136 lines
4.5 KiB
HTML
136 lines
4.5 KiB
HTML
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||
|
|
<html>
|
||
|
|
<head>
|
||
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
||
|
|
<meta name="Copyright" content="Copyright (c) 2006 by IBM Corporation">
|
||
|
|
<title>Return values from thread start routines are not integers</title>
|
||
|
|
<!-- Begin Header Records ========================================== -->
|
||
|
|
<!-- All rights reserved. Licensed Materials Property of IBM -->
|
||
|
|
<!-- US Government Users Restricted Rights -->
|
||
|
|
<!-- Use, duplication or disclosure restricted by -->
|
||
|
|
<!-- GSA ADP Schedule Contract with IBM Corp. -->
|
||
|
|
<!-- Change History: -->
|
||
|
|
<!-- YYMMDD USERID Change description -->
|
||
|
|
<!-- NETMG2 SCRIPT A converted by B2H R4.1 (346) (CMS) by HOLTJM at -->
|
||
|
|
<!-- RCHVMW2 on 29 Jan 1999 at 10:01:37 -->
|
||
|
|
<!--File Edited November 2001 -->
|
||
|
|
<!--End Header Records -->
|
||
|
|
<link rel="stylesheet" type="text/css" href="../rzahg/ic.css">
|
||
|
|
</head>
|
||
|
|
<body>
|
||
|
|
<!-- Java sync-link -->
|
||
|
|
<script language="Javascript" src="../rzahg/synch.js" type="text/javascript">
|
||
|
|
</script>
|
||
|
|
|
||
|
|
<a name="Top_Of_Page"></a>
|
||
|
|
|
||
|
|
<h2>Return values from thread start routines are not integers</h2>
|
||
|
|
|
||
|
|
<p>Return values from a thread are defined to be of type <strong>void
|
||
|
|
*</strong>. On some platforms, a void * and an integer can be easily
|
||
|
|
interchanged with no loss of information. Until Version 4 Release 2, this was
|
||
|
|
not true on the iSeries. The iSeries enforces stricter pointer rules to both
|
||
|
|
prevent and detect application bugs or a malicious program's behavior. Thus,
|
||
|
|
when converting integers to pointers by a mechanism not directly supported by
|
||
|
|
your compiler, the valid pointer information is lost, and the pointer is always
|
||
|
|
set to <strong>NULL</strong> (regardless of its binary value).</p>
|
||
|
|
|
||
|
|
<p>New support put into the system in Version 4 Release 2 allows you to store
|
||
|
|
an integer into a pointer, and still have the pointer be
|
||
|
|
non-<strong>NULL</strong>. You cannot store to, read from, or defer a pointer
|
||
|
|
created by this mechanism, but the pointer appears
|
||
|
|
non-<strong>NULL</strong>.</p>
|
||
|
|
|
||
|
|
<p>The macros <strong>__INT</strong>() and <strong>__VOID</strong>() are
|
||
|
|
provided to aid in compatibility and allow you to easily store and retrieve
|
||
|
|
integer information in pointer variables even if your compiler does not support
|
||
|
|
the direct typecast. These macros allow explicit conversion from a pointer to
|
||
|
|
an integer and from an integer to a pointer.</p>
|
||
|
|
|
||
|
|
<p><strong>Note:</strong> The macros <strong>__INT</strong>() and <strong>
|
||
|
|
__VOID</strong>() result in function calls.</p>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
<h3>Example</h3>
|
||
|
|
|
||
|
|
<p>The following example shows the correct way to store and retrieve integer
|
||
|
|
information in pointer variables.</p>
|
||
|
|
|
||
|
|
<p>See <a href="../apiref/aboutapis.htm#codedisclaimer">Code disclaimer information</a>
|
||
|
|
for information pertaining to code examples.</p>
|
||
|
|
|
||
|
|
<pre>
|
||
|
|
#define _MULTI_THREADED
|
||
|
|
#include <pthread.h>
|
||
|
|
#include <stdio.h>
|
||
|
|
#include "check.h"
|
||
|
|
|
||
|
|
int main(int argc, char **argv)
|
||
|
|
{
|
||
|
|
void *status1 = __VOID(5);
|
||
|
|
void *status2 = __VOID(999);
|
||
|
|
|
||
|
|
if (status1 == NULL) {
|
||
|
|
printf("Status1 pointer is NULL\n");
|
||
|
|
}
|
||
|
|
else {
|
||
|
|
printf("Status1 pointer is non-NULL\n");
|
||
|
|
}
|
||
|
|
|
||
|
|
if (status1 == status2) {
|
||
|
|
printf("Both status variables as pointers are equal\n");
|
||
|
|
}
|
||
|
|
else {
|
||
|
|
if (status1 < status2) {
|
||
|
|
printf("Status1 is greater than status2\n");
|
||
|
|
}
|
||
|
|
else {
|
||
|
|
if (status1 < status2) {
|
||
|
|
printf("Status1 is less then status2\n");
|
||
|
|
}
|
||
|
|
else {
|
||
|
|
printf("The pointers are unordered!\n");
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
printf("Pointer values stored in status variables are:\n"
|
||
|
|
" status1 = %.8x %.8x %.8x %.8x\n"
|
||
|
|
" status2 = %.8x %.8x %.8x %.8x\n",
|
||
|
|
status1, status2);
|
||
|
|
printf("Integer values stored in status variables are:\n"
|
||
|
|
" status1 = %d\n"
|
||
|
|
" status2 = %d\n",
|
||
|
|
__INT(status1), __INT(status2));
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
</pre>
|
||
|
|
|
||
|
|
<p><strong>Output:</strong></p>
|
||
|
|
|
||
|
|
<pre>
|
||
|
|
Status1 pointer is non-NULL
|
||
|
|
Status1 is less then status2
|
||
|
|
Pointer values stored in status variables are:
|
||
|
|
status1 = 80000000 00000000 00008302 00000005
|
||
|
|
status2 = 80000000 00000000 00008302 000003e7
|
||
|
|
Integer values stored in status variables are:
|
||
|
|
status1 = 5
|
||
|
|
status2 = 999
|
||
|
|
</pre>
|
||
|
|
|
||
|
|
<hr>
|
||
|
|
<center>
|
||
|
|
<table cellpadding="2" cellspacing="2">
|
||
|
|
<tr align="center">
|
||
|
|
<td valign="middle" align="center">
|
||
|
|
<a href="#Top_Of_Page">Top</a> |
|
||
|
|
<a href="rzah4mst.htm">Pthread APIs</a> |
|
||
|
|
<a href="aplist.htm">APIs by category</a></td>
|
||
|
|
</tr>
|
||
|
|
</table>
|
||
|
|
</center>
|
||
|
|
</body>
|
||
|
|
</html>
|
||
|
|
|