.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH PR_GET_TID_ADDRESS 2const 2025-05-17 "Linux man-pages 6.16"
.SH NAME
PR_GET_TID_ADDRESS
\-
get the clear_child_tid address
.SH LIBRARY
Standard C library
.RI ( libc ,\~ \-lc )
.SH SYNOPSIS
.nf
.BR "#include <linux/prctl.h>" "  /* Definition of " PR_* " constants */"
.B #include <sys/prctl.h>
.P
.BI "int prctl(PR_GET_TID_ADDRESS, int **" addrp );
.fi
.SH DESCRIPTION
Return the
.I clear_child_tid
address set by
.BR set_tid_address (2)
and the
.BR clone (2)
.B CLONE_CHILD_CLEARTID
flag, in the location pointed to by
.IR addrp .
.P
This feature is available only if the kernel is built with the
.B CONFIG_CHECKPOINT_RESTORE
option enabled.
.SH RETURN VALUE
On success,
0 is returned.
On error, \-1 is returned, and
.I errno
is set to indicate the error.
.SH ERRORS
.TP
.B EFAULT
.I addrp
is an invalid address.
.SH STANDARDS
Linux.
.SH HISTORY
Linux 3.5.
.\" commit 300f786b2683f8bb1ec0afb6e1851183a479c86d
.SH CAVEATS
Note that since the
.BR prctl ()
system call does not have a compat implementation for
the AMD64 x32 and MIPS n32 ABIs,
and the kernel writes out a pointer using the kernel's pointer size,
this operation expects a user-space buffer of 8 (not 4) bytes on these ABIs.
.SH SEE ALSO
.BR prctl (2)