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-.TH PTHREAD_ATTR_SETGUARDSIZE 3 2014-05-28 "Linux" "Linux Programmer's Manual"
-.SH NAME
-pthread_attr_setguardsize, pthread_attr_getguardsize \- set/get guard size
-attribute in thread attributes object
-.SH SYNOPSIS
-.nf
-.B #include <pthread.h>
-
-.BI "int pthread_attr_setguardsize(pthread_attr_t *" attr \
-", size_t " guardsize );
-.BI "int pthread_attr_getguardsize(const pthread_attr_t *" attr \
-", size_t *" guardsize );
-.sp
-Compile and link with \fI\-pthread\fP.
-.fi
-.SH DESCRIPTION
-The
-.BR pthread_attr_setguardsize ()
-function sets the guard size attribute of the
-thread attributes object referred to by
-.I attr
-to the value specified in
-.IR guardsize .
-
-If
-.I guardsize
-is greater than 0,
-then for each new thread created using
-.I attr
-the system allocates an additional region of at least
-.I guardsize
-bytes at the end of the thread's stack to act as the guard area
-for the stack (but see BUGS).
-
-If
-.I guardsize
-is 0, then new threads created with
-.I attr
-will not have a guard area.
-
-The default guard size is the same as the system page size.
-
-If the stack address attribute has been set in
-.I attr
-(using
-.BR pthread_attr_setstack (3)
-or
-.BR pthread_attr_setstackaddr (3)),
-meaning that the caller is allocating the thread's stack,
-then the guard size attribute is ignored
-(i.e., no guard area is created by the system):
-it is the application's responsibility to handle stack overflow
-(perhaps by using
-.BR mprotect (2)
-to manually define a guard area at the end of the stack
-that it has allocated).
-
-The
-.BR pthread_attr_getguardsize ()
-function returns the guard size attribute of the
-thread attributes object referred to by
-.I attr
-in the buffer pointed to by
-.IR guardsize .
-.SH RETURN VALUE
-On success, these functions return 0;
-on error, they return a nonzero error number.
-.SH ERRORS
-POSIX.1-2001 documents an
-.B EINVAL
-error if
-.I attr
-or
-.I guardsize
-is invalid.
-On Linux these functions always succeed
-(but portable and future-proof applications should nevertheless
-handle a possible error return).
-.SH VERSIONS
-These functions are provided by glibc since version 2.1.
-.SH ATTRIBUTES
-.SS Multithreading (see pthreads(7))
-The
-.BR pthread_attr_setguardsize ()
-and
-.BR pthread_attr_getguardsize ()
-functions are thread-safe.
-.SH CONFORMING TO
-POSIX.1-2001.
-.SH NOTES
-A guard area consists of virtual memory pages that are protected
-to prevent read and write access.
-If a thread overflows its stack into the guard area,
-then, on most hard architectures, it receives a
-.B SIGSEGV
-signal, thus notifying it of the overflow.
-Guard areas start on page boundaries,
-and the guard size is internally rounded up to
-the system page size when creating a thread.
-(Nevertheless,
-.BR pthread_attr_getguardsize ()
-returns the guard size that was set by
-.BR pthread_attr_setguardsize ().)
-
-Setting a guard size of 0 may be useful to save memory
-in an application that creates many threads
-and knows that stack overflow can never occur.
-
-Choosing a guard size larger than the default size
-may be necessary for detecting stack overflows
-if a thread allocates large data structures on the stack.
-.SH BUGS
-As at glibc 2.8, the NPTL threading implementation includes
-the guard area within the stack size allocation,
-rather than allocating extra space at the end of the stack,
-as POSIX.1 requires.
-(This can result in an
-.B EINVAL
-error from
-.BR pthread_create (3)
-if the guard size value is too large,
-leaving no space for the actual stack.)
-
-The obsolete LinuxThreads implementation did the right thing,
-allocating extra space at the end of the stack for the guard area.
-.\" glibc includes the guardsize within the allocated stack size,
-.\" which looks pretty clearly to be in violation of POSIX.
-.\"
-.\" Filed bug, 22 Oct 2008:
-.\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6973
-.\"
-.\" Older reports:
-.\" https//bugzilla.redhat.com/show_bug.cgi?id=435337
-.\" Reportedly, LinuxThreads did the right thing, allocating
-.\" extra space at the end of the stack:
-.\" http://sourceware.org/ml/libc-alpha/2008-05/msg00086.html
-.SH EXAMPLE
-See
-.BR pthread_getattr_np (3).
-.SH SEE ALSO
-.BR mmap (2),
-.BR mprotect (2),
-.BR pthread_attr_init (3),
-.BR pthread_attr_setstack (3),
-.BR pthread_attr_setstacksize (3),
-.BR pthread_create (3),
-.BR pthreads (7)
-.SH COLOPHON
-This page is part of release 3.79 of the Linux
-.I man-pages
-project.
-A description of the project,
-information about reporting bugs,
-and the latest version of this page,
-can be found at
-\%http://www.kernel.org/doc/man\-pages/.
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