Commit 1eb2e71e authored by Masahiro Yamada's avatar Masahiro Yamada Committed by Tom Rini

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

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's avatarMasahiro Yamada <>
Reviewed-by: Simon Glass's avatarSimon Glass <>
parent fac379e1
......@@ -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_AFLAGS) sets -g, which causes gcc to pass a suitable -g<format>
# option to the assembler.
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