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authorhongbotian <hongbo.tianhongbo@huawei.com>2015-11-30 01:45:08 -0500
committerhongbotian <hongbo.tianhongbo@huawei.com>2015-11-30 01:45:08 -0500
commite8ec7aa8e38a93f5b034ac74cebce5de23710317 (patch)
treeaa031937bf856c1f8d6ad7877b8d2cb0224da5ef /rubbos/app/httpd-2.0.64/docs/manual/developer/debugging.html.en
parentcc40af334e619bb549038238507407866f774f8f (diff)
upload http
JIRA: BOTTLENECK-10 Change-Id: I7598427ff904df438ce77c2819ee48ac75ffa8da Signed-off-by: hongbotian <hongbo.tianhongbo@huawei.com>
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+<?xml version="1.0" encoding="ISO-8859-1"?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
+ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+ This file is generated from xml source: DO NOT EDIT
+ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+ -->
+<title>Debugging Memory Allocation in APR - Apache HTTP Server</title>
+<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
+<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
+<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" />
+<link href="../images/favicon.ico" rel="shortcut icon" /></head>
+<body id="manual-page"><div id="page-header">
+<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
+<p class="apache">Apache HTTP Server Version 2.0</p>
+<img alt="" src="../images/feather.gif" /></div>
+<div class="up"><a href="./"><img title="&lt;-" alt="&lt;-" src="../images/left.gif" /></a></div>
+<div id="path">
+<a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="../">Version 2.0</a> &gt; <a href="./">Developer Documentation</a></div><div id="page-content"><div id="preamble"><h1>Debugging Memory Allocation in APR</h1>
+<div class="toplang">
+<p><span>Available Languages: </span><a href="../en/developer/debugging.html" title="English">&nbsp;en&nbsp;</a></p>
+</div>
+
+ <p>The allocation mechanism's within APR have a number of debugging modes
+ that can be used to assist in finding memory problems. This document
+ describes the modes available and gives instructions on activating
+ them.</p>
+</div>
+<div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#options">Available debugging options</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#combo">Allowable Combinations</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#howto">Activating Debugging Options</a></li>
+</ul></div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="options" id="options">Available debugging options</a></h2>
+ <h3><a name="alloc_debug" id="alloc_debug">Allocation Debugging - ALLOC_DEBUG</a></h3>
+
+
+ <div class="note">Debugging support: Define this to enable code which
+ helps detect re-use of <code>free()</code>d memory and other such
+ nonsense.</div>
+
+ <p>The theory is simple. The <code>FILL_BYTE</code> (<code>0xa5</code>)
+ is written over all <code>malloc</code>'d memory as we receive it, and
+ is written over everything that we free up during a
+ <code>clear_pool</code>. We check that blocks on the free list always
+ have the <code>FILL_BYTE</code> in them, and we check during
+ <code>palloc()</code> that the bytes still have <code>FILL_BYTE</code>
+ in them. If you ever see garbage URLs or whatnot containing lots
+ of <code>0xa5</code>s then you know something used data that's been
+ freed or uninitialized.</p>
+
+
+ <h3><a name="alloc_use_malloc" id="alloc_use_malloc">Malloc Support - ALLOC_USE_MALLOC</a></h3>
+
+
+ <div class="note">If defined all allocations will be done with
+ <code>malloc()</code> and <code>free()</code>d appropriately at the
+ end.</div>
+
+ <p>This is intended to be used with something like Electric
+ Fence or Purify to help detect memory problems. Note that if
+ you're using efence then you should also add in <code>ALLOC_DEBUG</code>.
