On 9/20/22 10:06, Jiri Slaby wrote: > On 19. 07. 22, 11:15, Masahiro Yamada wrote: >> On Tue, Jul 19, 2022 at 5:41 PM Jiri Slaby <jslaby@xxxxxxx> wrote: >>> >>> From: Martin Liska <mliska@xxxxxxx> >>> >>> Prefix command in makefile run in order to preserve access to jobserver. >>> This is needed for gcc at least. >>> >>> Fixes this warning: >>> lto-wrapper: warning: jobserver is not available: ‘--jobserver-auth=’ is not present in ‘MAKEFLAGS’ >> >> >> What is lto-wrapper ? > > lto-wrapper is a part of gcc: > https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/lto-wrapper.cc > > And is invoked during the link of LTO objects (also to link in parallel if jobserver is available). Yes, it's a driver that is invoked by Linker when it decides to use LTO mode in GCC compiler. Later on the lto-wrapper connects to make's jobserver and runs in parallel. Note a recent [1] make implemented named pipes when it comes to communication with jobserver. And thus the '+' won't be needed in the future, but we need it for now. Cheers, Martin [1] https://git.savannah.gnu.org/cgit/make.git/commit/?id=7ad2593b2d2bb5b9332f4444d8bf93ac6f958bc6 > > I am leaving the unanswered questions below for Martin to answer. > >>> Cc: Sedat Dilek <sedat.dilek@xxxxxxxxx> >>> Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx> >>> Cc: Michal Marek <michal.lkml@xxxxxxxxxxx> >>> Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> >>> Fixes: 5d45950dfbb1 (kbuild: move vmlinux.o link to scripts/Makefile.vmlinux_o) >>> Signed-off-by: Martin Liska <mliska@xxxxxxx> >>> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx> >>> --- >>> >>> Notes: >>> [v2] this is new in v2 >>> >>> scripts/Makefile.build | 6 +++--- >>> 1 file changed, 3 insertions(+), 3 deletions(-) >>> >>> diff --git a/scripts/Makefile.build b/scripts/Makefile.build >>> index bb63374fb055..493f3c4e8461 100644 >>> --- a/scripts/Makefile.build >>> +++ b/scripts/Makefile.build >>> @@ -247,8 +247,8 @@ endef >>> >>> # Built-in and composite module parts >>> $(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE >>> - $(call if_changed_rule,cc_o_c) >>> - $(call cmd,force_checksrc) >>> + +$(call if_changed_rule,cc_o_c) >>> + +$(call cmd,force_checksrc) >> >> >> cmd_force_checksrc invokes sparse. >> How is it related to GCC? >> >> >> >> >>> >>> # To make this rule robust against "Argument list too long" error, >>> # ensure to add $(obj)/ prefix by a shell command. >>> @@ -457,7 +457,7 @@ endef >>> $(multi-obj-m): objtool-enabled := $(delay-objtool) >>> $(multi-obj-m): part-of-module := y >>> $(multi-obj-m): %.o: %.mod FORCE >>> - $(call if_changed_rule,ld_multi_m) >>> + +$(call if_changed_rule,ld_multi_m) >>> $(call multi_depend, $(multi-obj-m), .o, -objs -y -m) >> >> >> cmd_ld_multi_m invokes $(LD) directly. >> How is it related to gcc? > > >
