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<h3 class="section">B.3 Compiling <span class="sc">gdb</span> in Another Directory</h3>

<p>If you want to run <span class="sc">gdb</span> versions for several host or target machines,
you need a different <code>gdb</code> compiled for each combination of
host and target.  <samp><span class="file">configure</span></samp> is designed to make this easy by
allowing you to generate each configuration in a separate subdirectory,
rather than in the source directory.  If your <code>make</code> program
handles the &lsquo;<samp><span class="samp">VPATH</span></samp>&rsquo; feature (<span class="sc">gnu</span> <code>make</code> does), running
<code>make</code> in each of these directories builds the <code>gdb</code>
program specified there.

   <p>To build <code>gdb</code> in a separate directory, run <samp><span class="file">configure</span></samp>
with the &lsquo;<samp><span class="samp">--srcdir</span></samp>&rsquo; option to specify where to find the source. 
(You also need to specify a path to find <samp><span class="file">configure</span></samp>
itself from your working directory.  If the path to <samp><span class="file">configure</span></samp>
would be the same as the argument to &lsquo;<samp><span class="samp">--srcdir</span></samp>&rsquo;, you can leave out
the &lsquo;<samp><span class="samp">--srcdir</span></samp>&rsquo; option; it is assumed.)

   <p>For example, with version 7.2.50.20100908-cvs, you can build <span class="sc">gdb</span> in a
separate directory for a Sun 4 like this:

<pre class="smallexample">     cd gdb-7.2.50.20100908-cvs
     mkdir ../gdb-sun4
     cd ../gdb-sun4
     ../gdb-7.2.50.20100908-cvs/configure sun4
     make
</pre>
   <p>When <samp><span class="file">configure</span></samp> builds a configuration using a remote source
directory, it creates a tree for the binaries with the same structure
(and using the same names) as the tree under the source directory.  In
the example, you'd find the Sun 4 library <samp><span class="file">libiberty.a</span></samp> in the
directory <samp><span class="file">gdb-sun4/libiberty</span></samp>, and <span class="sc">gdb</span> itself in
<samp><span class="file">gdb-sun4/gdb</span></samp>.

   <p>Make sure that your path to the <samp><span class="file">configure</span></samp> script has just one
instance of <samp><span class="file">gdb</span></samp> in it.  If your path to <samp><span class="file">configure</span></samp> looks
like <samp><span class="file">../gdb-7.2.50.20100908-cvs/gdb/configure</span></samp>, you are configuring only
one subdirectory of <span class="sc">gdb</span>, not the whole package.  This leads to
build errors about missing include files such as <samp><span class="file">bfd/bfd.h</span></samp>.

   <p>One popular reason to build several <span class="sc">gdb</span> configurations in separate
directories is to configure <span class="sc">gdb</span> for cross-compiling (where
<span class="sc">gdb</span> runs on one machine&mdash;the <dfn>host</dfn>&mdash;while debugging
programs that run on another machine&mdash;the <dfn>target</dfn>). 
You specify a cross-debugging target by
giving the &lsquo;<samp><span class="samp">--target=</span><var>target</var></samp>&rsquo; option to <samp><span class="file">configure</span></samp>.

   <p>When you run <code>make</code> to build a program or library, you must run
it in a configured directory&mdash;whatever directory you were in when you
called <samp><span class="file">configure</span></samp> (or one of its subdirectories).

   <p>The <code>Makefile</code> that <samp><span class="file">configure</span></samp> generates in each source
directory also runs recursively.  If you type <code>make</code> in a source
directory such as <samp><span class="file">gdb-7.2.50.20100908-cvs</span></samp> (or in a separate configured
directory configured with &lsquo;<samp><span class="samp">--srcdir=</span><var>dirname</var><span class="samp">/gdb-7.2.50.20100908-cvs</span></samp>&rsquo;), you
will build all the required libraries, and then build GDB.

   <p>When you have multiple hosts or targets configured in separate
directories, you can run <code>make</code> on them in parallel (for example,
if they are NFS-mounted on each of the hosts); they will not interfere
with each other.

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