On Sun, 9 Jul 2017 09:55:22 -0700 Vinnie Falco via Boost <boost@lists.boost.org> wrote: VFvB> 1. The one in <beast/zlib/*> is a header-only port of zlib to VFvB> modern-ish C++11. There is a warning "‘*((void*)& old_flush +4)’ may ... VFvB> For #1 The variable is not used uninitialized, I believe it is a false VFvB> positive cause by the implementation of boost::optional. I have spent VFvB> a lot of time trying to fix this, to no avail - if someone smarter VFvB> than me can offer a patch I would be grateful. There is a workaround mentioned at http://www.boost.org/doc/libs/1_64_0/libs/optional/doc/html/boost_optional/t... Otherwise you can just use gcc pragmas to suppress this warning locally, I don't think there is anything else to do (FWIW this issue is tracked in https://svn.boost.org/trac10/ticket/12513) Regards, VZ