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

[Daniel Jacobowitz <drow at mvista dot com>]

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