On Thu, May 05, 2022 at 04:22:43PM +0900 Masahiro Yamada wrote: > Kbuild runs at the top of objtree instead of changing the working > directory to subdirectories. I think this design is nice overall but > some commands have a scapability issue. > > The build command of built-in.a is one of them whose length scales with: > > O(D * N) > > Here, D is the length of the directory path (i.e. $(obj)/ prefix), > N is the number of objects in the Makefile, O() is the big O notation. > > The deeper directory the Makefile directory is located, the more easily > it will hit the too long argument error. > > We can make it better. Trim the $(obj)/ by Make's builtin function, and > restore it by a shell command (sed). > > With this, the command length scales with: > > O(D + N) > > In-tree modules still have some room to the limit (ARG_MAX=2097152), > but this is more future-proof for big modules in a deep directory. > > For example, you can build i915 as builtin (CONFIG_DRM_I915=y) and > compare drivers/gpu/drm/i915/.built-in.a.cmd with/without this commit. > > Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> > --- > > (no changes since v2) > > Changes in v2: > - New patch > > scripts/Makefile.build | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/scripts/Makefile.build b/scripts/Makefile.build > index 0436ff94800e..cea48762299c 100644 > --- a/scripts/Makefile.build > +++ b/scripts/Makefile.build > @@ -370,7 +370,10 @@ $(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ; > # > > quiet_cmd_ar_builtin = AR $@ > - cmd_ar_builtin = rm -f $@; $(AR) cDPrST $@ $(real-prereqs) > + cmd_ar_builtin = rm -f $@; \ > + echo $(patsubst $(obj)/%,%,$(real-prereqs)) | \ > + sed -E 's:([^ ]+):$(obj)/\1:g' | \ > + xargs $(AR) cDPrST $@ > > $(obj)/built-in.a: $(real-obj-y) FORCE > $(call if_changed,ar_builtin) > -- > 2.32.0 Reviewed-by: Nicolas Schier <nicolas@xxxxxxxxx>
