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PTHREAD_ATTR_SETGUARDSIZE(3) Linux Programmer's Manual PTHREAD_ATTR_SETGUARDSIZE(3)
pthread_attr_setguardsize, pthread_attr_getguardsize - set/get guard size
attribute in thread attributes object
#include <pthread.h>
int pthread_attr_setguardsize(pthread_attr_t *attr, size_t guardsize);
int pthread_attr_getguardsize(pthread_attr_t *attr, size_t *guardsize);
Compile and link with -pthread.
The pthread_attr_setguardsize() function sets the guard size attribute of the
thread attributes object referred to by attr to the value specified in
guardsize.
If guardsize is greater than 0, then for each new thread created using attr
the system allocates an additional region of at least guardsize bytes at the
end of the thread's stack to act as the guard area for the stack (but see
BUGS).
If guardsize is 0, then new threads created with 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 attr (using
pthread_attr_setstack(3) or 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
mprotect(2) to manually define a guard area at the end of the stack that it
has allocated).
The pthread_attr_getguardsize() function returns the guard size attribute of
the thread attributes object referred to by attr in the buffer pointed to by
guardsize.
On success, these functions return 0; on error, they return a nonzero error
number.
POSIX.1-2001 documents an EINVAL error if attr or guardsize is invalid. On
Linux these functions always succeed (but portable and future-proof
applications should nevertheless handle a possible error return).
These functions are provided by glibc since version 2.1.
POSIX.1-2001.
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 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, pthread_attr_getguardsize() returns the guard size that was set
by 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.
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 EINVAL error
from 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.
See pthread_getattr_np(3).
mmap(2), mprotect(2), pthread_attr_init(3), pthread_attr_setstack(3),
pthread_attr_setstacksize(3), pthread_create(3), pthreads(7)
This page is part of release 3.32 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
Linux 2008-10-24 PTHREAD_ATTR_SETGUARDSIZE(3)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface