pthread_attr_setguardsize(3)				     Library Functions Manual				      pthread_attr_setguardsize(3)

NAME

       pthread_attr_setguardsize - Changes the guardsize attribute of the specified thread attributes object.

LIBRARY

       DECthreads POSIX 1003.1c Library (libpthread.so)

SYNOPSIS

       #include <pthread.h>

       int pthread_attr_setguardsize(
			 pthread_attr_t   *attr,
			 size_t 	  guardsize);

STANDARDS

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

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

PARAMETERS

       Address	of  the thread attributes object whose guardsize attribute is to be modified.  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 DEC-
       threads.

       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  pro-
       tection	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:
       Successful completion.  The argument attr is not a valid thread attributes object, or the argument guardsize contains an invalid value.

ERRORS

       None

RELATED INFORMATION

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

       Manuals: Guide to DECthreads and Programmer's Guide delim off

														      pthread_attr_setguardsize(3)