[Crash-utility] [PATCH] add -s option for struct command

[qiaonuohan]

Hello Dave,

After some many discussions, I rewrite the code to an extension module.
What I want is not only the member of structure page, but also other
structure's members. So for the speed of analysing a big number of data
and not obeying your attitude towards the change of struct command, I
made it an extension module.

And about the patch which changes gdb, I create a new method 
print_command_2 to do the work.

At 2012-4-19 20:50, Dave Anderson wrote:
>
>
> ----- Original Message -----
>> At 2012-4-18 21:21, Dave Anderson wrote:
>>> In our original discussions, i thought that I had made it clear
>>> that
>>> the introduction of a new option paradigm with submembers could be
>>> avoided by using, for example, "page._mapcounter" instead of having
>>> to enter "page._mapcount.counter"?  This option makes the struct
>>> command seemingly violate its own rules, and really confuses things.
>>> For example, with your patch, a user would see things like this:
>>
>> The most important reason why I insisted this option is the performance.
>> Both original struct and print command are very slow. When kernel
>> debugger wants to parse a bit amount of data, the performance of
>> original struct and print command is not ideal.
>>
>>>
>>>    crash>   page._mapcount.counter ffffea0000000508 -s
>>>    -1
>>>    crash>   page._mapcount.counter ffffea0000000508
>>>    struct: invalid format: page._mapcount.counter
>>>    crash>   page._mapcount ffffea0000000508
>>>        _mapcount = {
>>>          counter = -1
>>>        }
>>>    crash>   page._mapcount ffffea0000000508 -s
>>>    struct: invalid data structure reference page._mapcount
>>>    crash>
>>
>> An idea of solving this confusion is changing the error information.
>> When users uses "-s" option and error happens, error information
>> suggests to use struct command without "-s" option if it is valid.
>> And vice versa, when error happens without specified "-s" option.
>
> It's not so much the error message wording, it's the usage of a
> completely different option-expression.  And you can still display
> the -s information without the extra submember.
>
>>>
>>> I had suggested that you look into the get_member_data() function
>>> in to the gdb/symtab.c file to access the member offset and size
>>> values.
>>
>> Actually, the function need to be changed a lot to support what I want.
>> I need the information of submember, and I need the position and size of
>> bitfield. After investigation, function print_command_1 hides the data
>> that I want. I know it is not a good idea of modifying this function.
>> But what if a new function which has the similar mechanism with function
>> print_command_1?
>
> Right, that's exactly what I suggested below:
>
>>> I also don't like the idea of modifying the prototype of
>>> the stalwart print_command_1() gdb function, and the creation
>>> of a new gdb command.  Whenever there is a need to update the
>>> embedded gdb version, patches like this can be problematic.
>>> I would prefer that you create a new "GNU_XXXX" #define,
>>> similar to GNU_GET_SYMBOL_TYPE, pass the request through
>>> the gdb_command_funnel switch statement, and write a new
>>> standalone function to accomplish what you have done in the
>>> print_command_1() function.
>
> Dave
>
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>


-- 
--
Regards
Qiao Nuohan


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