[LLVMdev] [cfe-dev] Question about '-fno-exceptions' option and 'ExceptionsType' on MCAsmInfo with ARM.

[Rafael Espíndola]

On 8 December 2014 at 06:33, JinGu Kang <jingu at codeplay.com> wrote:
> Hi all
>
> I have a question about the '-fno-exceptions' option with clang and
> 'ExceptionsType' on MCAsmInfo.
>
> I am looking for a way to avoid generating stack unwinding codes when
> compiling with the "armv7-none-linux-gnu" triple using clang. I tried the
> '-fno-exceptions' option in order to do that, but unwinding function symbols
> like '__aeabi_unwind_cpp_pr0' were still present. I think 'ExceptionType' of
> MCAsmInfo is set to ExceptionType::ARM with the above target triple and it
> is not affected by the '-fno-exceptions' option. Am I missing something
> about this, or do we need to provide an interface to disable generation of
> exception codes?

At the MC layer I think we just have a bad name. The flag actually
controls what unwind table format is used. Those are used for
exceptions, but also have other uses.

At least for x86_64 and the .eh_frame section, you can exclude a
function by not including the uwtable attribute. At the clang level
that is done with the -fno-asynchronous-unwind-tables option.

Cheers,
Rafael