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All Rights Reserved. .\" Copyright (c) 2008, Sun Microsystems, Inc. All Rights Reserved. .\" .TH PTHREAD_RWLOCK_INIT 3C "Dec 11, 2022" .SH NAME pthread_rwlock_init, pthread_rwlock_destroy \- initialize or destroy read-write lock object .SH SYNOPSIS cc -mt [ \fIflag\fR... ] \fIfile\fR... -lpthread [ \fIlibrary\fR... ] #include \fBint\fR \fBpthread_rwlock_init\fR(\fBpthread_rwlock_t *restrict\fR \fIrwlock\fR, \fBconst pthread_rwlockattr_t *restrict\fR \fIattr\fR); .fi .LP .nf \fBint\fR \fBpthread_rwlock_destroy\fR(\fBpthread_rwlock_t *\fR\fIrwlock\fR); .fi .LP .nf \fBpthread_rwlock_t\fR \fIrwlock\fR = \fBPTHREAD_RWLOCK_INITIALIZER\fR; .fi .SH DESCRIPTION The \fBpthread_rwlock_init()\fR function initializes the read-write lock referenced by \fIrwlock\fR with the attributes referenced by \fIattr\fR. If \fIattr\fR is NULL, the default read-write lock attributes are used; the effect is the same as passing the address of a default read-write lock attributes object. Once initialized, the lock can be used any number of times without being re-initialized. Upon successful initialization, the state of the read-write lock becomes initialized and unlocked. Results are undefined if \fBpthread_rwlock_init()\fR is called specifying an already initialized read-write lock. Results are undefined if a read-write lock is used without first being initialized. .sp .LP If the \fBpthread_rwlock_init()\fR function fails, \fIrwlock\fR is not initialized and the contents of \fIrwlock\fR are undefined. .sp .LP The \fBpthread_rwlock_destroy()\fR function destroys the read-write lock object referenced by \fIrwlock\fR and releases any resources used by the lock. The effect of subsequent use of the lock is undefined until the lock is re-initialized by another call to \fBpthread_rwlock_init()\fR. An implementation may cause \fBpthread_rwlock_destroy()\fR to set the object referenced by \fIrwlock\fR to an invalid value. Results are undefined if \fBpthread_rwlock_destroy()\fR is called when any thread holds \fIrwlock\fR. Attempting to destroy an uninitialized read-write lock results in undefined behaviour. A destroyed read-write lock object can be re-initialized using \fBpthread_rwlock_init()\fR; the results of otherwise referencing the read-write lock object after it has been destroyed are undefined. .sp .LP In cases where default read-write lock attributes are appropriate, the macro \fBPTHREAD_RWLOCK_INITIALIZER\fR can be used to initialize read-write locks that are statically allocated. The effect is equivalent to dynamic initialization by a call to \fBpthread_rwlock_init()\fR with the parameter \fIattr\fR specified as NULL, except that no error checks are performed. .SH RETURN VALUES If successful, the \fBpthread_rwlock_init()\fR and \fBpthread_rwlock_destroy()\fR functions return \fB0\fR. Otherwise, an error number is returned to indicate the error. .SH ERRORS The \fBpthread_rwlock_init()\fR and \fBpthread_rwlock_destroy()\fR functions will fail if: .sp .ne 2 .na \fB\fBEINVAL\fR\fR .ad .RS 10n The value specified by \fIattr\fR is invalid. .RE .sp .ne 2 .na \fB\fBEINVAL\fR\fR .ad .RS 10n The value specified by \fIrwlock\fR is invalid. .RE .SH ATTRIBUTES See \fBattributes\fR(7) for descriptions of the following attributes: .sp .sp .TS box; c | c l | l . ATTRIBUTE TYPE ATTRIBUTE VALUE _ Interface Stability Standard _ MT-Level MT-Safe .TE .SH SEE ALSO .BR pthread_rwlock_rdlock (3C), .BR pthread_rwlock_unlock (3C), .BR pthread_rwlock_wrlock (3C), .BR pthread_rwlockattr_init (3C), .BR attributes (7), .BR standards (7)