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Even though we do have a dependency chain back to each of the kconfig
base and fragment files:
$$($(2)_DIR)/.config: $$($(2)_KCONFIG_FILE) $$($(2)_KCONFIG_FRAGMENT_FILES)
we can't rely on it to ensure they are all present, because they all have
this rule:
$$($(2)_KCONFIG_FILE) $$($(2)_KCONFIG_FRAGMENT_FILES): | $(1)-patch
but since this rule has no prerequisite (only build-order, but that does
not count in this case) and no recipe, make will believe each missing
file to be a PHONY target, and will always run targets that depend on
it:
https://www.gnu.org/software/make/manual/make.html#Force-Targets
So, that means a missing kconfig base or fragment file would always
cause the rule to generate .config to be run at each invocation, which
in turn would cause a rebuild of the kernel, which is clearly not what
we want.
Since this is expected make behaviour, we can well end up with a missing
Kconfig base or fragment. To avoid continuously rebuilding the kernel in
that case, we must check those files exist by ourselves, and error out
if any one of them is missing.
One would expect we check for them right in their dependency rule, like
so:
$$($(2)_KCONFIG_FILE) $$($(2)_KCONFIG_FRAGMENT_FILES): | $(1)-patch
[ -f $(@) ] || {echo Missing $(@) >&2; exit 1; }
but that does not work, as only the first target is tested for. That
check msut be turned into a loop explicitly testing all files, like so:
$$($(2)_KCONFIG_FILE) $$($(2)_KCONFIG_FRAGMENT_FILES): | $(1)-patch
for f in $$($(2)_KCONFIG_FILE) $$($(2)_KCONFIG_FRAGMENT_FILES); do \
[ -f $(@) ] || {echo Missing $$$${f} >&2; exit 1; }; \
done
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Floris Bos <bos@je-eigen-domein.nl>
Cc: Thomas De Schampheleire <patrickdepinguin@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Buildroot is a simple, efficient and easy-to-use tool to generate embedded Linux systems through cross-compilation. The documentation can be found in docs/manual. You can generate a text document with 'make manual-text' and read output/docs/manual/manual.text. Online documentation can be found at http://buildroot.org/docs.html To build and use the buildroot stuff, do the following: 1) run 'make menuconfig' 2) select the target architecture and the packages you wish to compile 3) run 'make' 4) wait while it compiles 5) find the kernel, bootloader, root filesystem, etc. in output/images You do not need to be root to build or run buildroot. Have fun! Buildroot comes with a basic configuration for a number of boards. Run 'make list-defconfigs' to view the list of provided configurations. Please feed suggestions, bug reports, insults, and bribes back to the buildroot mailing list: buildroot@buildroot.org You can also find us on #buildroot on Freenode IRC.