Re: MI: performance of getting stack arguments

[Jim Ingham <jingham@apple.com>]

On Apr 18, 2006, at 12:11 PM, Robert Dewar wrote:

> Jim Ingham wrote:
>> Do you really have a UI that shows the stack arguments for ALL the  
>> frames on the stack?  That's very unusual (and visually a bit  
>> overwhelming, I would imagine).  The usual stack display shows the  
>> stack with just the function names.  Then clicking on any given  
>> stack will populate the arguments for that frame, fill the source  
>> window with the source for that frame, etc...  This way, you only  
>> need to fetch the arguments for the bottom-most frame on the stack  
>> when you stop stepping.  You would only fetch the other stack  
>> arguments if the user specifically requests them.
>
> The ordinary bt from gdb gives this info, and it would be a pain
> not to have it!
>

I dunno.  I find that having a really simple clean stack listing with  
just function names makes it much easier to tell where I am in the  
program.  Most of the time that's what I want to see, not what the  
third argument to the function 10 frames up on the stack was.  If I  
want that, I don't find it a problem to dial it up.  And in the GUI  
all you have to do is click on the frame to see the source &  
arguments.  This seems to work pretty well for folks, at least we get  
lots of suggestions from our users, but nobody's ever asked us to  
change this.

Anyway, this is a "to each his own" kind of thing.  But just keep in  
mind, when you are implementing a GUI debugger that anything you show  
in the UI you are pledging to update every time a step is completed.   
And most folks are pretty sensitive about how long it takes for each  
step to complete. So you do need to be a bit conservative about what  
you display by default.  Adding to this, gdb does get slow as  
programs get large, which makes it even more important to be judicious.

Also, in a GUI much more stuff is visible at once, so if each element  
is too complex then the overall result is noisy and hard to use.  
Visual Studio used by default to show a whole bunch of junk in the  
stack window (pc, args, etc.) and way back when I used it I found it  
really hard to look at for just this reason.  According to the 2005  
Online docs, you can turn all the other info off and display just the  
function name if you want...

Jim