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[3/3] kbuild: redefine __FILE__ as relative path from $(srctree) if possible

Message ID 1507885961-12665-4-git-send-email-yamada.masahiro@socionext.com
State Superseded
Headers show
Series kbuild: always use relative path for __FILE__ | expand

Commit Message

Masahiro Yamada Oct. 13, 2017, 9:12 a.m. UTC 
Since Kbuild runs in the objtree, __FILE__ can be a very long path
depending of $(srctree).

If objtree is a child of srctree, the situation is a bit better.
($(srctree) is "..")

For other cases of out-of-tree build, filenames in WARN_ON() etc. are
still an absolute path.  It also means the U-Boot image depends on
where it was built.

Here, the idea is to redefine __FILE__ as the relative path from
$(srctree), but doing so causes a compiler warning:
  warning: "__FILE__" redefined [-Wbuiltin-macro-redefined]

The option -Wno-builtin-macro-redefined can suppress it, but it is
only recognized by GCC 4.4 or newer.  Redefine __FILE__ only when
possible.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

 Makefile | 9 +++++++++
 1 file changed, 9 insertions(+)
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Patch

diff --git a/Makefile b/Makefile
index 888486b..ab7775d 100644
--- a/Makefile
+++ b/Makefile
@@ -1334,6 +1334,15 @@  prepare0: archprepare FORCE
 # All the preparing..
 prepare: prepare0
 
+# If possible, redefne __FILE__ as relative path from $(srctree).
+# $$ is needed to expand the following in submake
+ifeq ($(call cc-option-yn,-Wno-builtin-macro-redefined),y)
+KBUILD_CFLAGS   += -Wno-builtin-macro-redefined \
+		   -D__FILE__=$$(call stringify,$$(src)/$$(notdir $$<))
+endif
+# CAUTION: Do not add any reference to KBUILD_CFLAGS below this line.
+# Any call of cc-option, etc. will fail.
+
 # Generate some files
 # ---------------------------------------------------------------------------