[PATCH] Option to build bare-metal ARM cross-compiler for arm-none-eabi target without libunwind

[Fredrik Hederstierna <fredrik dot hederstierna at securitas-direct dot com>]

We've been using a bare-metal 'arm-elf' cross-compiler toolchain over the years since GCC 2.95.x/GCC3/GCC4, and it has worked fine.
Now it seems though like the 'arm-elf' target seems obsolete, and we are trying to switch to 'arm-none-eabi'.

Though we use no standard-libs at all, we are really hard bare-metal with our own memcpy() implementation etc.

Now when we try to build GCC 4.7.0 we get errors that libgcc has dependencies on UnWind stuff we cannot get rid of.
The dependencies are caused by some division library functions like _divdi3 that can throw exceptions like division-by-zero.
These exceptions I guess mainly targeting C++/Java exceptions, and we want to avoid dependencies to libunwind when building libgcc for our bare-metal pure C-toolchain.

I attach a patch that adds an option to configure to avoid building libgcc with libunwind dependencies.
The new option is called '--disable-libunwind-exceptions'.

Over the years several people have experienced the same problem, here is some background from the gcc mailinglists:
http://gcc.gnu.org/ml/gcc-help/2012-03/msg00352.html
http://gcc.gnu.org/ml/gcc-help/2009-10/msg00302.html

Please review and comment!
Best Regards,

Fredrik Hederstierna
Securitas Direct AB
Malmoe Sweden

Attachment: disable_libunwind_exceptions.patch
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