On 11/11/2016, 03:00 PM, Jiri Olsa wrote: > On Fri, Nov 11, 2016 at 12:23:25PM +0100, Jiri Slaby wrote: >> Hi, >> >> I am trying a new gcc with new warnings enabled: >> >> make O=../a/gcc7/ CC='gcc-7' V=1 kernel/exit.o >> EXTRA_CFLAGS='-Wimplicit-fallthrough=3' >> >> But the build fails when building under tools/: >> ... >> make -f /home/latest/linux/tools/build/Makefile.build dir=. obj=fixdep >> gcc >> -Wp,-MD,/home/latest/a/gcc7/tools/objtool/.exec-cmd.o.d,-MT,/home/latest/a/gcc7/tools/objtool/exec-cmd.o >> -Wbad-function-cast -Wdeclaration-after-statement -Wformat-security >> -Wformat-y2k -Winit-self -Wmissing-declarations -Wmissing-prototypes >> -Wnested-externs -Wno-system-headers -Wold-style-definition -Wpacked >> -Wredundant-decls -Wshadow -Wstrict-aliasing=3 -Wstrict-prototypes >> -Wswitch-default -Wswitch-enum -Wundef -Wwrite-strings -Wformat >> -Wimplicit-fallthrough=3 -ggdb3 -Wall -Wextra -std=gnu99 -O6 >> -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fPIC -Werror >> -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -D_GNU_SOURCE >> -I/home/latest/linux/tools/include/ -I/home/latest/linux/include/uapi >> -I/home/latest/linux/include -D"BUILD_STR(s)=#s" -c -o >> /home/latest/a/gcc7/tools/objtool/exec-cmd.o exec-cmd.c >> gcc: error: unrecognized command line option ‘-Wimplicit-fallthrough=3’; >> did you mean ‘-Wno-fallthrough’? >> >> >> Apparently, CC is not respected for tools/ dir. >> >> Well, it is used (tools/build/Makefile.build): >> # Compile command >> quiet_cmd_cc_o_c = CC $@ >> cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $< >> >> >> But I don't know why CFLAGS propagate from Makefile to tools/, but CC >> doesn't (both are exported)? Any ideas? > > so the root Makefile assign CC directly: > CC = $(CROSS_COMPILE)gcc > > we are trying to be a little bit smarter in perf > and set it only if it's not set by user > > # Allow setting CC and AR and LD, or setting CROSS_COMPILE as a prefix. > $(call allow-override,CC,$(CROSS_COMPILE)gcc) > $(call allow-override,AR,$(CROSS_COMPILE)ar) > $(call allow-override,LD,$(CROSS_COMPILE)ld) > > I did not check the other tools.. Note that I don't care about tools at all. objtool (see the dump above) is apparently needed to build the kernel proper, so it is built as a part of kernel. BTW shouldn't it use HOSTCC anyway? thanks, -- js suse labs -- 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
