Re: [PATCH] -stack-select-frame

[Jason Molenda <jmolenda@apple.com>]

On Jun 16, 2005, at 4:05 PM, Nick Roberts wrote:

> I thought it would save some time if the user doesn't need to see the
> whole stack.

FWIW we've done a lot of careful timing analysis, and the back &  
forth communication between our GUI and gdb is so fast as to be  
pointless to optimize.  We original considered adding special purpose  
"give Xcode everything it needs to know at a breakpoint hit" type  
commands but when we saw how fast the majority of MI commands can  
execute & be parsed by the GUI, it was obvious that this was not a  
useful area to optimize.  And frankly, in my anecdotal experience,  
MacOS X isn't the fastest OS at things like "two processes talking  
over a pipe".

(one of the parts of this profiling which is especially useful is  
that we have a "mi-timings-enabled" setting.  When it's enabled,  
every MI command reports how long gdb took to complete it, e.g. the  
"time=" bit at the end here:

-> 50-stack-list-frames 0 5
<- 50^done,stack=[frame= 
{level="0",addr="0x0009e7fc",fp="0xbfffe700",func=" [...] ,frame= 
{level="5",addr="0x936265d0",fp="0xbfffeee0",func="-[NSApplication  
run]"}],time= 
{wallclock="0.14353",user="0.00584",system="0.00335",start="1118952348.0 
03847",end="1118952348.147372"}

we have similar timestamps put out by the GUI so when there's a  
slowdown we can establish where time was being spent.)


>>>   enum mi_cmd_result
>>>   mi_cmd_stack_select_frame (char *command, char **argv, int argc)
>>>   {
>>> -   if (!target_has_stack)
>>> -     error (_("mi_cmd_stack_select_frame: No stack."));
>>> -
>>>
>
> Because now GDB will report it as follows:
>
> -stack-select-frame
> &"No stack.\n"
> ^error,msg="No stack."
> (gdb)


You're right, currently it behaves like this:

-stack-select-frame
&"mi_cmd_stack_select_frame: No stack.\n"
^error,msg="mi_cmd_stack_select_frame: No stack."
(gdb)

but select_frame_command () will throw the error eventually, so  
there's no need to do the additional check here.


J