Re: C++ nested classes, namespaces, structs, and compound statements

Daniel Jacobowitz
2002-04-16T21:58:49Z

On Tue, Apr 16, 2002 at 04:46:27PM -0500, Jim Blandy wrote:
>
> Daniel Jacobowitz <drow@mvista.com> writes:
> > > Okay, I think I see. You're preserving the distinctions implicit in
> > > the existing structures (fields and symbols are separate),
> > > distinguishing types from symbols (i.e. an entry for a typedef would
> > > be an environment_entry whose kind == type_kind, instead of a symbol
> > > with an address class of LOC_TYPEDEF), and positing that namespaces
> > > would be a fourth kind of thing. The `data' field would point to a
> > > `struct type' or a `struct field', or whatever.
> >
> > Yes, that's right. There's also transparent scopes (which might be a
> > special kind of namespace... or not). By that I mean {} enclosed
> > regions with their own local variables. A function belongs to a
> > namespace, a namespace does not enclose a particular range of PCs - but
> > a scope does enclose a particular PC range. Hopefully but not
> > necessarily a single contiguous range. Optimization or explicit
> > .section directives could break it up.
>
> At the moment GDB assumes they're contiguous. (Of course.) Dwarf 3
> allows one to describe lexical blocks that occupy discontinuous
> address ranges, but we don't read that. (Of course.)

Of course :)

> But why would lexical blocks occur in an environment? They don't
> generally have names. Functions do, but I would say a function "has
> a" lexical block, rather than saying it "is a" lexical block.

A function can have local types (in GNU C, and possibly in standard C++,
etc.). It also contains lexical blocks with no names.

int
foo()
{
typedef int x;
return (x) 1;
}

The type 'x' is local to foo() in this example. The DWARF-2
information supports this interpretation.

--
Daniel Jacobowitz Carnegie Mellon University
MontaVista Software Debian GNU/Linux Developer