Re: [rfa:solib] Handle start-address descriptors

[Andrew Cagney <cagney@gnu.org>]

>> > Hmm, a possible problem...  What happens when the target uses function
>> > descriptors, but not for the exec file's start address?  I'm wondering
>> > (ugh) if a separate gdbarch method is required for obtaining the start
>> > address.
> 
>> 
>> Fortunatly a previous patch addressed that problem.  The convert 
>> function is only applied to positively identified descriptors.
> 
> 
> If I'm not mistaken, this problem has been addressed for ppc64 and
> ia64, but not in a generic fashion.  I'm concerned about some other
> ABI (for some other architecture) which has function descriptors, but
> has no easy way to discriminate between descriptors and code
> addresses.  If this ABI specifies that the entry point should refer to
> a code address instead of a descriptor, then we need a more
> complicated mechanism -- perhaps that separate gdbarch method that I
> mentioned earlier.

> I suppose we can wait to do something about this problem until it
> actually arises.  But... since we've identified a potential problem,
> we should at least document it in some appropriate location.  If
> the convert_from_func_ptr_addr() method *must* (due to the way it
> is used elsewhere) contain a discrimination mechanism, then this
> should be mentioned in the documentation.  (BTW, I don't see this
> method documented in gdbint.texinfo.)

Can I encourage you to write this up and add it to the doco?  The method 
most affects the ia64 and ppc/rs6000 targets that you maintain.  There 
is no value-add in taking it any further though.

I'll commit the solib-svr4.c change stuff once I've drained a few other 
pending patches.

Andrew