=== b1.log ===
Warning: Object directory not changed from original /usr/src/sys/bus/iicbus/iicbus
cc  -O2 -pipe   -D_KERNEL -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes  -Wmissing-prototypes -Wpointer-arith -Wcast-qual  -Wold-style-definition -Wmissing-include-dirs  -Wno-pointer-sign -Winit-self -Wundef -Wno-unused-but-set-variable -std=gnu11 -Werror -DKLD_MODULE -nostdinc  -I. -Idragonfly -I/usr/src/sys/bus/iicbus/iicbus/forwarder_x86_64/include -Idragonfly/../include  -Wold-style-declaration -fno-common -ffreestanding -fno-stack-protector -fno-strict-aliasing -fno-strict-overflow -fno-asynchronous-unwind-tables -fno-omit-frame-pointer -mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float -mno-fp-ret-in-387 -mindirect-branch=thunk-inline   -c iicbus_if.c
cc  -O2 -pipe   -D_KERNEL -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes  -Wmissing-prototypes -Wpointer-arith -Wcast-qual  -Wold-style-definition -Wmissing-include-dirs  -Wno-pointer-sign -Winit-self -Wundef -Wno-unused-but-set-variable -std=gnu11 -Werror -DKLD_MODULE -nostdinc  -I. -Idragonfly -I/usr/src/sys/bus/iicbus/iicbus/forwarder_x86_64/include -Idragonfly/../include  -Wold-style-declaration -fno-common -ffreestanding -fno-stack-protector -fno-strict-aliasing -fno-strict-overflow -fno-asynchronous-unwind-tables -fno-omit-frame-pointer -mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float -mno-fp-ret-in-387 -mindirect-branch=thunk-inline   -c /usr/src/sys/bus/iicbus/iicbus/../iiconf.c
cc  -O2 -pipe   -D_KERNEL -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes  -Wmissing-prototypes -Wpointer-arith -Wcast-qual  -Wold-style-definition -Wmissing-include-dirs  -Wno-pointer-sign -Winit-self -Wundef -Wno-unused-but-set-variable -std=gnu11 -Werror -DKLD_MODULE -nostdinc  -I. -Idragonfly -I/usr/src/sys/bus/iicbus/iicbus/forwarder_x86_64/include -Idragonfly/../include  -Wold-style-declaration -fno-common -ffreestanding -fno-stack-protector -fno-strict-aliasing -fno-strict-overflow -fno-asynchronous-unwind-tables -fno-omit-frame-pointer -mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float -mno-fp-ret-in-387 -mindirect-branch=thunk-inline   -c /usr/src/sys/bus/iicbus/iicbus/../iicbus.c
cc -Wl,--build-id=sha1 -nostdlib -Wl,--hash-style=sysv   -r -Wl,-d -o iicbus.ko iicbus_if.o iiconf.o iicbus.o
=== b2.log ===
Warning: Object directory not changed from original /usr/src/sys/bus/iicbus/iicsmb
cc  -O2 -pipe   -D_KERNEL -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes  -Wmissing-prototypes -Wpointer-arith -Wcast-qual  -Wold-style-definition -Wmissing-include-dirs  -Wno-pointer-sign -Winit-self -Wundef -Wno-unused-but-set-variable -std=gnu11 -Werror -DKLD_MODULE -nostdinc  -I. -Idragonfly -I/usr/src/sys/bus/iicbus/iicsmb/forwarder_x86_64/include -Idragonfly/../include  -Wold-style-declaration -fno-common -ffreestanding -fno-stack-protector -fno-strict-aliasing -fno-strict-overflow -fno-asynchronous-unwind-tables -fno-omit-frame-pointer -mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float -mno-fp-ret-in-387 -mindirect-branch=thunk-inline   -c /usr/src/sys/bus/iicbus/iicsmb/../iicsmb.c
cc -Wl,--build-id=sha1 -nostdlib -Wl,--hash-style=sysv   -r -Wl,-d -o iicsmb.ko iicsmb.o
=== b3.log ===
Warning: Object directory not changed from original /usr/src/sys/dev/smbus/smb
cc  -O2 -pipe   -D_KERNEL -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes  -Wmissing-prototypes -Wpointer-arith -Wcast-qual  -Wold-style-definition -Wmissing-include-dirs  -Wno-pointer-sign -Winit-self -Wundef -Wno-unused-but-set-variable -std=gnu11 -Werror -DKLD_MODULE -nostdinc  -I. -Idragonfly -I/usr/src/sys/dev/smbus/smb/forwarder_x86_64/include -Idragonfly/../include  -Wold-style-declaration -fno-common -ffreestanding -fno-stack-protector -fno-strict-aliasing -fno-strict-overflow -fno-asynchronous-unwind-tables -fno-omit-frame-pointer -mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float -mno-fp-ret-in-387 -mindirect-branch=thunk-inline   -c smb.c
cc -Wl,--build-id=sha1 -nostdlib -Wl,--hash-style=sysv   -r -Wl,-d -o smb.ko smb.o
=== b4.log ===
Warning: Object directory not changed from original /usr/src/sys/bus/iicbus/df5521
cc  -O2 -pipe   -D_KERNEL -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes  -Wmissing-prototypes -Wpointer-arith -Wcast-qual  -Wold-style-definition -Wmissing-include-dirs  -Wno-pointer-sign -Winit-self -Wundef -Wno-unused-but-set-variable -std=gnu11 -Werror -DKLD_MODULE -nostdinc  -I. -Idragonfly -I/usr/src/sys/bus/iicbus/df5521/forwarder_x86_64/include -Idragonfly/../include  -Wold-style-declaration -fno-common -ffreestanding -fno-stack-protector -fno-strict-aliasing -fno-strict-overflow -fno-asynchronous-unwind-tables -fno-omit-frame-pointer -mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float -mno-fp-ret-in-387 -mindirect-branch=thunk-inline   -c df5521_rig.c
cc -Wl,--build-id=sha1 -nostdlib -Wl,--hash-style=sysv   -r -Wl,-d -o df5521_rig.ko df5521_rig.o

[rig build — first-time build, from session]
# cd /usr/src/sys/bus/iicbus/df5521 && make
cc  -O2 -pipe -D_KERNEL ... -Werror -DKLD_MODULE ... -c df5521_rig.c
cc -Wl,--build-id=sha1 -nostdlib -Wl,--hash-style=sysv -r -Wl,-d -o df5521_rig.ko df5521_rig.o
# cc -O -o /root/df5521_poc /root/df5521_poc.c
(userland PoC: no warnings)
All module builds above are -Werror clean; .ko files linked:
-rw-r--r-- 1 root wheel 11592 iicbus.ko
-rw-r--r-- 1 root wheel 13480 iicsmb.ko
-rw-r--r-- 1 root wheel 10728 smb.ko