Hi Josh, with your work on objtool and the upcoming implementation of -fno-delete-null-pointer-checks (https://reviews.llvm.org/D47894, https://reviews.llvm.org/D47895) in clang most objtool warnings for clang builds will be fixed.
However even with -fno-delete-null-pointer-checks we currently still get a warning about native_machine_emergency_restart(): arch/x86/kernel/reboot.o: warning: objtool: native_machine_emergency_restart() falls through to next function machine_power_off() This only occurs when building with -Oz. One of our compiler engineers looked into this, LLVM optimizes the return statement away since the function has an endless loop, and actually never returns. Is there a way to tell objtool that the function is not expected to return (I tried the attribute __noreturn, but it doesn't make a difference), or do we have to tell clang to restrain from optimizing returns out? To repro: git checkout v4.16 make CC=clang defconfig echo "CONFIG_CC_OPTIMIZE_FOR_SIZE=y" >> .config make CC=clang arch/x86/kernel/reboot.o Thanks Matthias