributes object attr with the default value for all of the attributes defined by the implementation.

> Results are undefined if pthread_rwlockattr_init() is called specifying an already initialized attr attributes object.

> After a read-write lock attributes object has been used to initialize one or more read-write locks, any function affecting the attributes object (including destruction) shall not affect any previously initialized read-write locks.

> The behavior is undefined if the value specified by the attr argument to pthread_rwlockattr_destroy() does not refer to an initialized read-write lock attributes object.

#### RETURN VALUE

> If successful, the pthread_rwlockattr_destroy() and pthread_rwlockattr_init() functions shall return zero; otherwise, an error number shall be returned to indicate the error.

#### ERRORS

> The pthread_rwlockattr_init() function shall fail if:

> [ENOMEM]
>   Insufficient memory exists to initialize the read-write lock attributes object.

> These functions shall not return an error code of [EINTR].

The following sections are informative.

#### EXAMPLES

> None.

#### APPLICATION USAGE

> None.

#### RATIONALE

> If an implementation detects that the value specified by the attr argument to pthread_rwlockattr_destroy() does not refer to an initialized read-write lock attributes object, it is recommended that the function should fail and report an [EINVAL] error.

#### FUTURE DIRECTIONS

> None.

#### SEE ALSO

> pthread_rwlock_destroy, pthread_rwlockattr_getpshared

> XBD <pthread.h>

#### CHANGE HISTORY

> First released in Issue 5.

#### Issue 6

> The following changes are made for alignment with IEEE Std 1003.1j-2000:

> - The margin code in the SYNOPSIS is changed to THR to indicate that the functionality is now part of the Threads option (previously it was part of the Read-Write Locks option in IEEE Std 1003.1j-2000 and also part of the XSI extension).

> - The SEE ALSO section is updated.

#### Issue 7

> The pthread_rwlockattr_destroy() and pthread_rwlockattr_init() functions are moved from the Threads option to the Base.

> The [EINVAL] error for an uninitialized read-write lock attributes object is removed; this condition results in undefined behavior.

End of informative text.

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