RE: [dsdp-dd-dev] GDB/MI command enhancements

["Marc Khouzam" <marc.khouzam@xxxxxxxxxxxx>]

Hi Nick,

using the flags like --all-values might actually be a good idea.  However, I would like to better understand
the impact it will have on GDB.  Maybe you can shed some light here.

When coding DSF we try to be as efficient as we can, so we try to avoid requesting information from GDB, unless 
we really need it.  In the -var-list-children example, when listing the children of a variable, such as myArray[100], 
a view will only request the values of children that are currently visible to the user (maybe myArray[0] through myArray[4]).  
As the user scrolls to see more elements, the view will request more information.

For this reason, it maybe be better to rely on -var-evaluate-expression for specific elements, instead of getting
all values at once through -var-list-children --all-values, when we may never need them.
However, this entirely depends on the way GDB handles such requests.
>From a GDB point-of-view, how much slower is the response to -var-list-children if --all-values is requested?
Especially in the case of a large list of children.  Is it worth taking the hit up front, to later avoid calling
-var-evaluate-expression multiple times, or is it better to try to avoid unnecessary requests and also stagger
them over time?
 
Would you have an opinion about such performance aspects?

Finally, in some other situations, you are probably right that it would simply be better to use
the options available.  I'm thinking of -var-update <name> for example, where using the option --simple-values
may always be justified.  I will revisit the available options and see if any of them are obvious improvements.

Thanks for pointing this out, and I'm looking forward to your opinion on the performance question above.

Marc

-----Original Message-----
From: dsdp-dd-dev-bounces@xxxxxxxxxxx
[mailto:dsdp-dd-dev-bounces@xxxxxxxxxxx]On Behalf Of Nick Roberts
Sent: Monday, November 12, 2007 22:05
To: dsdp-dd-dev@xxxxxxxxxxx
Subject: [dsdp-dd-dev] GDB/MI command enhancements




There have been many enhancements to the GDB/MI commands.  For example, for
Emacs, I have added "--all-values" as an option to "-var-list-children".
This is faster because it means that GDB doesn't have to fetch the values
through -var-evaluate-expression, and has been part of GDB since 6.4.

Why doesn't DSF use these enhancements?

-- 
Nick                                           http://www.inet.net.nz/~nickrob
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