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From n.@apache.org
Subject cvs commit: httpd-2.0/docs/manual/developer debugging.html.en debugging.xml debugging.html
Date Sat, 05 Apr 2003 00:38:36 GMT
nd          2003/04/04 16:38:36

  Added:       docs/manual/developer debugging.html.en debugging.xml
  Removed:     docs/manual/developer debugging.html
  Log:
  new XML
  
  Revision  Changes    Path
  1.1                  httpd-2.0/docs/manual/developer/debugging.html.en
  
  Index: debugging.html.en
  ===================================================================
  <?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 2.1</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-project/">Documentation</a>
&gt; <a href="../">Version 2.1</a></div><div id="page-content"><div
id="preamble"><h1>Debugging Memory Allocation in APR</h1>
      <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 id="footer">
  <p class="apache">Maintained by the <a href="http://httpd.apache.org/docs-project/">Apache
HTTP Server Documentation Project</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>
  </body></html>
  
  
  1.1                  httpd-2.0/docs/manual/developer/debugging.xml
  
  Index: debugging.xml
  ===================================================================
  <?xml version="1.0" encoding="UTF-8" ?>
  <!DOCTYPE manualpage SYSTEM "../style/manualpage.dtd">
  <?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
  
  <manualpage>
  <relativepath href=".."/>
  
  <title>Debugging Memory Allocation in APR</title>
  
  <summary>
      <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>
  </summary>
    
  <section id="options"><title>Available debugging options</title>
      <section id="alloc_debug">
      <title>Allocation Debugging - ALLOC_DEBUG</title>
  
        <note>Debugging support: Define this to enable code which
        helps detect re-use of <code>free()</code>d memory and other such
        nonsense.</note>
  
        <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>
      </section>
  
      <section id="alloc_use_malloc">
      <title>Malloc Support - ALLOC_USE_MALLOC</title>
  
        <note>If defined all allocations will be done with
        <code>malloc()</code> and <code>free()</code>d appropriately
at the
        end.</note>
  
        <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>
      </section>
  
      <section id="pool_debug"><title>Pool Debugging - POOL_DEBUG</title>
        <note>This is intended to detect cases where the wrong pool is
        used when assigning data to an object in another pool.</note>
  
        <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>
      </section>
  
      <section id="make_table_profile">
      <title>Table Debugging - MAKE_TABLE_PROFILE</title>
  
        <note>Provide diagnostic information about make_table() calls
        which are possibly too small.</note>
  
        <p>This requires a recent gcc which supports
        <code>__builtin_return_address()</code>. The error_log output will be
a
        message such as:</p>
        <example>
          table_push: apr_table_t created by 0x804d874 hit limit of 10
        </example>
  
        <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>
      </section>
  
      <section id="alloc_stats">
      <title>Allocation Statistics -  ALLOC_STATS</title>
  
        <note>Provide some statistics on the cost of allocations.</note>
  
        <p>This requires a bit of an understanding of how alloc.c works.</p>
      </section>
  </section>
  
  <section id="combo"><title>Allowable Combinations</title>
  
      <p>Not all the options outlined above can be activated at the
      same time. the following table gives more information.</p>
  
      <table border="1" style="zebra">
      <tr><th></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><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><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>
  </section>
  
  <section id="howto"><title>Activating Debugging Options</title>
  
      <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>
  
      <example>
        /*<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 />
        <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 />
        </indent>
        #ifdef ALLOC_USE_MALLOC<br />
        <indent>
          void *allocation_list;<br />
        </indent>
        #endif<br />
        #ifdef POOL_DEBUG<br />
        <indent>
          struct ap_pool_t *joined;<br />
        </indent>
        #endif<br />
        <indent>
          int (*apr_abort)(int retcode);<br />
          struct datastruct *prog_data;<br />
        </indent>
        } ap_pool_t;
      </example>
  
      <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>
  
      <note><title>Note</title>
      <p>In order to use the various options the server <strong>must</strong>
      be rebuilt after editing the header file.</p>
      </note>
  </section>
  </manualpage>
  
  
  
  

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