struct environment

[Andrew Cagney]

> On Tue, Sep 17, 2002 at 03:47:36AM -0400, Andrew Cagney wrote:
> 
>> Btw, try ``struct nametab''?  These are just tables for mapping a name 
>> onto a symbol?
> 
> 
> Hmm..
> 
> 
>> Having also gone over the original thread, two things come to mind:
>> 
>> - what effect will this have on GDB's foot print?  The original proposal 
>> was to put these things everwhere (structs, unions, ...).  I don't think 
>> that is necessary and would cause serious bloat.  Instead, initially, I 
>> think these tables could be simple linear lists (that is what ``struct 
>> block'' currently implements so it can't be any worse :-) (just the 
>> global / final table is special :-).
> 
> 
> Why do you think this will cause any bloat?  This is why David
> suggested a model of block with a linear list implementation.

That is good news, the early discussion was describing a totally generic 
implementation being applied to everything.  Can I assume that no one 
has immediate plans for adding this to the type system?

>> - Am I correct to think that the objective is to create a directed 
>> acyclic graph of nametabs and have lookups search through each in turn.
> 
> 
> Well, sort of.  It won't be a DAG necessarily (I think that mutual
> "using" statements are legal in C++; I remember a GCC bug involving
> them was fixed not long ago), and it will be somewhat complicated
> figuring out which ones to look up (namespace links are different than
> block scope links).

Don't forget that GDB doesn't need to model the language.  Just the 
namespace behavior at a given PC.  The effect of "using" would be to 
just grow a nametab in someway.

>> In terms of operations, I would concentrate on determing exactly GDB 
>> needs (rather than you think it needs)   GDB is 15 years old so chance 
>> has it the operations have been identified already.  I know of two 
>> operations off hand:
>> 	print foo
>> which gets turned into struct symbol *lookup("foo",``block'') and,
>> 	print foo<tab>
>> which turns into ``const char **tabexpand("foo", ``block'')''.  Any others?
> 
> 
> At least iterate over all, search regexp.

Yes (iterate over would come from things like ``info locals'').  Regex 
(I know it's used somewhere)?

Andrew