+ But don't add in <code>ALLOC_DEBUG</code> if you're using Purify because
+ <code>ALLOC_DEBUG</code> would hide all the uninitialized read errors
+ that Purify can diagnose.</p>
+
+
+ <h3><a name="pool_debug" id="pool_debug">Pool Debugging - POOL_DEBUG</a></h3>
+ <div class="note">This is intended to detect cases where the wrong pool is
+ used when assigning data to an object in another pool.</div>
+
+ <p>In particular, it causes the <code>table_{set,add,merge}n</code>
+ routines to check that their arguments are safe for the
+ <code>apr_table_t</code> they're being placed in. It currently only works
+ with the unix multiprocess model, but could be extended to others.</p>
+
+
+ <h3><a name="make_table_profile" id="make_table_profile">Table Debugging - MAKE_TABLE_PROFILE</a></h3>
+
+
+ <div class="note">Provide diagnostic information about make_table() calls
+ which are possibly too small.</div>
+
+ <p>This requires a recent gcc which supports
+ <code>__builtin_return_address()</code>. The error_log output will be a
+ message such as:</p>
+ <div class="example"><p><code>
+ table_push: apr_table_t created by 0x804d874 hit limit of 10
+ </code></p></div>
+
+ <p>Use <code>l *0x804d874</code> to find the
+ source that corresponds to. It indicates that a <code>apr_table_t</code>
+ allocated by a call at that address has possibly too small an
+ initial <code>apr_table_t</code> size guess.</p>
+
+
+ <h3><a name="alloc_stats" id="alloc_stats">Allocation Statistics - ALLOC_STATS</a></h3>
+
+
+ <div class="note">Provide some statistics on the cost of allocations.</div>
+
+ <p>This requires a bit of an understanding of how alloc.c works.</p>
+
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="combo" id="combo">Allowable Combinations</a></h2>
+
+ <p>Not all the options outlined above can be activated at the
+ same time. the following table gives more information.</p>
+
+ <table class="bordered"><tr class="header"><th />
+ <th>ALLOC DEBUG</th>
+ <th>ALLOC USE MALLOC</th>
+ <th>POOL DEBUG</th>
+ <th>MAKE TABLE PROFILE</th>
+ <th>ALLOC STATS</th></tr>
+<tr><th>ALLOC DEBUG</th>
+ <td>-</td><td>No</td><td>Yes</td><td>Yes</td><td>Yes</td></tr>
+<tr class="odd"><th>ALLOC USE MALLOC</th>
+ <td>No</td><td>-</td><td>No</td><td>No</td><td>No</td></tr>
+<tr><th>POOL DEBUG</th>
+ <td>Yes</td><td>No</td><td>-</td><td>Yes</td><td>Yes</td></tr>
+<tr class="odd"><th>MAKE TABLE PROFILE</th>
+ <td>Yes</td><td>No</td><td>Yes</td><td>-</td><td>Yes</td></tr>
+<tr><th>ALLOC STATS</th>
+ <td>Yes</td><td>No</td><td>Yes</td><td>Yes</td><td>-</td></tr>
+</table>
+
+ <p>Additionally the debugging options are not suitable for
+ multi-threaded versions of the server. When trying to debug
+ with these options the server should be started in single
+ process mode.</p>
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="howto" id="howto">Activating Debugging Options</a></h2>
+
+ <p>The various options for debugging memory are now enabled in
+ the <code>apr_general.h</code> header file in APR. The various options are
+ enabled by uncommenting the define for the option you wish to
+ use. The section of the code currently looks like this
+ (<em>contained in srclib/apr/include/apr_pools.h</em>)</p>
+
+ <div class="example"><p><code>
+ /*<br />
+ #define ALLOC_DEBUG<br />
+ #define POOL_DEBUG<br />
+ #define ALLOC_USE_MALLOC<br />
+ #define MAKE_TABLE_PROFILE<br />
+ #define ALLOC_STATS<br />
+ */<br />
+ <br />
+ typedef struct ap_pool_t {<br />
+ <span class="indent">
+ union block_hdr *first;<br />
+ union block_hdr *last;<br />
+ struct cleanup *cleanups;<br />
+ struct process_chain *subprocesses;<br />
+ struct ap_pool_t *sub_pools;<br />
+ struct ap_pool_t *sub_next;<br />
+ struct ap_pool_t *sub_prev;<br />
+ struct ap_pool_t *parent;<br />
+ char *free_first_avail;<br />
+ </span>
+ #ifdef ALLOC_USE_MALLOC<br />
+ <span class="indent">
+ void *allocation_list;<br />
+ </span>
+ #endif<br />
+ #ifdef POOL_DEBUG<br />
+ <span class="indent">
+ struct ap_pool_t *joined;<br />
+ </span>
+ #endif<br />
+ <span class="indent">
+ int (*apr_abort)(int retcode);<br />
+ struct datastruct *prog_data;<br />
+ </span>
+ } ap_pool_t;
+ </code></p></div>
+
+ <p>To enable allocation debugging simply move the <code>#define
+ ALLOC_DEBUG</code> above the start of the comments block and rebuild
+ the server.</p>
+
+ <div class="note"><h3>Note</h3>
+ <p>In order to use the various options the server <strong>must</strong>
+ be rebuilt after editing the header file.</p>
+ </div>
+</div></div>
+<div class="bottomlang">
+<p><span>Available Languages: </span><a href="../en/developer/debugging.html" title="English">&nbsp;en&nbsp;</a></p>
+</div><div id="footer">
+<p class="apache">Copyright 2009 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
+<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div>
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