Hi Nick. 2017-10-01 8:14 GMT+09:00 Nick Desaulniers <nick.desaulniers@xxxxxxxxx>: > On Thu, Sep 28, 2017 at 07:52:35PM +0900, Masahiro Yamada wrote: >> 2017-09-26 11:28 GMT+09:00 Nick Desaulniers <nick.desaulniers@xxxxxxxxx>: >> > HOSTCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 \ >> > + $(call hostcc-option,-fno-delete-null-pointer-checks) \ >> > -fomit-frame-pointer -std=gnu89 $(HOST_LFS_CFLAGS) >> >> You call hostcc-option >> before Kbuild.include is included around line 341. >> >> So, $(call hostcc-option, ...) returns always an empty string here >> whether the compiler supports the option or not. > > So calling a yet-to-be defined variable results in an empty string > rather than a loud failure? Chalk that up there with language features > no one ever asked for. That kind of implicit conversion gets languages > like JavaScript (with its loose type system, not that C is without its > own implicit type conversions/promotions) in a lot of hot water. > > If that's the case, why are includes not at the top of Makefiles, if > silent failure is a possibility? Is there a reason the include is so > far into the Makefile? Kbuild.include depends on some other variables. You can not include it at the top of the Makefile. > Is your sugguestion to raise the include or lower the HOSTCFLAGS > definition? In this case, you do not need to move any of them. -fno-delete-null-pointer-checks has never enabled for host-tools before. Just remove it to keep the current behavior. >> > -ifeq ($(shell $(HOSTCC) -v 2>&1 | grep -c "clang version"), 1) >> > -HOSTCFLAGS += -Wno-unused-value -Wno-unused-parameter \ >> > - -Wno-missing-field-initializers -fno-delete-null-pointer-checks >> > -endif >> >> The logic is very strange in the first place. >> >> Even very old GCC supports -fno-delete-null-pointer-checks, >> but clang does not. >> >> Here, -fno-delete-null-pointer-checks is added only when >> we are using clang for HOSTCC. This is opposite. >> >> I guess we can remove all of them >> unless somebody can explain the rationale. > > +llvm-linux > > I suppose maybe different ARCH's have different host binaries made > during the build? I tested x86_64 and arm64. The commit message that > added them missed any context or justification. According to http://llvm.linuxfoundation.org/index.php/Main_Page llvm-linux was only successful for x86, arm(64) at that time. If you tested x86_64 and arm64, and saw no problem, it is fine. -- Best Regards Masahiro Yamada -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
