Re: m68k structure return register

[Ralf Corsepius <ralf.corsepius@rtems.org>]

On Wed, 2007-09-19 at 09:31 -0400, Daniel Jacobowitz wrote:
> On Wed, Sep 19, 2007 at 12:24:27PM +0400, Vladimir Prus wrote:
> > > Group I -- monitor.mt -- just m68k-tdep.c
> > > 
> > >         1. m68k-*-aout*                                 a1
> > >         2. m68k-*-coff*                                 a1
> > >         3. m68k-*-elf*                                  a0
> > >         6. m68k-*-uclinuxoldabi*                        a0
> > >         7. m68k-*-uclinux*                              a1
> > >         9. m68k-*-rtems*                                a0
> > > 
> > > In gdb, all target here use the register set in m68k_gdbarch_init -- 
> > > currently A1, which register is wrong for half of targets. I'll get to this
> > > group shortly.
> 
> Which of these are ELF?  I know RTEMS is;
Correct.

> > > The problem is therefore, group I. Notably, for m68k-elf gcc uses
> > > a0, whereas gdb assumes a1. And for m68k-elf, we cannot set
> > > any osabi sniffer. I think that nowdays m68k-elf is probably the most
> > > important target in that group.
> > > 
> > > I would suggest the following:
> > > 
> > > 1. Change gdb's default to use a0 register, so that bare-metal works.
> > > 2. If possible, add osabi sniffers to uclinux, openbsdb and rtems, that
> > > will cause gdb to use a1. 
> 
> OpenBSD is easy.  Shouldn't RTEMS use a0, from your tables above?
Also correct.

Ralf