[cfe-dev] Does clang support -fno-enforce-eh-specs option of gcc

[Devchandra L Meetei]

I guess that will make migration from gcc easy a bit.


On Wed, Nov 14, 2012 at 3:49 AM, Matthieu Monrocq <
matthieu.monrocq at gmail.com> wrote:

>
>
> On Tue, Nov 13, 2012 at 9:15 PM, Richard Smith <richard at metafoo.co.uk>wrote:
>
>> On Tue, Nov 13, 2012 at 10:51 AM, Matthieu Monrocq
>> <matthieu.monrocq at gmail.com> wrote:
>> >
>> >
>> > On Tue, Nov 13, 2012 at 7:44 PM, Konstantin Tokarev <annulen at yandex.ru>
>> > wrote:
>> >>
>> >>
>> >> 13.11.2012, 22:39, "Devchandra L Meetei" <dlmeetei at gmail.com>:
>> >> > Hi all
>> >> > is the above flag supported.
>> >>
>> >> No.
>> >>
>> >> > Will also appreciate if some one can tell best practices to follow
>> while
>> >> > using clang for reducing size of the resultant binaries?
>> >>
>> >> -Os -fno-rtti -fno-exceptions
>> >>
>> >> --
>> >> Regards,
>> >> Konstantin
>> >
>> >
>> > I would note that this not exactly similar:
>> >
>> > -fno-enforce-eh-specs
>> >     Don't check for violation of exception specifications at runtime.
>> This
>> > option violates the C++ standard, but may be useful for reducing code
>> size
>> > in production builds, much like defining NDEBUG. The compiler will still
>> > optimize based on the exception specifications.
>> >
>> > This means that -fno-enforce-eh-specs let's you keep using exceptions.
>> >
>> >
>> > A better alternative to `throw()` combined with `-fno-enforce-eh-specs`
>> is
>> > `noexcept` in C++11. If you throw, you are into undefined behavior land
>> > because there is no runtime check.
>>
>> That was true for a while when the 'noexcept' feature was being
>> designed, but is no longer the case. Just as a 'throw()' exception
>> specification calls 'std::unexpected' when an exception is thrown, a
>> 'noexcept' exception specification calls 'std::terminate'. See C++11
>> [except.spec] p9.
>>
>
> Damned.
>
> Thanks for the update.
>
> Do you think it would make sense to implement the `-fno-enforce-eh-specs`
> flag then ?
>
> -- Matthieu
>
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