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<div class="titlepage"><div><div><h3 class="title">
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<p>
        Python can be built in a special &#8220;python debugging&#8221; configuration that
        adds extra checks and instrumentation that can be very useful for developers
        of extension modules. The data structures used by the debugging configuration
        contain additional members, so <span class="bold"><strong>a Python executable
        built with python debugging enabled cannot be used with an extension module
        or library compiled without it, and vice-versa.</strong></span>
      </p>
<p>
        Since pre-built &#8220;python debugging&#8221; versions of the Python executable
        and libraries are not supplied with most distributions of Python, <a href="#ftn.building.python_debugging_builds.f0" class="footnote" name="building.python_debugging_builds.f0"><sup class="footnote">[5]</sup></a> and we didn't want to force our users to build them, Boost.Build
        does not automatically enable python debugging in its <code class="computeroutput"><span class="identifier">debug</span></code>
        build variant (which is the default). Instead there is a special build property
        called <code class="computeroutput"><span class="identifier">python</span><span class="special">-</span><span class="identifier">debugging</span></code> that, when used as a build property,
        will define the right preprocessor symbols and select the right libraries
        to link with.
      </p>
<p>
        On unix-variant platforms, the debugging versions of Python's data structures
        will only be used if the symbol <code class="computeroutput"><span class="identifier">Py_DEBUG</span></code>
        is defined. On many windows compilers, when extension modules are built with
        the preprocessor symbol <code class="computeroutput"><span class="identifier">_DEBUG</span></code>,
        Python defaults to force linking with a special debugging version of the
        Python DLL. Since that symbol is very commonly used even when Python is not
        present, Boost.Python temporarily undefines <code class="computeroutput"><span class="identifier">_DEBUG</span></code>
        when <code class="computeroutput"><span class="identifier">Python</span><span class="special">.</span><span class="identifier">h</span></code> is #included from <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">python</span><span class="special">/</span><span class="identifier">detail</span><span class="special">/</span><span class="identifier">wrap_python</span><span class="special">.</span><span class="identifier">hpp</span></code> -
        unless <code class="computeroutput"><span class="identifier">BOOST_DEBUG_PYTHON</span></code>
        is defined. The upshot is that if you want &#8220;python debugging&#8221;and you
        aren't using Boost.Build, you should make sure <code class="computeroutput"><span class="identifier">BOOST_DEBUG_PYTHON</span></code>
        is defined, or python debugging will be suppressed.
      </p>
<div class="footnotes">
<br><hr style="width:100; text-align:left;margin-left: 0">
<div id="ftn.building.python_debugging_builds.f0" class="footnote"><p><a href="#building.python_debugging_builds.f0" class="para"><sup class="para">[5] </sup></a>
          On Unix and similar platforms, a debugging python and associated libraries
          are built by adding --with-pydebug when configuring the Python build. On
          Windows, the debugging version of Python is generated by the "Win32
          Debug" target of the Visual Studio project in the PCBuild subdirectory
          of a full Python source code distribution.
        </p></div>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2002-2015 David
      Abrahams, Stefan Seefeld<br>Copyright &#169; 2002-2015 David Abrahams, Stefan Seefeld<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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