path: root/usr
diff options
authorMasahiro Yamada <>2020-04-23 23:23:53 +0900
committerMasahiro Yamada <>2020-05-12 13:28:33 +0900
commit30a7729771731971839cc969d2a321e6ea7a144b (patch)
tree5ecc32acc767d02fde56084c435073be35ab3486 /usr
parent8b59cd81dc5e724eaea283fa6006985891c7bff4 (diff)
kbuild: use -MMD instead of -MD to exclude system headers from dependency
This omits system headers from the generated header dependency. System headers are not updated unless you upgrade the compiler. Nor do they contain CONFIG options, so fixdep does not need to parse them. Having said that, the effect of this optimization will be quite small because the kernel code generally does not include system headers except <stdarg.h>. Host programs include a lot of system headers, but there are not so many in the kernel tree. At first, keeping system headers in .*.cmd files might be useful to detect the compiler update, but there is no guarantee that <stdarg.h> is included from every file. So, I implemented a more reliable way in the previous commit. Signed-off-by: Masahiro Yamada <>
Diffstat (limited to 'usr')
1 files changed, 1 insertions, 1 deletions
diff --git a/usr/include/Makefile b/usr/include/Makefile
index b568a95d1f62..5a7ee3e5ed86 100644
--- a/usr/include/Makefile
+++ b/usr/include/Makefile
@@ -8,7 +8,7 @@
# We cannot go as far as adding -Wpedantic since it emits too many warnings.
UAPI_CFLAGS := -std=c90 -Wall -Werror=implicit-function-declaration
-override c_flags = $(UAPI_CFLAGS) -Wp,-MD,$(depfile) -I$(objtree)/usr/include
+override c_flags = $(UAPI_CFLAGS) -Wp,-MMD,$(depfile) -I$(objtree)/usr/include
# The following are excluded for now because they fail to build.