include/bits/unistd_ext.h

   1 /* System-specific extensions of <unistd.h>, Linux version.
   2    Copyright (C) 2019-2021 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _UNISTD_H
  20 # error "Never include <bits/unistd_ext.h> directly; use <unistd.h> instead."
  21 #endif
  22
  23 #ifdef __USE_GNU
  24
  25 /* Return the kernel thread ID (TID) of the current thread.  The
  26    returned value is not subject to caching.  Most Linux system calls
  27    accept a TID in place of a PID.  Using the TID to change properties
  28    of a thread that has been created using pthread_create can lead to
  29    undefined behavior (comparable to manipulating file descriptors
  30    directly that have not been created explicitly).  Note that a TID
  31    uniquely identifies a thread only while this thread is running; a
  32    TID can be reused once a thread has exited, even if the thread is
  33    not detached and has not been joined.  */
  34 extern __pid_t gettid (void) __THROW;
  35
  36 #endif