This is the mail archive of the
gdb@sources.redhat.com
mailing list for the GDB project.
Re: struct environment
On Tue, Sep 10, 2002 at 05:25:56PM -0700, David Carlton wrote:
> On Fri, 6 Sep 2002 11:06:20 -0400, Daniel Jacobowitz <drow@mvista.com> said:
> > On Thu, Sep 05, 2002 at 01:50:40PM -0700, David Carlton wrote:
>
> >> * There should be a shallow lookup function, i.e. one that looks up a
> >> symbol just in one environment, without going up to a parent
> >> environment. (The latter will get added in once we get to
> >> converting over the global environment.) Maybe
> >>
> >> struct symbol *env_lookup_shallow(struct environment *,
> >> const char *);
>
> > You may need more information than this. Sometimes
> > lookup_block_symbol needs to look up the symbol (i.e. demangled)
> > which has a particular mangled name - this is a wart and not one I'm
> > fond of but it isn't quite ready to die yet.
>
> Fair enough; for now, that function has the exact same arguments as
> lookup_block_symbol (i.e. including the demangled name and the
> namespace).
>
> But, speaking of warts in lookup_block_symbol, what's going on with
> this code?
My memory is hazy, but if you search the archives I suspect you'll see
hints that this all can be deleted. I believe the SYMBOL_ALIASES stuff
has all died; it was never in a standard FSF GCC, just in a Cygnus
product. We'll need to handle something along these lines in the
fortold day of wonders, when we actually have thought of something
clever to do when debugging inlined functions; but for now I doubt
anyone would miss this.
Can anyone confirm my memory?
>
> /* If SYM has aliases, then use any alias that is active
> at the current PC. If no alias is active at the current
> PC, then use the main symbol.
>
> ?!? Is checking the current pc correct? Is this routine
> ever called to look up a symbol from another context?
>
> FIXME: No, it's not correct. If someone sets a
> conditional breakpoint at an address, then the
> breakpoint's `struct expression' should refer to the
> `struct symbol' appropriate for the breakpoint's
> address, which may not be the PC.
>
> Even if it were never called from another context,
> it's totally bizarre for lookup_symbol's behavior to
> depend on the value of the inferior's current PC. We
> should pass in the appropriate PC as well as the
> block. The interface to lookup_symbol should change
> to require the caller to provide a PC. */
>
> if (SYMBOL_ALIASES (sym))
> sym = find_active_alias (sym, read_pc ());
>
> sym_found = sym;
> if (SYMBOL_CLASS (sym) != LOC_ARG &&
> SYMBOL_CLASS (sym) != LOC_LOCAL_ARG &&
> SYMBOL_CLASS (sym) != LOC_REF_ARG &&
> SYMBOL_CLASS (sym) != LOC_REGPARM &&
> SYMBOL_CLASS (sym) != LOC_REGPARM_ADDR &&
> SYMBOL_CLASS (sym) != LOC_BASEREG_ARG)
> {
> break;
> }
>
> Is the SYMBOL_ALIASES bit some sort of stabs mess? And is that if
> expression an attempt to make sure that function arguments whose names
> are shadowed by local variables don't get returned?
>
> For now, I'm planning just to copy all that to env_lookup_shallow, but
> I do wish I understood a little better what it's doing.
>
> David Carlton
> carlton@math.stanford.edu
>
--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer