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<title>Debugging with GDB: Line Tables In Python</title>
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<a name="Line-Tables-In-Python"></a>
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<div class="header">
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<p>
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Next: <a href="Breakpoints-In-Python.html#Breakpoints-In-Python" accesskey="n" rel="next">Breakpoints In Python</a>, Previous: <a href="Symbol-Tables-In-Python.html#Symbol-Tables-In-Python" accesskey="p" rel="prev">Symbol Tables In Python</a>, Up: <a href="Python-API.html#Python-API" accesskey="u" rel="up">Python API</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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<hr>
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<a name="Manipulating-line-tables-using-Python"></a>
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<h4 class="subsubsection">23.2.2.28 Manipulating line tables using Python</h4>
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<a name="index-line-tables-in-python"></a>
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<a name="index-gdb_002eLineTable"></a>
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<p>Python code can request and inspect line table information from a
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symbol table that is loaded in <small>GDB</small>. A line table is a
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mapping of source lines to their executable locations in memory. To
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acquire the line table information for a particular symbol table, use
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the <code>linetable</code> function (see <a href="Symbol-Tables-In-Python.html#Symbol-Tables-In-Python">Symbol Tables In Python</a>).
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</p>
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<p>A <code>gdb.LineTable</code> is iterable. The iterator returns
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<code>LineTableEntry</code> objects that correspond to the source line and
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address for each line table entry. <code>LineTableEntry</code> objects have
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the following attributes:
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</p>
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<dl>
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<dt><a name="index-LineTableEntry_002eline"></a>Variable: <strong>LineTableEntry.line</strong></dt>
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<dd><p>The source line number for this line table entry. This number
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corresponds to the actual line of source. This attribute is not
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writable.
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</p></dd></dl>
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<dl>
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<dt><a name="index-LineTableEntry_002epc"></a>Variable: <strong>LineTableEntry.pc</strong></dt>
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<dd><p>The address that is associated with the line table entry where the
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executable code for that source line resides in memory. This
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attribute is not writable.
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</p></dd></dl>
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<p>As there can be multiple addresses for a single source line, you may
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receive multiple <code>LineTableEntry</code> objects with matching
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<code>line</code> attributes, but with different <code>pc</code> attributes. The
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iterator is sorted in ascending <code>pc</code> order. Here is a small
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example illustrating iterating over a line table.
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</p>
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<div class="smallexample">
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<pre class="smallexample">symtab = gdb.selected_frame().find_sal().symtab
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linetable = symtab.linetable()
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for line in linetable:
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print "Line: "+str(line.line)+" Address: "+hex(line.pc)
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</pre></div>
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<p>This will have the following output:
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</p>
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<div class="smallexample">
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<pre class="smallexample">Line: 33 Address: 0x4005c8L
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Line: 37 Address: 0x4005caL
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Line: 39 Address: 0x4005d2L
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Line: 40 Address: 0x4005f8L
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Line: 42 Address: 0x4005ffL
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Line: 44 Address: 0x400608L
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Line: 42 Address: 0x40060cL
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Line: 45 Address: 0x400615L
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</pre></div>
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<p>In addition to being able to iterate over a <code>LineTable</code>, it also
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has the following direct access methods:
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</p>
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<dl>
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<dt><a name="index-LineTable_002eline"></a>Function: <strong>LineTable.line</strong> <em>(line)</em></dt>
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<dd><p>Return a Python <code>Tuple</code> of <code>LineTableEntry</code> objects for any
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entries in the line table for the given <var>line</var>, which specifies
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the source code line. If there are no entries for that source code
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<var>line</var>, the Python <code>None</code> is returned.
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</p></dd></dl>
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<dl>
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<dt><a name="index-LineTable_002ehas_005fline"></a>Function: <strong>LineTable.has_line</strong> <em>(line)</em></dt>
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<dd><p>Return a Python <code>Boolean</code> indicating whether there is an entry in
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the line table for this source line. Return <code>True</code> if an entry
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is found, or <code>False</code> if not.
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</p></dd></dl>
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<dl>
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<dt><a name="index-LineTable_002esource_005flines"></a>Function: <strong>LineTable.source_lines</strong> <em>()</em></dt>
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<dd><p>Return a Python <code>List</code> of the source line numbers in the symbol
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table. Only lines with executable code locations are returned. The
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contents of the <code>List</code> will just be the source line entries
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represented as Python <code>Long</code> values.
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</p></dd></dl>
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<div class="header">
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Next: <a href="Breakpoints-In-Python.html#Breakpoints-In-Python" accesskey="n" rel="next">Breakpoints In Python</a>, Previous: <a href="Symbol-Tables-In-Python.html#Symbol-Tables-In-Python" accesskey="p" rel="prev">Symbol Tables In Python</a>, Up: <a href="Python-API.html#Python-API" accesskey="u" rel="up">Python API</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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