Strict-aliasing rule breaking

[Lorenzo Bertini]

Dear developers,
as discussed here (https://bugs.gentoo.org/858377), gperf cannot be
build with "-Werror=strict-aliasing". This is what GCC gives me:

In file included from ./keyword-list.h:78,
                 from ./keyword-list.cc:22:
./keyword-list.icc: In member function ‘KeywordExt_List*&
KeywordExt_List::rest()’:
./keyword-list.icc:50:11: error: dereferencing type-punned pointer
will break strict-aliasing rules [-Werror=strict-aliasing]
   50 |   return *reinterpret_cast<KeywordExt_List**>(&_cdr);
      |           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from ./keyword-list.h:78,
                 from ./output.h:27,
                 from ./output.cc:22:

Gentoo recommends "-Werror=strict-aliasing" as part of a project that
allows to build every package with LTO. As more distributions are
transitioning to LTO build, it might be beneficial to not have this
warning.

Thank you for your attention,
best wishes and happy holidays!

Lorenzo