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authorNico Huber <nico.h@gmx.de>2018-08-17 17:29:14 +0200
committerPatrick Georgi <pgeorgi@google.com>2018-08-20 15:56:29 +0000
commit5d790e3f528808733676215e4c1040798223f1c7 (patch)
tree87653a632a24d7ae3336b1d08f7ef3bdf04faf5b
parent20df17cc65d0fb7c72bd8ffcb5d88447eb6ec8cc (diff)
downloadcoreboot-5d790e3f528808733676215e4c1040798223f1c7.tar.xz
Makefile.inc: Ensure update of build.h
There were so many pitfalls that I wrote my own version of this even- tually. This version is inspired by the procedure of Alex Thiessen[1]. Instead of generating a `build.h` on demand, we always generate a tem- porary version that, if it differs from the current one, is added as a dependency. As we use .SECONDEXPANSION on the prerequisites, special care is taken that we won't generate the file twice. As it would be too late to add the dependency if we'd run `genbuild_h.sh` inside a recipe, we have to run it through the `$(shell)` function. But that brings us to the next issue: The make variables used by `genbuild_h.sh` are not expor- ted to this shell like they would be in a recipe. So we export them manually. We could also make these variables explicit parameters of `genbuild_h.sh` instead. An alternative to always creating the temporary `build.h` would be to add a phony target as dependency instead, and finally calling `genbuild_h.sh` again in case we need an update. But, um, we create so many files anyway... [1] https://review.coreboot.org/25685 Change-Id: I311cf610eabae873c70f2985fc7a09acec8061f0 Signed-off-by: Nico Huber <nico.h@gmx.de> Reviewed-on: https://review.coreboot.org/28197 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Patrick Rudolph <siro@das-labor.org>
-rw-r--r--Makefile.inc21
1 files changed, 17 insertions, 4 deletions
diff --git a/Makefile.inc b/Makefile.inc
index 7ce236031e..3840505cd5 100644
--- a/Makefile.inc
+++ b/Makefile.inc
@@ -464,11 +464,24 @@ export $(COREBOOT_EXPORTS)
#######################################################################
# generate build support files
-$(obj)/build.h: .xcompile
+
+build_h := $(obj)/build.h
+
+# We have to manually export variables that `genbuild_h.sh` uses
+# when we call it through the `$(shell)` function. This is fragile
+# but as variables newly added to `genbuild_h.sh` would just not
+# work, we'd notice that instantly at least.
+build_h_exports := BUILD_TIMELESS KERNELVERSION COREBOOT_EXTRA_VERSION
+
+# Report new `build.ht` as dependency if `build.h` differs.
+build_h_check := \
+ export $(foreach exp,$(build_h_exports),$(exp)="$($(exp))"); \
+ util/genbuild_h/genbuild_h.sh >$(build_h)t 2>/dev/null; \
+ cmp -s $(build_h)t $(build_h) >/dev/null 2>&1 || echo $(build_h)t
+
+$(build_h): $$(shell $$(build_h_check))
@printf " GEN build.h\n"
- rm -f $(obj)/build.h
- util/genbuild_h/genbuild_h.sh > $(obj)/build.ht
- mv $(obj)/build.ht $(obj)/build.h
+ mv $< $@
build-dirs:
mkdir -p $(objcbfs) $(objgenerated)