This patch allows a Python value to become "callable", and to execute 
any underlying function by means of an inferior function call.  This is 
implemented purely as a function that is registered within the call 
field on the PyTypeObject. When a Python value is now called, the 
arguments are converted into a list of values. This value list, along 
with the value representing the function, is passed to the 
call_method_by_hand function.

Example

Given this function:

int func1(int a, int b)
{
     return a+b;
}

And loading this function into a value as shown (purely by 
demonstration, how the function is loaded into a value is up to you):

p/x func1
0x40048
python some_value = gdb.history(0)

Results in:

python print some_value(10,20)
30

This can also be applied within pretty printers. There is a test that 
demonstrates how to perform these calls within a pretty printer included 
with the patch.

This function does not test the sanity, or the number of arguments, or 
type checks the arguments before the function is passed to 
call_function_by_hand. It simply assembles the arguments, converts them 
from Python, passes them to the call function and then converts any GDB 
exceptions to Python exceptions.

Regards

Phil

ChangeLog

2009-09-09  Phil Muldoon <pmuldoon@redhat.com>

     * python/python-value.c (valpy_call): New function.
     (value_object_type): Register valpy_call as tp_call function.

Documentation ChangeLog

2009-09-09  Phil Muldoon <pmuldoon@redhat.com>

     * gdb.texinfo (Values From Inferior): Document inferior function
     calls on Python values.

Testsuite ChangeLog

2009-09-09  Phil Muldoon <pmuldoon@redhat.com>

     * gdb.python/python-value.c (func1): New function for inferior
     function call test.
     (func2): Likewise.
     * gdb.python/python-prettyprint.c (InferiorCall): New Class for
     pretty printer test.
     * gdb.python/python-prettyprint.py (pp_inferiorcall): New printer.
     (register_pretty_printers): Register pp_inferiorcall.
     * gdb.python/python-prettyprint.exp (run_lang_tests): Add inferior
     function call tests.
     * gdb.python/python-value.exp (test_inferior_function_call): New
     function.