Re: [boost] [optional] Making optional more debugger friendly

From: Jeffrey Faust (jefffaust_at_[hidden])
Date: 2007-05-23 00:24:59

Fernando Cacciola wrote:

> Hi Jeffrey,
>
> In my experience, changing the class layout based on a preprocessor  
> switch is a very bad idea since it breaks binary compatibility with
> libraries compiled with a different switch, so I strongly suggest
> you/we find a better solution.

I agree.  This is probably the largest drawback.  I'll look further.

> If this functionality is really really needed (read below), I would  
> create a *different* template class to offer it. One such  
> debugger-friendly
> optional<> would replace (rather than add) the bool field with a T* field
> (which would be set to NULL when uninitialized). A different template  
> class makes sure that binary-differing optional's don't mix accidentally  
> (in the same wa a policy-based design does it).

I'll see what I can do with this.  Perhaps this other class will wrap the  
real boost::optional, providing the same interface, and giving an  
additional debug value.  This would make it easier to keep the two classes  
in sync.

> But I'm curious: doesn't a simple dynamic watch, like "*opt", works??   
> That calls a method on the object, yes, but debuggers have been able to  
> do that for decades now.

Quite honestly, I couldn't answer this before I tried it.  Using the  
"Immediate Window" in VC8 gives the error "CXX0034: Error: types  
incompatible with operator."  Now this is a legitimate debugger problem.

Thanks for the idea,

Jeff Faust