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

[Dave Anderson]

----- 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