man/pthread_key_create.3

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  33 .Dd April 4, 1996
  34 .Dt PTHREAD_KEY_CREATE 3
  35 .Os
  36 .Sh NAME
  37 .Nm pthread_key_create
  38 .Nd thread-specific data key creation
  39 .Sh SYNOPSIS
  40 .In pthread.h
  41 .Ft int
  42 .Fn pthread_key_create "pthread_key_t *key" "void (*destructor)(void *)"
  43 .Sh DESCRIPTION
  44 The
  45 .Fn pthread_key_create
  46 function creates a thread-specific data key visible to all threads in the
  47 process.
  48 Key values provided by
  49 .Fn pthread_key_create
  50 are opaque objects used to locate thread-specific data.
  51 Although the same
  52 key value may be used by different threads, the values bound to the key
  53 by
  54 .Fn pthread_setspecific
  55 are maintained on a per-thread basis and persist for the life of the calling
  56 thread.
  57 .Pp
  58 Upon key creation, the value NULL is associated with the new key in all
  59 active threads.
  60 Upon thread creation, the value NULL is associated with all
  61 defined keys in the new thread.
  62 .Pp
  63 An optional destructor function may be associated with each key value.
  64 At
  65 thread exit, if a key value has a non-NULL destructor pointer, and the
  66 thread has a non-NULL value associated with the key, the function pointed
  67 to is called with the current associated value as its sole argument.
  68 The
  69 order of destructor calls is unspecified if more than one destructor exists
  70 for a thread when it exits.
  71 .Pp
  72 If, after all the destructors have been called for all non-NULL values
  73 with associated destructors, there are still some non-NULL values with
  74 associated destructors, then the process is repeated.
  75 If, after at least
  76 [PTHREAD_DESTRUCTOR_ITERATIONS] iterations of destructor calls for
  77 outstanding non-NULL values, there are still some non-NULL values with
  78 associated destructors, the implementation stops calling destructors.
  79 .Sh RETURN VALUES
  80 If successful, the
  81 .Fn pthread_key_create
  82 function will store the newly created key value at the location specified by
  83 .Fa key
  84 and returns zero.
  85 Otherwise an error number will be returned to indicate
  86 the error.
  87 .Sh ERRORS
  88 The
  89 .Fn pthread_key_create
  90 function will fail if:
  91 .Bl -tag -width Er
  92 .It Bq Er EAGAIN
  93 The system lacked the necessary resources to create another thread-specific
  94 data key, or the system-imposed limit on the total number of keys per process
  95 [PTHREAD_KEYS_MAX] would be exceeded.
  96 .It Bq Er ENOMEM
  97 Insufficient memory exists to create the key.
  98 .El
  99 .Sh SEE ALSO
 100 .Xr pthread_getspecific 3 ,
 101 .Xr pthread_key_delete 3 ,
 102 .Xr pthread_setspecific 3
 103 .Sh STANDARDS
 104 The
 105 .Fn pthread_key_create
 106 function conforms to
 107 .St -p1003.1-96 .