pthread_attr_setdetachstate(3T) SDK R4.11 pthread_attr_setdetachstate(3T)
NAME
pthreadattrsetdetachstate, pthreadattrgetdetachstate - manipulate
thread detachstate attribute
SYNOPSIS
#include <pthread.h>
int pthreadattrsetdetachstate(pthreadattrt *attr,
int *detachstate);
int pthreadattrgetdetachstate(pthreadattrt *attr);
where:
attr A pointer to a thread attributes object, which should
have been initialized by a previous call to
pthreadattrinit().
detachstate A pointer to the detachstate attribute, which should have
the value 0 or 1; default attribute value = 0 (not
created as detached)
DESCRIPTION
The detachstate attribute specifies whether or not a thread is
created as detached. If a thread is created as detached, it will
automatically cleanup for itself when it terminates and make its id
available for reuse by the system.
The detachstate attribute is either 0 or 1. A value of 0 causes all
threads created with the attributes object pointed to by attr to be
created as undetached (default). A value of 1 causes all threads
created with the attributes object pointed to by attr to be created
as detached.
Detached threads are not joinable. Under DG/UX, any call to
pthreadjoin() on a detached thread will fail with errno set to
ESRCH. This is similar to the case where an existing thread is
detached with a call to pthreaddetach().
Creating a thread as detached is encouraged when it makes sense for
the thread at hand. It is more efficient to have a thread clean up
after itself than to require a call to pthreadjoin(). A detached
thread can more efficiently perform the cleanup during its exit.
DIAGNOSTICS
Returns
If successful, pthreadattrsetdetachstate() returns 0. Otherwise it
returns -1 and sets errno to indicate the error.
If successful, pthreadattrgetdetachstate() returns 0 or 1,
indicating the detachstate attribute. Otherwise it returns -1 and
sets errno to indicate the error.
Errors
For each of the following conditions, pthreadattrsetdetachstate()
and pthreadattrgetdetachstate() return -1 and set errno to the
corresponding value:
[EINVAL] An invalid attributes object has been specified. This
occurs when DG/UX has detected that the attributes object
pointed to by attr has not been initialized by a previous
call to pthreadattrinit() or has been corrupted.
For each of the following conditions, pthreadattrsetdetachstate()
returns -1 and sets errno to the corresponding value:
[EINVAL] The value pointed to by detachstate is not 0 or 1.
SEE ALSO
pthreadattrinit(3T), pthreadattrdestroy(3T), pthreadcreate(3T),
pthreaddetach(3T), pthreadjoin(3T), pthreadexit(3T).
NOTES
The fact that the detachstate argument to pthreadattrsetdetachstate
is a pointer to the detachstate instead of the detachstate itself
arrises from a typo in Draft 6 of the Posix 1003.4a standard. DG/UX
chose to mimick this mistake in order "conform fully" to Draft 6.
This typo has been corrected in subsequent drafts of the standard.
Other problems have also been corrected in future drafts. These
include using symbolic constants instead of 0 and 1, and returning
the detachstate via an (int *) parameter to pthreadgetdetachstate().
Creating threads as detached is preferrable to the using
pthreaddetach() on an existing thread, as the latter call will not
likely make it into the final standard. Moreover, creating a thread
as detached is more efficient than detaching it after it has been
created.
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