Re: [PATCH, ARM] Avoid pulling in unwinder for 64-bit division

[Ian Lance Taylor <iant at google dot com>]

Julian Brown <julian@codesourcery.com> writes:

> On Wed, 28 Oct 2009 07:49:18 -0700
> Ian Lance Taylor <iant@google.com> wrote:
>
>> Julian Brown <julian@codesourcery.com> writes:
>> 
>> > This patch sets compilation flags for the relevant parts of libgcc
>> > on ARM such that the unwinder is not unnecessarily pulled in to the
>> > linked executable when 64-bit division is used. This can be quite a
>> > significant space saving on bare-metal systems.
>> 
>> I think the question here is what should happen when a division by
>> zero occurs.  I believe that is why we currently pass
>> -fnon-call-exceptions.  What happens on ARM if you divide by zero?  In
>> particular, what happens if you divide by zero in a program which is
>> itself compiled with -fnon-call-exceptions, and which expects to catch
>> a division by zero exception?  Do 32-bit divisions and 64-bit
>> divisions behave in the same way?
>
> A follow-up patch to address division-by-zero problems (the handling
> not being ARM EABI-compliant) is here:
>
>   http://gcc.gnu.org/ml/gcc-patches/2009-10/msg01661.html
>
> (These patches both date from some time ago: I believe throwing an
> exception from a divide-by-zero handler should work correctly after
> the latter patch is applied, but I've not tested that recently.)

Well, I'll let the ARM maintainers decide about that patch.

Looking again at
    http://gcc.gnu.org/ml/gcc-patches/2009-10/msg01618.html
I don't understand why you want to change shared-object.mk or
static-object.mk.

I'll approve the change to libgcc/Makefile.in if the ARM maintainers
approve the rest of the patch.

Ian