Re: [cdt-debug-dev] Events and CDI

["Mikhail Khodjaiants" <mikhailk@xxxxxxx>]

Matthew,

Please, see my comments inline.

----- Original Message ----- 
From: "Matthew Ballance" <matt.ballance@xxxxxxxxx>
To: "CDT Debug developers list" <cdt-debug-dev@xxxxxxxxxxx>
Sent: Tuesday, October 25, 2005 10:07 PM
Subject: Re: [cdt-debug-dev] Events and CDI


> Okay, I'm still looking at this. I'm trying to make sense out of the
> various accessor methods related to variables and the way that the
> GDB/MI integration fires update events...
>
> Attached is a screenshot of what I'm seeing. As far as I can tell, I'm
> implementing all required methods (stubbed out to keep things simple,
> but implemented nonetheless). I have trace messages in the methods, so I
> can see that the 'LocalVariable.getValue()' and  'IntValue.intValue()'
> methods are being called. Yet, the GUI still displays 'pending'. If I
> select different elements in the target view (toggle back and forth
> between stack frames), I can sometimes get a value or two to display.
>
> Here are my two major questions:
>
> - Can I treat methods like StackFrame.createLocalVariable() as a factory
> method (ie it returns a new object each time it's called)? I notice the
> GDB/MI integration does not, but I'm not sure if this is required by CDI
> or by the GDB/MI integration architecture.

There are no restrictions on the "createLocalVariable()" method. The gdb/mi 
integration tries to minimize the number of created var-objects.

> - Are there any good rules of thumb for when to fire Changed events and
> Destroyed events? It's a bit unclear to me, from the GDB/MI source, what
> things should trigger variable update. In general, should I update
> Variables? VariableDescriptors? Values?

The "variable descriptor" is supposed to be a lightweight representation of 
a variable (name, for instance) as oppose of "real variable". The idea 
behind this is that you can request the list of variables names, but you 
need to display the values and get notifications only for selected 
variables. It makes sense for gdb/mi where the creation of a "var-object" is 
costly.
In your implementation, you can combine these two steps in one and create 
ICDIVariable objects when the "getLocalVariabledescriptors" method is called 
(ICDIVariable subclasses ICDIVariableDescriptor).
Change events should be fired by ICDIVariable objects. Firing Destroyed 
event doesn't have an effect in the current implementation, but I would 
suggest to fire it when the variable has been destroyed.

> Thanks in advance!
>
> -Matthew
>
>
>
> On 10/19/05, Mikhail Khodjaiants < mikhailk@xxxxxxx
> <mailto:mikhailk@xxxxxxx> > wrote:
>
> You don't need to fire a CreatedEvent for local variables. The rendering
> of
> the Variables view is asynchronous and messages you see are generated by
> the
> label decorators. All you have to do is to implement the "getValue"
> method
> of ICDIVariable.
>
> ----- Original Message -----
> From: "Matthew Ballance" < matt.ballance@xxxxxxxxx
> <mailto:matt.ballance@xxxxxxxxx> >
> To: "cdt-debug-dev" <  <mailto:cdt-debug-dev@xxxxxxxxxxx>
> cdt-debug-dev@xxxxxxxxxxx>
> Sent: Wednesday, October 19, 2005 9:45 AM
> Subject: [cdt-debug-dev] Events and CDI
>
>
> > Hi all,
> >
> >    I'm working on a debugger that uses the win32 and MS-provided
> > symbol-access APIs to support debugging of Visual Studio-compiled
> > applications. I've run into a problem with supporting variables and
> > thought that a CDI developer or a developer of the CDI gdb-mi debugger
>
> > could give me some pointers...
> >
> >    My first attempt at showing variables was to get method-local
> > variables and parameters working. ICDIStackFrame has a method
> > getLocalVariableDescriptors() that returns an array of variables
> > descriptors. I've implemented this method to return variable
> descriptors
> > for the local parameters of the current stack frame. What I observe in
> > Eclipse is that sometimes the <var-name> = <value> item is displayed
> in
> > the Variables view, sometimes "Pending ..." is displayed, and
> sometimes
> > "..." is shown.
> >
> >    I learned when implemented breakpoints that a CreatedEvent had to
> be
> > posted for each new breakpoint in addition to returning the breakpoint
>
> > object from the set<Type>Breakpoint. I thought that perhaps I needed
> to
> > do something similar for variables. I started by posting
> CreatedEvent's
> > when createLocalVariable() was called, but saw no change in behavior.
> I
> > also tried posting CreateEvent's from getLocalVariableDescriptors().
> > Again, no change in behavior.
> >
> >    Any thoughts on what I may be doing wrong?
> >
> >    Thanks in advance!
> >
> > Thanks and Regards,
> > Matthew
>
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