Line Tables In Python (Debugging with GDB)

23.3.2.29 Manipulating line tables using Python

Python code can request and inspect line table information from a symbol table that is loaded in GDB. 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 linetable function (see Symbol Tables In Python).

A gdb.LineTable is iterable. The iterator returns LineTableEntry objects that correspond to the source line and address for each line table entry. LineTableEntry objects have the following attributes:

Variable: LineTableEntry.line; The source line number for this line table entry. This number corresponds to the actual line of source. This attribute is not writable.

Variable: LineTableEntry.pc; 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.

As there can be multiple addresses for a single source line, you may receive multiple LineTableEntry objects with matching line attributes, but with different pc attributes. The iterator is sorted in ascending pc order. Here is a small example illustrating iterating over a line table.

symtab = gdb.selected_frame().find_sal().symtab
linetable = symtab.linetable()
for line in linetable:
   print ("Line: "+str(line.line)+" Address: "+hex(line.pc))

This will have the following output:

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

In addition to being able to iterate over a LineTable, it also has the following direct access methods:

Function: LineTable.line (line); Return a Python Tuple of LineTableEntry objects for any entries in the line table for the given line, which specifies the source code line. If there are no entries for that source code line, the Python None is returned.

Function: LineTable.has_line (line); Return a Python Boolean indicating whether there is an entry in the line table for this source line. Return True if an entry is found, or False if not.

Function: LineTable.source_lines (); Return a Python List of the source line numbers in the symbol table. Only lines with executable code locations are returned. The contents of the List will just be the source line entries represented as Python Long values.