[rfa] Deprecate msymbol.info, add msymbol.bfd_symbol?

[Andrew Cagney]

> The first meaning can die as soon as someone can test a coff platform
> with a trivial patch to coffread.c.
> 
> The second meaning is: dbxread.c stores the size of the msym
> in 'msymbol.info'.  It does this in case SOFUN_ADDRESS_MAYBE_MISSING
> is set, in order to synthesize texthigh for that file.
> 
> The third meaning is that arm-tdep.c, m68hc11-tdep.c, mips-tdep.c,
> and sh-tdep.c use msymbol.info as a place to store one or two
> flag bits.

The third meaning needs to be refined slightly.  MAKE_MSYMBOL_SPECIAL, 
for coff, doesn't yet take a "bfd_symbol", in fact, coffread doesn't 
even use BFD's canonicalize_symtab to read the symbols.

>> Consequently, I'd like to propose that "info" be superseeded by a 
>> "struct bfd_symbol *" pointer.
> 
> 
> I don't quite understand your proposal, because there are three
> meanings of "msymbol.info".  Which meanings do you want to supersede?
> Can you put up a little sample code?

If I ignore coff, Arm's arm_pc_is_thumb would look like:

	sym = lookup_minimal_symbol_by_pc (memaddr);
	if (sym && sym->bfd_symbol is "elf like")
	  return (ELF_ST_TYPE (((elf_symbol_type *) 
(sym->bfd_symbol))->internal_elf_sym.st_info) == STT_LOPROC)
	else
	  return 0;

MIPS would be identical.  The existing MAKE_MSYMBOL_SPECIAL wouldn't be 
needed.

The other ELF use in elfread + dbxread:

               /* Pass symbol size field in via BFD.  FIXME!!!  */
               size = ((elf_symbol_type *) sym)->internal_elf_sym.st_size;
               msym = record_minimal_symbol_and_info
                 ((char *) sym->name, symaddr,
                  ms_type, (void *) size, sym->section, objfile);

(having calls to record_minimal_symbol_and_info with a NULL info sux :-) 
could be addressed similar.  Anyone realise that the code assumes elf?

>> The consequence will be that, for a time, the minimal symbol table will 
>> be bigger.
> 
> 
> Here are some numbers from some old test run:
> 
>   msym  0.3 mb
>   psym 11.9 mb
>   sym  30.1 mb
>   mt    8.7 mb  # main_type
> 
> The msym's are not space critical.

Yes, I was secretly assuming that.

> It sucks that msymbol.info is overloaded for three different meanings
> (and none of them is a pointer so we get all those nasty casts).  Let's
> separate it into different fields, and then when the data types are
> nice and correct, if we want the space back (which I think we won't),
> then we can go for 'union' and bit-field things to get the size back
> down.

This could immediatly eliminate two of them.  I think the coff version 
of ARM could also be eliminated if coffread (yea, right ... :-) fully 
utilized BFD.

Andrew