From 5d790e3f528808733676215e4c1040798223f1c7 Mon Sep 17 00:00:00 2001 From: Nico Huber Date: Fri, 17 Aug 2018 17:29:14 +0200 Subject: 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 Reviewed-on: https://review.coreboot.org/28197 Tested-by: build bot (Jenkins) Reviewed-by: Patrick Rudolph --- Makefile.inc | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) (limited to 'Makefile.inc') 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) -- cgit v1.2.3