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<h3 class="section">9.5 Specifying Source Directories</h3>

<p><a name="index-source-path-453"></a><a name="index-directories-for-source-files-454"></a>Executable programs sometimes do not record the directories of the source
files from which they were compiled, just the names.  Even when they do,
the directories could be moved between the compilation and your debugging
session.  <span class="sc">gdb</span> has a list of directories to search for source files;
this is called the <dfn>source path</dfn>.  Each time <span class="sc">gdb</span> wants a source file,
it tries all the directories in the list, in the order they are present
in the list, until it finds a file with the desired name.

   <p>For example, suppose an executable references the file
<samp><span class="file">/usr/src/foo-1.0/lib/foo.c</span></samp>, and our source path is
<samp><span class="file">/mnt/cross</span></samp>.  The file is first looked up literally; if this
fails, <samp><span class="file">/mnt/cross/usr/src/foo-1.0/lib/foo.c</span></samp> is tried; if this
fails, <samp><span class="file">/mnt/cross/foo.c</span></samp> is opened; if this fails, an error
message is printed.  <span class="sc">gdb</span> does not look up the parts of the
source file name, such as <samp><span class="file">/mnt/cross/src/foo-1.0/lib/foo.c</span></samp>. 
Likewise, the subdirectories of the source path are not searched: if
the source path is <samp><span class="file">/mnt/cross</span></samp>, and the binary refers to
<samp><span class="file">foo.c</span></samp>, <span class="sc">gdb</span> would not find it under
<samp><span class="file">/mnt/cross/usr/src/foo-1.0/lib</span></samp>.

   <p>Plain file names, relative file names with leading directories, file
names containing dots, etc. are all treated as described above; for
instance, if the source path is <samp><span class="file">/mnt/cross</span></samp>, and the source file
is recorded as <samp><span class="file">../lib/foo.c</span></samp>, <span class="sc">gdb</span> would first try
<samp><span class="file">../lib/foo.c</span></samp>, then <samp><span class="file">/mnt/cross/../lib/foo.c</span></samp>, and after
that&mdash;<samp><span class="file">/mnt/cross/foo.c</span></samp>.

   <p>Note that the executable search path is <em>not</em> used to locate the
source files.

   <p>Whenever you reset or rearrange the source path, <span class="sc">gdb</span> clears out
any information it has cached about where source files are found and where
each line is in the file.

   <p><a name="index-directory-455"></a><a name="index-dir-456"></a>When you start <span class="sc">gdb</span>, its source path includes only &lsquo;<samp><span class="samp">cdir</span></samp>&rsquo;
and &lsquo;<samp><span class="samp">cwd</span></samp>&rsquo;, in that order. 
To add other directories, use the <code>directory</code> command.

   <p>The search path is used to find both program source files and <span class="sc">gdb</span>
script files (read using the &lsquo;<samp><span class="samp">-command</span></samp>&rsquo; option and &lsquo;<samp><span class="samp">source</span></samp>&rsquo; command).

   <p>In addition to the source path, <span class="sc">gdb</span> provides a set of commands
that manage a list of source path substitution rules.  A <dfn>substitution
rule</dfn> specifies how to rewrite source directories stored in the program's
debug information in case the sources were moved to a different
directory between compilation and debugging.  A rule is made of
two strings, the first specifying what needs to be rewritten in
the path, and the second specifying how it should be rewritten. 
In <a href="set-substitute_002dpath.html#set-substitute_002dpath">set substitute-path</a>, we name these two parts <var>from</var> and
<var>to</var> respectively.  <span class="sc">gdb</span> does a simple string replacement
of <var>from</var> with <var>to</var> at the start of the directory part of the
source file name, and uses that result instead of the original file
name to look up the sources.

