This patch adds two related elements to the pretty-printer python 
support.  This patch already exists in the archer-tromey-python branch 
of the archer repository, and here is my submission for the FSF repository.

The first element of the patch adds counted string support to the 
value.string method by an optional length parameter; the second element 
preserves the length of the string and respects embedded nulls in the 
case where a string is regarded as "counted".  This allows the 
preservation of embedded nulls in python value strings as long as a 
length is specified.  If an explicit length is not provided, it reverts 
to the old behaviour of regarding the first null as a sting terminator.

Originally this patch was written as two separate patches:

The counted string support is discussed here in the archer archives:

http://sourceware.org/ml/archer/2009-q2/msg00017.html

And the preservation and embedded nulls in the counted string scenario 
is here:

http://sourceware.org/ml/archer/2009-q2/msg00111.html

Regards

Phil

ChangeLog

2009-06-30 Phil Muldoon <pmuldoon@redhat.com>

     * python/python-internal.h (apply_varobj_pretty_printer): Update
     definition.
     (python_string_to_target_python_string): Add definition.
     * python/python-utils.c (unicode_to_encoded_python_string)
     (unicode_to_target_python_string)
     (python_string_to_target_python_string): New Functions.
     * python/python-prettyprint.c (pretty_print_one_value): Likewise.
     (print_string_repr): Refactor to logic to account for PyObject
     returned strings.
     (apply_varobj_pretty_printer): Likewise.
     * python/python-value.c (valpy_string): Parse length keyword. Use
     length keyword in LA_GET_STRING.
     * varobj.c (value_get_print_value): Refactor logic to account for
     PyObject returned strings.
     * c-lang.c (c_get_string): If the length parameter is specified,
     use that. Return value in characters. Update comments.
        * language.h: Update c_get_string prototype comments.

Testsuite ChangeLog:

2009-06-30 Phil Muldoon <pmuldoon@redhat.com>

     * gdb.python/python-prettyprint.c: Add counted null string
     structure.
     * gdb.python/python-prettyprint.exp: Print null string. Test for
     embedded nulls.
     * gdb.python/python-prettyprint.py (pp_ns): New
     Function.
     * gdb.python/python-value.exp (test_value_in_inferior): Add
     variable length string fetch tests.
     * gdb.python/python-value.c (main): Add strings for string fetch tests.

Documentation ChangeLog

2009-06-30  Phil Muldoon <pmuldoon@redhat.com>

     * gdb.texinfo (Values From Inferior): Add length parameter
     description.