'\" te
.\"  Copyright (c) 1997 Sun Microsystems, Inc.  All Rights Reserved
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License").  You may not use this file except in compliance with the License.
.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.  See the License for the specific language governing permissions and limitations under the License.
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.TH thr_min_stack 3C "12 May 1998" "SunOS 5.11" "Standard C Library Functions"
.SH NAME
thr_min_stack \- return the minimum-allowable size for a thread's stack
.SH SYNOPSIS
.LP
.nf
cc -mt [ \fIflag\fR... ] \fIfile\fR...[ \fIlibrary\fR... ]
#include <thread.h> 

\fBsize_t\fR \fBthr_min_stack\fR(\fB\fR\fIvoid\fR);
.fi

.SH DESCRIPTION
.sp
.LP
When a thread is created with a user-supplied stack, the user must reserve
enough space to run this thread. In a dynamically linked execution environment,
it is very hard to know what the minimum stack requirments are for a thread.
The function \fBthr_min_stack()\fR returns the amount of space needed to
execute a null thread. This is a thread that was created to execute a null
procedure. A thread that does something useful should have a stack size that is
\fBthr_min_stack()\fR + \fI<some increment>\fR\&.
.sp
.LP
Most users should not be creating threads with user-supplied stacks. This
functionality was provided to support applications that wanted complete control
over their execution environment.
.sp
.LP
Typically, users should let the threads library manage stack allocation. The
threads library provides default stacks which should meet the requirements of
any created thread.
.sp
.LP
\fBthr_min_stack()\fR will return the unsigned int \fBTHR_MIN_STACK,\fR which
is the minimum-allowable size for a thread's stack.
.sp
.LP
In this implementation the default size for a user-thread's stack is one
mega-byte. If the second argument to \fBthr_create\fR(3C) is \fBNULL,\fR then
the default stack size for the newly-created thread will be used. Otherwise,
you may specify a stack-size that is at least \fBTHR_MIN_STACK,\fR yet less
than the size of your machine's virtual memory.
.sp
.LP
It is recommended that the default stack size be used.
.sp
.LP
To determine the smallest-allowable size for a thread's stack, execute the
following:
.sp
.in +2
.nf
/* cc thisfile.c -lthread */
#define _REENTRANT
#include <thread.h>
#include <stdio.h>
main(\|)  {
        printf("thr_min_stack(\|) returns %u\en",thr_min_stack(\|));
}
.fi
.in -2

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
MT-LevelMT-Safe
.TE

.SH SEE ALSO
.sp
.LP
\fBattributes\fR(5), \fBstandards\fR(5)