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