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author | Masahiro Yamada <yamada.masahiro@socionext.com> | 2018-03-30 07:15:26 +0300 |
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committer | Masahiro Yamada <yamada.masahiro@socionext.com> | 2018-04-07 13:04:02 +0300 |
commit | a73619a845d5625079cc1b3b820f44c899618388 (patch) | |
tree | 18ba6bd224aa6e2f7475d2675b292d2dbdf29728 /Makefile | |
parent | 54a702f70589926acf687f0cd5df24d07230c80e (diff) |
kbuild: use -fmacro-prefix-map to make __FILE__ a relative path
The __FILE__ macro is used everywhere in the kernel to locate the file
printing the log message, such as WARN_ON(), etc. If the kernel is
built out of tree, this can be a long absolute path, like this:
WARNING: CPU: 1 PID: 1 at /path/to/build/directory/arch/arm64/kernel/foo.c:...
This is because Kbuild runs in the objtree instead of the srctree,
then __FILE__ is expanded to a file path prefixed with $(srctree)/.
Commit 9da0763bdd82 ("kbuild: Use relative path when building in a
subdir of the source tree") improved this to some extent; $(srctree)
becomes ".." if the objtree is a child of the srctree.
For other cases of out-of-tree build, __FILE__ is still the absolute
path. It also means the kernel image depends on where it was built.
A brand-new option from GCC, -fmacro-prefix-map, solves this problem.
If your compiler supports it, __FILE__ is the relative path from the
srctree regardless of O= option. This provides more readable log and
more reproducible builds.
Please note __FILE__ is always an absolute path for external modules.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Diffstat (limited to 'Makefile')
-rw-r--r-- | Makefile | 3 |
1 files changed, 3 insertions, 0 deletions
@@ -846,6 +846,9 @@ KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types) # Require designated initializers for all marked structures KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init) +# change __FILE__ to the relative path from the srctree +KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=) + # use the deterministic mode of AR if available KBUILD_ARFLAGS := $(call ar-option,D) |