[Crash-utility] right shift of the subtraction result

[Dave Anderson]

----- Original Message -----
> 
> yes, I mean crash command line is lacking support of some advanced arithmetic,
> like this pd command, it doesn't have to send it to gdb;
>
> BTW, these days I am looking for an advanced scripting in crash, does crash
> provide some builtin script language?

Nope.  What you see is what you get.

>
> Or have you looked this pykdump project, to embed a python interpreter sounds
> like a good idea, since gdb has support python scripting as well,
>
> http://sourceforge.net/projects/pykdump/

I'm aware of it, and know that it's useful to those that do use it.  I don't speak
python, and if I really need something that I can't get out of the command set
I find it easier to write something in C for the hidden "test" command, or
by a quick-and-dirty extension module.

Dave


> 
> Thanks,
> 
>      On Wednesday, May 20, 2015 11:17 AM, Dave Anderson <anderson at redhat.com>
>      wrote:
>    
> 
>  
> 
> ----- Original Message -----
> > 
> > Hi Dave,
> > Does this sound like a bug, it need right shift of the subtraction result,
> > crash-git> pd (678324157984276 >> 32)
> > $10 = 157934
> > crash-git> pd ((681670518181331-678324157984276) >> 32)
> > p: gdb request failed: p ((681670518181331-678324157984276)
> > crash-git>
> > 
> > It might be lacking support of some advanced arithmetic, so what is a
> > proper
> > wayto do some arithmetic like this?
> 
> No, it is a crash bug.  If you turn on the console mode, you can see the
> string
> that is passed on to gdb.  Simple example:
>   
>   crash> !tty
>   /dev/pts/8
>   crash> set console /dev/pts/8
>   debug console [2850]: /dev/pts/8
>   console: /dev/pts/8
>   crash> set debug 1
>   debug: 1
>   crash>
>   
> The simple shift case works, and you can see the string that gets passed
> to gdb on the 2nd line of output, in the bracket after gdb_pass_through:
>   
>   crash> pd (15 >> 1)
>   error() trace: 467e99 => 51c147 => 518ca6 => 46eaff
>   gdb_pass_through: [p (15 >> 1)]
>   p: per_cpu_symbol_search((15 >> 1)): NULL
>   $9 = 7
>   crash>
>   
> But by adding the internal set of parentheses, the string gets
> clipped, and just "p ((15+1)" gets passed to gdb:
>   
>   crash> pd ((15+1) >> 1)
>   error() trace: 467e99 => 51c147 => 518ca6 => 46eaff
>   p: per_cpu_symbol_search(((15+1)): NULL
>   gdb_pass_through: [p ((15+1)]
>   error() trace: 467e99 => 51c1e7 => 51a7d5 => 46eaff
>   p: gdb request failed: p ((15+1)
>   crash>
> 
> So it's either related to the crash command line redirection code,
> or in the process_gdb_output() function.  (Feel free to debug it
> if you have the time...)
> 
> Thanks,
>   Dave
> 
> 
>