| Message ID | 1522383326-3880-1-git-send-email-yamada.masahiro@socionext.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
2018-03-30 13:15 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>: > 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> > --- > > I tested this on GCC 8. > (not released yet, but you can get the source code from the trunk.) Applied to linux-kbuild.
diff --git a/Makefile b/Makefile index 7ba478a..83d25c9 100644 --- a/Makefile +++ b/Makefile @@ -856,6 +856,9 @@ 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)
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; $(srctree) becomes ".." if the objtree is a child of the srctree. For other cases of out-of-tree build, __FILE__ is still the absolute path. It also means the kernel image depends on where it was built. A brand-new option from GCC, -fmacro-prefix-map, solves this problem. If your compiler supports it, __FILE__ is the relative path from the srctree regardless of O= option. This provides more readable log and more reproducible builds. Please note __FILE__ is always an absolute path for external modules. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> --- I tested this on GCC 8. (not released yet, but you can get the source code from the trunk.) Changes in v3: - It is harmless to always set this option. Remove ifneq ifneq ($(KBUILD_SRC),) Changes in v2: - Comment-in the ifeq Makefile | 3 +++ 1 file changed, 3 insertions(+)