Re: DW_AT_specification and partial symtabs

[Elena Zannoni <ezannoni at redhat dot com>]

Daniel Jacobowitz writes:
 > On Thu, Jun 12, 2003 at 10:01:38AM -0700, David Carlton wrote:
 > > One of the main issues that I'm dealing with on my branch is getting
 > > nested types to work right in C++ (with DWARF 2): these have the
 > > characteristic that they depend on the hierarchical structure of the
 > > debug info to a greater extent than, as far as I can tell, anything
 > > that mainline GDB currently does.  The reason for this is that, to
 > > deduce a nested type's name, you really have to know where it lives in
 > > the hierarchical structure, so you can add whatever prefixes are
 > > appropriate to its DW_AT_name.  (With non-types, we (over)use mangled
 > > names for this sort of thing, so it's not such a big deal there.)
 > 
 > > Unfortunately, there's no way to get at that information at all with
 > > the current psymtab reader: it tries to march from top-level DIE to
 > > top-level DIE without building up a tree of DIEs.  So it seems to me
 > > that I have no choice but to have the psymtab reader build up a tree
 > > of DIEs before it starts reading, just like the symtab reader does.
 > > 
 > > Comments?  Suggestions?  Ideas for how to make the tree that the
 > > psymtab reader builds to be as small as possible?  I'm a little
 > > worried about weird cases like local classes: if I have
 > 

I wonder, if we are not reaching the end of the usefulness of the
psymtabs.  I mean, if we start making the psymtab reader behave like
the symtab reader, how much faster is that going to be, how much
smaller, etc. 
I need to go reread the old threads on this.

elena



 > I'll answer this in more depth in a bit.  For now, something to
 > consider: I would like to add .debug_typenames (spelling?) to GCC -
 > it's an SGI extension, IIRC.  This plus .debug_pubnames should allow us
 > to implement psymtabs entirely without mapping .debug_info.  I believe
 > it handles your case too, since it should have fully qualified
 > typenames.
 > 
 > The implementation may need a little tweaking for space efficiency...
 > 
 > >   void foo ()
 > >   {
 > >     class Local {
 > >     public:
 > >       int mem() {return 1;}
 > >     };
 > > 
 > >     ...
 > >   }
 > > 
 > > then is the compiler allowed to put a definition of Local::mem as a
 > > child of the comp unit die (with a DW_AT_specification pointing to a
 > > DIE inside of foo somewhere)?
 > 
 > I believe so.
 > 
 > -- 
 > Daniel Jacobowitz
 > MontaVista Software                         Debian GNU/Linux Developer