Messages in this thread Patch in this message | | | From | Rasmus Villemoes <> | Subject | [PATCH 3/3] fixdep: do not ignore kconfig.h | Date | Wed, 28 Feb 2018 20:17:37 +0100 |
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kconfig.h was excluded from consideration by fixdep by 6a5be57f0f00 (fixdep: fix extraneous dependencies) to avoid some false positive hits
(1) include/config/.h (2) include/config/h.h (3) include/config/foo.h
(1) occurred because kconfig.h contains the string CONFIG_ in a comment. However, since dee81e988674 (fixdep: faster CONFIG_ search), we have a check that the part after CONFIG_ is non-empty, so this does not happen anymore (and CONFIG_ appears by itself elsewhere, so that check is worthwhile).
(2) comes from the include guard, __LINUX_KCONFIG_H. But with the previous patch, we no longer match that either.
That leaves (3), which amounts to one [1] false dependency (aka stat() call done by make), which I think we can live with:
We've already had one case [2] where the lack of include/linux/kconfig.h in the .o.cmd file caused a missing rebuild, and while I originally thought we should just put kconfig.h in the dependency list without parsing it for the CONFIG_ pattern, we actually do have some real CONFIG_ symbols mentioned in it, and one can imagine some translation unit that just does '#ifdef __BIG_ENDIAN' but doesn't through some other header actually depend on CONFIG_CPU_BIG_ENDIAN - so changing the target endianness could end up rebuilding the world, minus that small TU. Quoting Linus,
... when missing dependencies cause a missed re-compile, the resulting bugs can be _really_ subtle.
[1] well, two, we now also have CONFIG_BOOGER/booger.h - we could change that to FOO if we care
[2] https://lkml.org/lkml/2018/2/22/838
Cc: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> --- scripts/basic/fixdep.c | 1 - 1 file changed, 1 deletion(-)
diff --git a/scripts/basic/fixdep.c b/scripts/basic/fixdep.c index 1b21870d6e7f..449b68c4c90c 100644 --- a/scripts/basic/fixdep.c +++ b/scripts/basic/fixdep.c @@ -283,7 +283,6 @@ static int is_ignored_file(const char *s, int len) { return str_ends_with(s, len, "include/generated/autoconf.h") || str_ends_with(s, len, "include/generated/autoksyms.h") || - str_ends_with(s, len, "include/linux/kconfig.h") || str_ends_with(s, len, ".ver"); } -- 2.15.1
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