Re: [RFA] minsyms.c: Fix switching to GNU v3 ABI

[Corinna Vinschen <vinschen@redhat.com>]

On Mar 10 11:20, Daniel Jacobowitz wrote:
> On Wed, Mar 10, 2004 at 05:16:17PM +0100, Corinna Vinschen wrote:
> > On Mar 10 11:04, Daniel Jacobowitz wrote:
> > > > > to me like you are having a problem with leading underscores, if I
> > > > > remember my sh-elf-foo correctly.
> > > > 
> > > > Could you tell more about that?  I see a big bunch of symbols beginning
> > > > with "__Z".  Is that what you mean?
> > > 
> > > Yes, precisely.  On sh-elf all symbols are prefixed with an underscore. 
> > > I've been curious for a while about where, precisely, the leading
> > > underscore is supposed to get stripped before we demangle; apparently,
> > > the answer is "not early enough".
> > 
> > Ok, I think I see now what happens.
> > 
> > There are symbols beginning with "_Z" and (the most) beginning with "__Z".
> > 
> > The symbols beginning with "_Z" are correctly recognized as language_cplus.
> > 
> > The symbols beginning with "__Z" are still language_auto after
> > prim_record_minimal_symbol_and_info has been called, since the demangler
> > in libiberty doesn't recognize them.
> 
> Wait a sec, why is that happening?  Either everything should have a
> leading _ or nothing should!

I'm not sure if I understand the question.  All symbols have leading
underscores, some (actually just one!) have one underscore, all others
have two underscores.  I have no idea why that happens, it's what gcc
3.4 generates, I guess.

I checked the C++ demangler in libiberty again and it requires that
the symbols begin with "_Z", not with "__Z".

> > So, after this loop SYMBOL_LINKAGE_NAME begins with "Z" for the first
> > set of symbols (which *are* recognized as cplus variables) and with
> > "_Z" for the second set of symbols (which are still auto).  But now
> > SYMBOL_DEMANGLED_NAME is only called for the second set of symbols
> > and SYMBOL_DEMANGLED_NAME returns NULL for those symbols.
> > 
> > What can we do?!?
> 
> Move the check earlier?  It should not be necessary to change
> SYMBOL_LINKAGE_NAME.  I think you could do this in
> prim_record_minimal_symbol_and_info at the call site of
> SYMBOL_SET_NAMES.

I'm more and more under the impression that the problem is raised due
to a bug in the symbol generation in gcc.  It doesn't seem worth to
change GDB proactively...


Corinna

-- 
Corinna Vinschen
Cygwin Developer
Red Hat, Inc.