When I looked at
http://releases.llvm.org/7.0.0/tools/clang/docs/ReleaseNotes.html
I found notes about 2 ABI breakages compared to clang 6 and before:
QUOTE
• Clang’s handling of the GCC packed class attribute in C++ has been
fixed to apply only to non-static data members and not to base
This was targeting amd64.
--- if_fxp.o ---
/usr/src/sys/dev/fxp/if_fxp.c:1630:3: error: array index -1 is before the
beginning of the array [-Werror,-Warray-bounds]
cbp->tbd[-1].tb_size = htole32(m->m_pkthdr.tso_segsz << 16);
^~~
/usr/src/sys/dev/fxp/if_fxp
In looking into another report about using devel/amd64-gcc to buld
head I tried a build of -r338675 ( with WERROR= ). It got:
--- kernel.full ---
linking kernel.full
/usr/local/x86_64-unknown-freebsd12.0/bin/ld: warning: -z ifunc-noplt ignored.
ctfmerge -L VERSION -g -o kernel.full ...
text