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pthread_attr_setguardsize(3)
NAME
  pthread_attr_setguardsize - Changes the guardsize attribute of the
  specified thread attributes object

SYNOPSIS
  #include <pthread.h>

  int pthread_attr_setguardsize(
	  pthread_attr_t *attr,
	  size_t guardsize );

LIBRARY
  DECthreads POSIX 1003.1c Library (libpthread.so)

STANDARDS
  Interfaces documented on this reference page conform to industry standards
  as follows:

  IEEE Std 1003.1c-1995, POSIX System Application Program Interface

PARAMETERS
  attr
      Address of the thread attributes object whose guardsize attribute is to
      be modified.

  guardsize
      New value for the guardsize attribute of the thread attributes object
      specified by attr.

DESCRIPTION
  This routine uses the value specified in the guardsize argument to set the
  guardsize attribute of the thread attributes object specified in the attr
  argument.

  When creating a thread, use a thread attributes object to specify
  nondefault values for thread attributes. The guardsize attribute of a
  thread attributes object specifies the minimum size (in bytes) of the guard
  area for the stack of a new thread.

  A guard area, with its associated overflow warning area, can help a
  multithreaded program detect overflow of a thread's stack. A guard area is
  a region of no-access memory that DECthreads allocates at the overflow end
  of the thread's stack, following the thread's overflow warning area. If any
  thread attempts to write in the overflow warning area, a stack overflow
  exception occurs. Your program can catch this exception and continue
  processing as long as the thread does not attempt to write in the guard
  area. When any thread attempts to access a memory location within the guard
  area, a memory addressing violation occurs without the possibility of
  recovery.

  A new thread can be created with a default guardsize attribute value.	 This
  value is platform dependent, but will always be at least one "hardware
  protection unit" (that is, at least one page). For more information, see
  the platform-specific appendixes of Guide to DECthreads.

  After this routine is called, due to platform-specific factors DECthreads
  might reserve a larger guard area for the new thread than was specified in
  the guardsize argument. For more information, see the platform-specific
  appendixes of Guide to DECthreads.

  DECthreads allows your program to specify the size of a thread stack's
  guard area for two reasons:

    ·  When a thread allocates large data structures on its stack, a guard
       area with a size greater than the default size might be required to
       detect stack overflow.

    ·  Overflow protection of a thread's stack can potentially waste system
       resources, such as for an application that creates a large number of
       threads that will never overflow their stacks. Your multithreaded
       program can conserve system resources by "turning off" a thread's
       stack guard area--that is, by specifying a guardsize attribute of
       zero.

  If a thread is created using a thread attributes object whose stackaddr
  attribute is set (using the pthread_attr_setstackaddr(3) routine), this
  routine ignores the object's guardsize attribute and provides no thread
  stack guard area for the new thread.

RETURN VALUES
  If an error condition occurs, this routine returns an integer value
  indicating the type of error. Possible return values are as follows:

  0   Successful completion.

  [EINVAL]
      The argument attr is not a valid thread attributes object, or the
      argument guardsize contains an invalid value.

ERRORS
  None

SEE ALSO
  Functions: pthread_attr_init(3), pthread_attr_getguardsize(3),
  pthread_attr_setstacksize(3), pthread_create(3)

  Manuals: Guide to DECthreads and Programmer's Guide

Index for Section 3

Alphabetical listing for P

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