RFA: tolerate unavailable struct return values
Daniel Jacobowitz
drow@mvista.com
Sat Nov 24 10:23:00 GMT 2001
On Fri, Nov 30, 2001 at 03:49:52PM -0500, Jim Blandy wrote:
>
> Daniel Jacobowitz <drow@mvista.com> writes:
> > On Thu, Nov 29, 2001 at 05:09:13PM -0500, Jim Blandy wrote:
> > >
> > > On some architectures, it's impossible for GDB to find structs
> > > returned by value. These shouldn't be failures. Should they be
> > > passes?
> >
> > Out of curiousity, which architectures? And to be pedantic, I suspect
> > that it might be "not always possible" rather than actually
> > impossible.
>
> The one I have in mind is the S/390, although I'm pretty sure there
> are others. I've included the bug report I sent to the S/390 GCC
> maintainers below.
>
> One approach would be to hope that the return buffer's address was
> still there in the register it was passed in. But there's no way to
> tell when you're wrong. GDB will just print garbage, and the user
> will think their program is wrong. Better to simply say, "I can't
> find this information reliably", and let the user, who knows their
> program, find another way to get the info --- setting a breakpoint on
> the return statement, or looking at where the caller put the
> structure.
Hmmmm. I wonder if MIPS could ever be affected by this? I don't think
the MIPS ABI specifies that $a0 remains live. It looks as if the value
of $a0 is always returned in $v0 in such functions, though.
--
Daniel Jacobowitz Carnegie Mellon University
MontaVista Software Debian GNU/Linux Developer
More information about the Gdb-patches
mailing list