1PTHREAD_ATTR_GETGUARDSIZE(3PP)OSIX Programmer's ManuPaTlHREAD_ATTR_GETGUARDSIZE(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 pthread_attr_getguardsize, pthread_attr_setguardsize - get and set the
13 thread guardsize attribute
14
16 #include <pthread.h>
17 int pthread_attr_getguardsize(const pthread_attr_t *restrict attr,
19 size_t *restrict guardsize);
20 int pthread_attr_setguardsize(pthread_attr_t *attr,
21 size_t guardsize);
22
25 The pthread_attr_getguardsize() function shall get the guardsize
26 attribute in the attr object. This attribute shall be returned in the
27 guardsize parameter.
28 The pthread_attr_setguardsize() function shall set the guardsize
30 attribute in the attr object. The new value of this attribute shall be
31 obtained from the guardsize parameter. If guardsize is zero, a guard
32 area shall not be provided for threads created with attr. If guardsize
33 is greater than zero, a guard area of at least size guardsize bytes
34 shall be provided for each thread created with attr.
35 The guardsize attribute controls the size of the guard area for the
37 created thread's stack. The guardsize attribute provides protection
38 against overflow of the stack pointer. If a thread's stack is created
39 with guard protection, the implementation allocates extra memory at the
40 overflow end of the stack as a buffer against stack overflow of the
41 stack pointer. If an application overflows into this buffer an error
42 shall result (possibly in a SIGSEGV signal being delivered to the
43 thread).
44 A conforming implementation may round up the value contained in guard‐
46 size to a multiple of the configurable system variable {PAGESIZE} (see
47 <sys/mman.h>). If an implementation rounds up the value of guardsize to
48 a multiple of {PAGESIZE}, a call to pthread_attr_getguardsize() speci‐
49 fying attr shall store in the guardsize parameter the guard size speci‐
50 fied by the previous pthread_attr_setguardsize() function call.
51 The default value of the guardsize attribute is {PAGESIZE} bytes. The
53 actual value of {PAGESIZE} is implementation-defined.
54 If the stackaddr or stack attribute has been set (that is, the caller
56 is allocating and managing its own thread stacks), the guardsize
57 attribute shall be ignored and no protection shall be provided by the
58 implementation. It is the responsibility of the application to manage
59 stack overflow along with stack allocation and management in this case.
60
62 If successful, the pthread_attr_getguardsize() and pthread_attr_set‐
63 guardsize() functions shall return zero; otherwise, an error number
64 shall be returned to indicate the error.
65
67 The pthread_attr_getguardsize() and pthread_attr_setguardsize() func‐
68 tions shall fail if:
69 EINVAL The attribute attr is invalid.
71 EINVAL The parameter guardsize is invalid.
73 These functions shall not return an error code of [EINTR].
76 The following sections are informative.
78
80 None.
81
83 None.
84
86 The guardsize attribute is provided to the application for two reasons:
87 1. Overflow protection can potentially result in wasted system
89 resources. An application that creates a large number of threads,
90 and which knows its threads never overflow their stack, can save
91 system resources by turning off guard areas.
92 2. When threads allocate large data structures on the stack, large
94 guard areas may be needed to detect stack overflow.
95
97 None.
98
100 The Base Definitions volume of IEEE Std 1003.1-2001, <pthread.h>,
101 <sys/mman.h>
102
104 Portions of this text are reprinted and reproduced in electronic form
105 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
106 -- Portable Operating System Interface (POSIX), The Open Group Base
107 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
108 Electrical and Electronics Engineers, Inc and The Open Group. In the
109 event of any discrepancy between this version and the original IEEE and
110 The Open Group Standard, the original IEEE and The Open Group Standard
111 is the referee document. The original Standard can be obtained online
112 at http://www.opengroup.org/unix/online.html .
113IEEE/The Open Group 2003 PTHREAD_ATTR_GETGUARDSIZE(3P)