   <p>Using the previous example, suppose the <samp><span class="file">foo-1.0</span></samp> tree has been
moved from <samp><span class="file">/usr/src</span></samp> to <samp><span class="file">/mnt/cross</span></samp>, then you can tell
<span class="sc">gdb</span> to replace <samp><span class="file">/usr/src</span></samp> in all source path names with
<samp><span class="file">/mnt/cross</span></samp>.  The first lookup will then be
<samp><span class="file">/mnt/cross/foo-1.0/lib/foo.c</span></samp> in place of the original location
of <samp><span class="file">/usr/src/foo-1.0/lib/foo.c</span></samp>.  To define a source path
substitution rule, use the <code>set substitute-path</code> command
(see <a href="set-substitute_002dpath.html#set-substitute_002dpath">set substitute-path</a>).

   <p>To avoid unexpected substitution results, a rule is applied only if the
<var>from</var> part of the directory name ends at a directory separator. 
For instance, a rule substituting  <samp><span class="file">/usr/source</span></samp> into
<samp><span class="file">/mnt/cross</span></samp> will be applied to <samp><span class="file">/usr/source/foo-1.0</span></samp> but
not to <samp><span class="file">/usr/sourceware/foo-2.0</span></samp>.  And because the substitution
is applied only at the beginning of the directory name, this rule will
not be applied to <samp><span class="file">/root/usr/source/baz.c</span></samp> either.

   <p>In many cases, you can achieve the same result using the <code>directory</code>
command.  However, <code>set substitute-path</code> can be more efficient in
the case where the sources are organized in a complex tree with multiple
subdirectories.  With the <code>directory</code> command, you need to add each
subdirectory of your project.  If you moved the entire tree while
preserving its internal organization, then <code>set substitute-path</code>
allows you to direct the debugger to all the sources with one single
command.

   <p><code>set substitute-path</code> is also more than just a shortcut command. 
The source path is only used if the file at the original location no
longer exists.  On the other hand, <code>set substitute-path</code> modifies
the debugger behavior to look at the rewritten location instead.  So, if
for any reason a source file that is not relevant to your executable is
located at the original location, a substitution rule is the only
method available to point <span class="sc">gdb</span> at the new location.

   <p><a name="index-g_t_0040samp_007b_002d_002dwith_002drelocated_002dsources_007d-457"></a><a name="index-default-source-path-substitution-458"></a>You can configure a default source path substitution rule by
configuring <span class="sc">gdb</span> with the
&lsquo;<samp><span class="samp">--with-relocated-sources=</span><var>dir</var></samp>&rsquo; option.  The <var>dir</var>
should be the name of a directory under <span class="sc">gdb</span>'s configured
prefix (set with &lsquo;<samp><span class="samp">--prefix</span></samp>&rsquo; or &lsquo;<samp><span class="samp">--exec-prefix</span></samp>&rsquo;), and
directory names in debug information under <var>dir</var> will be adjusted
automatically if the installed <span class="sc">gdb</span> is moved to a new
location.  This is useful if <span class="sc">gdb</span>, libraries or executables
with debug information and corresponding source code are being moved
together.

     <dl>
<dt><code>directory </code><var>dirname</var><code> ...</code><br><dt><code>dir </code><var>dirname</var><code> ...</code><dd>Add directory <var>dirname</var> to the front of the source path.  Several
directory names may be given to this command, separated by &lsquo;<samp><span class="samp">:</span></samp>&rsquo;
(&lsquo;<samp><span class="samp">;</span></samp>&rsquo; on MS-DOS and MS-Windows, where &lsquo;<samp><span class="samp">:</span></samp>&rsquo; usually appears as
part of absolute file names) or
whitespace.  You may specify a directory that is already in the source
path; this moves it forward, so <span class="sc">gdb</span> searches it sooner.

