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Re: RFA: [buildsym.c] Turn off unused addr bits in linetable
- To: Fernando Nasser <fnasser at redhat dot com>
- Subject: Re: RFA: [buildsym.c] Turn off unused addr bits in linetable
- From: Elena Zannoni <ezannoni at cygnus dot com>
- Date: Sun, 1 Apr 2001 20:37:02 -0400 (EDT)
- Cc: Andrew Cagney <ac131313 at cygnus dot com>, gdb-patches at sources dot redhat dot com
- References: <3AAD70B6.A9C16F36@redhat.com><3AAE3502.BFFE90D2@cygnus.com><3AAE5652.8EDD98FA@redhat.com><3AB15D24.AA6457B9@redhat.com><3AB1733B.FEC3833E@cygnus.com>
Fernando, did you check this in? Thanks for investigating.
BTW. Sh doesn't define ADDR_BITS_REMOVE. But it uses it! I'll have to
fix that.
Elena
Andrew Cagney writes:
> Fernando Nasser wrote:
> >
> > Andrew,
> >
> > I looked at all the targets that define ADDR_BITS_REMOVE() (which are
> > arm, h8500, m88k, mips, pa, w65, z8k and sh) and all that define
> > BREAKPOINT_FROM_PC() (which are arm, mips, mcore and mn10300, as far as
> > I can tell).
> >
> > I am convinced that this is the right thing to do. I really wonder, in
> > some cases, how could it have worked without it (maybe the stub or the
> > OS cleared the bits for us).
>
> I suspect that it is like the 32 bit MIPS - no one was sure how it
> should work. Only when the decision that the 32 bit MIPS was have all
> addresses converted to cannonical form (i.e. sign extend them) did a
> heap of problems get flushed.
>
> I'd lace your patch with comments explaining how the table contains
> cannonical addresses and those addresses don't contain any stray magic
> bits. That way the next person will know where the error is when they
> find a comparison is doing strange things because the addresses don't
> quite match.
>
> > Anyway, there is only one way of knowing it for sure. The only thing we
> > know right now is that ARM is broken without it.
> >
> > OK to commit?
>
> I withdraw my objection. I think the maintainer had already approved
> it.
>
> Thanks for investigating this!
>
> Andrew
>
> PS: A multi-arch footnote (Hi nick :-): At some stage or another, an
> additional interface into BFD is going to be needed so that GDB can ask
> BFD what the architecture/machine tupple for a given address is.
> Details are for much later. This is just a little flag :-)
>