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Extracting strings from Python beyond the terminating NULL

I've been working on the second part of this support for counted strings. I've been puzzled by an issue the last couple of days, and I'm fast running out of ideas ;) My issue is the way that Python extracts strings and passes them back to the C code (and in this case GDB). Here is the narrative:

Now that we have support for counted strings (e.g. value.string(length = 20)) we can capture strings beyond an embedded null (e.g. foo = bar.string(length = 7) where bar is "foo\0bar"). And that works: the full "foo\0bar" is captured. I've been working on handling these counted strings correctly within the Python code. So far so good. Pretty much throughout this code the fully captured string is preserved until it becomes time to turn it back into something GDB can print. At this point we progress:

#3 unicode_to_encoded_string (unicode_str=0x7ffff329de10,
charset=0x743240 "ISO-8859-1")
at ../../archer/gdb/python/python-utils.c:118
#4 0x00000000004bdbb4 in unicode_to_target_string (unicode_str=0x7ffff329de10)
at ../../archer/gdb/python/python-utils.c:133
#5 0x00000000004bdbe9 in python_string_to_target_string (obj=0x7ffff329de10)
at ../../archer/gdb/python/python-value.c:900
#7 0x00000000004b3823 in pretty_print_one_value (printer=0x7ffff31f1368,
out_value=0x7fffffffd830) at ../../archer/gdb/python/python.c:850
#8 0x00000000004b39b6 in print_string_repr (printer=0x7ffff31f1368,
hint=0x11fd900 "string", stream=0xbb8dd0, recurse=0,
options=0x7fffffffd9b0, language=0x77af00)
at ../../archer/gdb/python/python.c:907
at ../../archer/gdb/python/python.c:1220

(The line numbers will be different to your code, mine is modified with the string preservation bits). Anyway, this is where the problem lay. As far as I an see, the only methods available to convert a Python string to a C string are ... you guessed it, null terminated:

And the code in question uses that. So even though we dutifully preserve the embedded null, when the call to Python is made to extract the string, it is terminated on the first null. I'm hoping I missed a length based api call that some python hacker can point me too. PyString_Size(string) actually returns the correct (non null terminated) length btw.

Any ideas?



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