     <p><a name="index-cdir-459"></a><a name="index-cwd-460"></a><a name="index-g_t_0024cdir_0040r_007b_002c-convenience-variable_007d-461"></a><a name="index-g_t_0024cwd_0040r_007b_002c-convenience-variable_007d-462"></a><a name="index-compilation-directory-463"></a><a name="index-current-directory-464"></a><a name="index-working-directory-465"></a><a name="index-directory_002c-current-466"></a><a name="index-directory_002c-compilation-467"></a>You can use the string &lsquo;<samp><span class="samp">$cdir</span></samp>&rsquo; to refer to the compilation
directory (if one is recorded), and &lsquo;<samp><span class="samp">$cwd</span></samp>&rsquo; to refer to the current
working directory.  &lsquo;<samp><span class="samp">$cwd</span></samp>&rsquo; is not the same as &lsquo;<samp><span class="samp">.</span></samp>&rsquo;&mdash;the former
tracks the current working directory as it changes during your <span class="sc">gdb</span>
session, while the latter is immediately expanded to the current
directory at the time you add an entry to the source path.

     <br><dt><code>directory</code><dd>Reset the source path to its default value (&lsquo;<samp><span class="samp">$cdir:$cwd</span></samp>&rsquo; on Unix systems).  This requires confirmation.

     <!-- RET-repeat for @code{directory} is explicitly disabled, but since -->
     <!-- repeating it would be a no-op we do not say that.  (thanks to RMS) -->
     <br><dt><code>show directories</code><dd><a name="index-show-directories-468"></a>Print the source path: show which directories it contains.

     <p><a name="set-substitute_002dpath"></a><br><dt><code>set substitute-path </code><var>from</var> <var>to</var><dd><a name="index-set-substitute_002dpath-469"></a>Define a source path substitution rule, and add it at the end of the
current list of existing substitution rules.  If a rule with the same
<var>from</var> was already defined, then the old rule is also deleted.

     <p>For example, if the file <samp><span class="file">/foo/bar/baz.c</span></samp> was moved to
<samp><span class="file">/mnt/cross/baz.c</span></samp>, then the command

     <pre class="smallexample">          (gdb) set substitute-path /usr/src /mnt/cross
</pre>
     <p class="noindent">will tell <span class="sc">gdb</span> to replace &lsquo;<samp><span class="samp">/usr/src</span></samp>&rsquo; with
&lsquo;<samp><span class="samp">/mnt/cross</span></samp>&rsquo;, which will allow <span class="sc">gdb</span> to find the file
<samp><span class="file">baz.c</span></samp> even though it was moved.

     <p>In the case when more than one substitution rule have been defined,
the rules are evaluated one by one in the order where they have been
defined.  The first one matching, if any, is selected to perform
the substitution.

     <p>For instance, if we had entered the following commands:

     <pre class="smallexample">          (gdb) set substitute-path /usr/src/include /mnt/include
          (gdb) set substitute-path /usr/src /mnt/src
</pre>
     <p class="noindent"><span class="sc">gdb</span> would then rewrite <samp><span class="file">/usr/src/include/defs.h</span></samp> into
<samp><span class="file">/mnt/include/defs.h</span></samp> by using the first rule.  However, it would
use the second rule to rewrite <samp><span class="file">/usr/src/lib/foo.c</span></samp> into
<samp><span class="file">/mnt/src/lib/foo.c</span></samp>.

     <br><dt><code>unset substitute-path [path]</code><dd><a name="index-unset-substitute_002dpath-470"></a>If a path is specified, search the current list of substitution rules
for a rule that would rewrite that path.  Delete that rule if found. 
A warning is emitted by the debugger if no rule could be found.

     <p>If no path is specified, then all substitution rules are deleted.

     <br><dt><code>show substitute-path [path]</code><dd><a name="index-show-substitute_002dpath-471"></a>If a path is specified, then print the source path substitution rule
which would rewrite that path, if any.

     <p>If no path is specified, then print all existing source path substitution
rules.

   </dl>

   <p>If your source path is cluttered with directories that are no longer of
interest, <span class="sc">gdb</span> may sometimes cause confusion by finding the wrong
versions of source.  You can correct the situation as follows:

     <ol type=1 start=1>
<li>Use <code>directory</code> with no argument to reset the source path to its default value.

     <li>Use <code>directory</code> with suitable arguments to reinstall the
directories you want in the source path.  You can add all the
directories in one command.
        </ol>

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