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

[Corinna Vinschen <vinschen@redhat.com>]

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.

In install_minimal_symbols(), line 864ff is a loop, which strips the
first character from SYMBOL_LINKAGE_NAME, if that character equals
get_symbol_leading_char (objfile->obfd).  This leading_char is set
to "_".

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?!?

Corinna

-- 
Corinna Vinschen
Cygwin Developer
Red Hat, Inc.