Problem using py-bt, py-locals, etc. during GDB debugging [solved]

MRAB python at mrabarnett.plus.com
Fri Dec 7 01:37:22 CET 2012


On 2012-12-07 00:22, Mark Shroyer wrote:
> On Thu, Dec 06, 2012 at 04:39:41PM -0500, Mark Shroyer wrote:
>> I'm having trouble with the py-bt, py-locals, etc. GDB commands (from
>> Python's python-gdb.py) while using GDB 7.4 to debug Python 2.7.3; I was
>> wondering if anyone here could offer advice.
>>
>> Briefly, py-bt seems to identify the python stack frames correctly, but
>> shows "(unable to read python frame information)" for each, and likewise
>> py-locals fails with "Unable to read information on python frame".
>
> OK, I took a closer look at this and I've identified the issue; posting
> my fix here in case someone else Googles this.
>
> The problem in my case was that the python-gdb.py extension makes some
> fragile assumptions about the format of values it receives from GDB, and
> I had the line "set output-radix 16" in my .gdbinit, ultimately
> resulting in the extension attempting to convert the string
> representation of a hexadecimal number into an integer.
>
> So there are two easy workarounds:
>
>   1. set output-radix 10 in GDB, or
>
>   2. Patch Python 2.7.3's python-gdb.py as follows:
>
> === 8< =================================
>
> --- python-gdb.py.orig	2012-12-06 15:12:18.666760664 -0500
> +++ python-gdb.py	2012-12-06 19:17:19.588356874 -0500
> @@ -1074,7 +1074,11 @@
>
>
>   def int_from_int(gdbval):
> -    return int(str(gdbval))
> +    int_str = str(gdbval)
> +    if int_str.startswith("0x"):
> +        return int(int_str[2:], 16)
> +    else:
> +        return int(int_str)
>
>
>   def stringify(val):
>
> === 8< =================================
>
> I haven't checked to see whether this also applies to the GDB extension
> for Python 3, though.
>
A shorter fix would be:

def int_from_int(gdbval):
     return int(str(gdbval), 0)


Some examples:

 >>> # Decimal
 >>> int("12", 0)
12
 >>> # Hexadecimal
 >>> int("0x12", 0)
18
 >>> # Octal
 >>> int("012", 0)
10
 >>> # Octal
 >>> int("0o12", 0)
10
 >>> # Binary
 >>> int("0b11", 0)
3




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