Bug#812047: grub2: FTBFS with GCC 6: '-Wunreachable-code' is not an option

[Martin Michlmayr]

Package: grub2
Version: 2.02~beta2-33
Severity: important
User: debian-gcc at lists.debian.org
Usertags: ftbfs-gcc-6

This package fails to build with GCC 6.  GCC 6 has not been released
yet, but it's expected that GCC 6 will become the default compiler for
stretch.

Note that only the first error is reported; there might be more.  You
can find a snapshot of GCC 6 in experimental.  To build with GCC 6,
you can set CC=gcc-6 CXX=g++-6 explicitly.

You may be able to find out more about this issue at
https://gcc.gnu.org/gcc-6/changes.html

> sbuild (Debian sbuild) 0.67.0 (26 Dec 2015) on dl580gen9-02.hlinux
...
> -Wcast-align  -Wextra -Wattributes -Wendif-labels -Winit-self -Wint-to-pointer-cast -Winvalid-pch -Wmissing-field-initializers -Wnonnull -Woverflow -Wvla -Wpointer-to-int-cast -Wstrict-aliasing -Wvariadic-macros -Wvolatile-register-var -Wpointer-sign -Wmissing-include-dirs -Wmissing-prototypes -Wmissing-declarations -Wformat=2 -Werror  -fno-builtin -Wno-undef  -c -o grub-core/fs/libgrubmods_a-ext2.o `test -f 'grub-core/fs/ext2.c' || echo '../../'`grub-core/fs/ext2.c
> ../../grub-core/lib/pbkdf2.c:34:32: error: '-Wunreachable-code' is not an option that controls warnings [-Werror=pragmas]
>  #pragma GCC diagnostic ignored "-Wunreachable-code"
>                                 ^~~~~~~~~~~~~~~~~~~~