TSS(3C) Standard C Library Functions TSS(3C)

NAME


tss, tss_create, tss_delete, tss_get, tss_set - thread-specific storage

SYNOPSIS


#include <threads.h>

typedef void (*tss_dtor_t)(void *);

int
tss_create(tss_t *key, tss_dtor_t dtor);

void
tss_delete(tss_t key);

void *
tss_get(tss_t key);

int
tss_set(tss_t key, void *val);

DESCRIPTION


The tss family of functions create, get, set, and destroy thread-specific
storage.

Creating and Destroying Thread-Specific Storage
The tss_create() function creates a new thread-specific data key. The key
space is opaque and global to all threads in the process. Each thread has
its own value-space which can be manipulated with the tss_get() and
tss_set() functions. A given key persists until tss_delete() is called.

When a key is created, the value NULL is associated with all current
threads. When a thread is created, the value NULL is assigned as the value
for the entire key-space.

A key may optionally be created with a destructor function dtor. The
function dtor will run when the thread exits (see thrd_exit(3C)) if the
value for the key is not NULL. The key space's destructors may be run in
any order. When the destructor is run due to a thread exiting, all signals
will be blocked.

The tss_delete() function deletes the key identified by key from the global
name-space. When a key is deleted, no registered destructor is called, it
is up to the calling program to free any storage that was associated with
key across all threads. Because of this property, it is legal to call
tss_delete() from inside a destructor. Any destructors that had been
associated with key will no longer be called when a thread terminates.

Obtaining Values


The tss_get() function may be used to obtain the value associated with key
for the calling thread. Note that if the calling thread has never set a
value, then it will receive the default value, NULL. tss_get() may be
called from a tss destructor.

Setting Values


The tss_set() function sets the value of the key key for the calling thread
to value, which may be obtained by subsequent calls to tss_get. To remove
a value for a specific thread, one may pass NULL in as value. Changing the
value of a key with tss_set() does not cause any destructors to be invoked.
This means that tss_set() may be used in the context of a destructor, but
special care must be taken to avoid leaking storage or causing an infinite
loop.

RETURN VALUES


Upon successful completion, the tss_create() and tss_set() functions return
thrd_success. Otherwise, they return thrd_error to indicate that an error
occurred.

Upon successful completion, the tss_get() function returns the thread-
specific value associated with the given key. If no thread-specific value
is associated with the key or an invalid key was passed in, then NULL is
returned.

INTERFACE STABILITY


Standard

MT-LEVEL
MT-Safe

SEE ALSO


pthread_getspecific(3C), pthread_key_create(3C), pthread_key_delete(3C),
pthread_setspecific(3C), attributes(7)

illumos November 8, 2020 illumos