tss_get(3) - NetBSD Manual Pages

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TSS(3)                  NetBSD Library Functions Manual                 TSS(3)


NAME

     tss -- thread-specific storage functions


LIBRARY

     POSIX Threads Library (libpthread, -lpthread)


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);

     #define TSS_DTOR_ITERATIONS /* implementation specified */


DESCRIPTION

     There are two groups of storage in C programs:

     -   local storage,

     -   global storage.

     Multithreaded programs in C add the third group thread-specific storage.
     This data is private to thread and every entry of this type has an asso-
     ciated tss_t opaque key that is global to all threads in the process.  A
     thread using the tss_t * pointer accesses private data.

     The tss_create() function creates a thread-specific storage with the key
     handler with optional destructor dtor.  If the dtor parameter is not
     NULL, then specified appropriate destructor will be called on thread ter-
     mination.  The destructor is not called if a thread called the
     tss_delete() function for the specified key.  If, after all the destruc-
     tors have been called for all non-NULL values with associated destruc-
     tors, there are still some non-NULL values with associated destructors,
     then the process is repeated.  If, after at least TSS_DTOR_ITERATIONS
     iterations of destructor calls for outstanding non-NULL values, there are
     still some non-NULL values with associated destructors, the NetBSD imple-
     mentation stops calling further destructors.  The thrd_exit(3) function
     must not be called from a destructor.

     The tss_delete() function frees resources used by the thread-specific
     storage identified by the key object.  This function can be called inside
     the dtor destructor, however the destructor is not called by
     tss_delete().

     The tss_get() and tss_set() functions are used to get and set thread-spe-
     cific storage.


RETURN VALUES

     The tss_create() function returns thrd_success on success, otherwise
     thrd_error on failure.

     The tss_delete() function returns no value.

     The tss_get() returns pointer to thread-specific storage on success or
     NULL on failure.

     The tss_set() function returns thrd_success on success, otherwise
     thrd_error on failure.


SEE ALSO

     pthread_getspecific(3), pthread_key_create(3), threads(3)


STANDARDS

     The tss interface conforms to ISO/IEC 9899:2011 (``ISO C11'').


HISTORY

     This interface first appeared in NetBSD 9.


AUTHORS

     Kamil Rytarowski <kamil@NetBSD.org>

NetBSD 11.99                   October 16, 2016                   NetBSD 11.99