[Bug bootstrap/66448] [6 Regression] Bootstrap fails on darwin after r224161

["aldyh at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66448

Aldy Hernandez <aldyh at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org

--- Comment #2 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---

> 2. Once (1) is fixed, bootstrap then fails with:
> 
> /GCC/gcc-trunk/gcc/ipa-pure-const.c:1640:1: error:
> â{anonymous}::pass_ipa_pure_const::pass_ipa_pure_const(gcc::context*)â
> defined but not used [-Werror=unused-function]
>  pass_ipa_pure_const::
> 
> A --disable-werror boostrap completes, but there are a number of
> constructors and destructors that report "declared but not used". AFAICT,
> it's only constructors/destructors.
> 
> This is occurring at stage #2, and I thought maybe that the stage#1 compiler
> could have been mis-compiled by the bootstrap; however, gcc-4.9, 5.1 and
> clang (xcode 5.1.1) bootstraps all give the same result.

Jason, is pass_ipa_pure_const::pass_ipa_pure_const() really declared but not
used?

If so, can we mark it ATTRIBUTE_UNSUED or is there a more generic way of fixing
this?