kbuild: resolve symlinks for O= properly
Currently, Kbuild follows the logical chain of directories for the O=
option, just like 'cd' (or 'realpath --logical') does.
Example:
$ mkdir -p /tmp/a /tmp/x/y
$ ln -s /tmp/x/y /tmp/a/b
$ realpath /tmp/a/b/..
/tmp/x
$ realpath --logical /tmp/a/b/..
/tmp/a
$ make O=/tmp/a/b/.. defconfig
make[1]: Entering directory '/tmp/a'
[snip]
make[1]: Leaving directory '/tmp/a'
'make O=/tmp/a/b/.. defconfig' creates the kernel configuration in
/tmp/a instead of /tmp/x despite /tmp/a/b/.. resolves to /tmp/x.
This is because Kbuild internally uses the 'cd ... && pwd' for the
path resolution, but this behavior is not predictable for users.
Additionally, it is not consistent with how the Kbuild handles the
M= option or GNU Make works with 'make -C /tmp/a/b/..'.
Using the physical directory structure for the O= option seems more
reasonable.
The comment says "expand a shell special character '~'", but it has
already been expanded to the home directory in the command line.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>
diff --git a/Makefile b/Makefile
index 5a11804..6204a38 100644
--- a/Makefile
+++ b/Makefile
@@ -190,14 +190,11 @@
endif
ifneq ($(KBUILD_OUTPUT),)
-# Make's built-in functions such as $(abspath ...), $(realpath ...) cannot
-# expand a shell special character '~'. We use a somewhat tedious way here.
-abs_objtree := $(shell mkdir -p $(KBUILD_OUTPUT) && cd $(KBUILD_OUTPUT) && pwd)
-$(if $(abs_objtree),, \
- $(error failed to create output directory "$(KBUILD_OUTPUT)"))
-
+# $(realpath ...) gets empty if the path does not exist. Run 'mkdir -p' first.
+$(shell mkdir -p "$(KBUILD_OUTPUT)")
# $(realpath ...) resolves symlinks
-abs_objtree := $(realpath $(abs_objtree))
+abs_objtree := $(realpath $(KBUILD_OUTPUT))
+$(if $(abs_objtree),,$(error failed to create output directory "$(KBUILD_OUTPUT)"))
endif # ifneq ($(KBUILD_OUTPUT),)
ifneq ($(words $(subst :, ,$(abs_srctree))), 1)
