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kbuild: use -fmacro-prefix-map to make __FILE__ a relative path

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The __FILE__ macro is used everywhere in U-Boot to locate the file
printing the log message, such as WARN_ON(), etc.  If U-Boot is
built out of tree, this can be a long absolute path.

This is because Kbuild runs in the objtree instead of the srctree,
then __FILE__ is expanded to a file path prefixed with $(srctree)/.

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,
more reproducible builds, and smaller image size.

[ Linux commit: a73619a845d5625079cc1b3b820f44c899618388 ]

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
Masahiro Yamada 2018-04-16 13:18:31 +09:00 committed by Tom Rini
parent fac379e1ea
commit 1eb2e71edd
1 changed files with 3 additions and 0 deletions
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3
Makefile
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@ -595,6 +595,9 @@ endif
KBUILD_CFLAGS += $(call cc-option,-fno-stack-protector)
KBUILD_CFLAGS += $(call cc-option,-fno-delete-null-pointer-checks)
# change __FILE__ to the relative path from the srctree
KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
KBUILD_CFLAGS += -g
# $(KBUILD_AFLAGS) sets -g, which causes gcc to pass a suitable -g<format>
# option to the assembler.