PTHREAD_KEY_CREATE(3) | Library Functions Manual | PTHREAD_KEY_CREATE(3) |
pthread_key_create
,
pthread_key_delete
—
#include <pthread.h>
int
pthread_key_create
(pthread_key_t
*key, void
(*destructor)(void *));
int
pthread_key_delete
(pthread_key_t
key);
pthread_key_create
() function creates a
thread-specific data key visible to all threads in the process. Key values are
opaque objects used to locate thread-specific data. The same key value may be
used by different threads, but the values bound to the key by
pthread_setspecific
() are maintained on a per-thread
basis and persist for the life of the calling thread.
Upon key creation, the value NULL
is
associated with the new key in all active threads. Upon thread creation, the
value NULL
is associated with all defined keys in
the new thread.
An optional destructor function may be associated with each key
value. At thread exit, if a key value has a non-NULL
destructor pointer, and the thread has a non-NULL
value associated with the key, the function pointed to is called with the
current associated value as its sole argument. The order of destructor calls
is unspecified if more than one destructor exists for a thread when it
exits.
If, after all the destructors have been called for all
non-NULL
values with associated destructors, there
are still some non-NULL
values with associated
destructors, then the process is repeated. If, after at least
PTHREAD_DESTRUCTOR_ITERATIONS
iterations of
destructor calls for outstanding non-NULL
values,
there are still some non-NULL
values with associated
destructors, the implementation stops calling destructors.
The pthread_key_delete
() function deletes
a thread-specific data key previously returned by
pthread_key_create
(). The thread-specific data
values associated with key need not be
NULL
at the time of the call. It is the
responsibility of the application to free any application storage or perform
any cleanup actions for data structures related to the deleted key or
associated thread-specific data in any threads; this cleanup can be done
either before or after pthread_key_delete
() is
called. Any attempt to use key following the call to
pthread_key_delete
() results in undefined
behavior.
The pthread_key_delete
() function itself
is callable from within destructor functions, but destructor functions are
not invoked by the function. Any destructor function that may have been
associated with key will no longer be called upon
thread exit.
pthread_key_create
() function will
store the newly created key value at the location specified by
key and returns zero. Also
pthread_key_delete
() will return zero upon success.
Upon failure both functions return an error number to indicate the cause.
PTHREAD_KEYS_MAX
_POSIX_THREAD_KEYS_MAX
.pthread_key_create
() may fail if:
EAGAIN
]PTHREAD_KEYS_MAX
would be
exceeded.ENOMEM
]The pthread_key_delete
() function may fail
if:
EINVAL
]May 29, 2015 | NetBSD 9.2 |