[Minios-devel] [UNIKRAFT PATCH] build: fix uncontional full recompilation

[Yuri Volchkov <yuri.volchkov@xxxxxxxxx>]

Files app.uk and elib.uk are regenerated always, but config.h depends
on both of them. And because config.h is included by EVERY file in the
unikraft (and apps), this forces a full recompilation every time one
runs make.

Let's do not touch mentioned files at first, and generate app.uk.new
and elib.uk.new instead. Then compare them with what we have from last
build (app.uk and elib.uk). If they do not match copy *.new to the
final destination.

Signed-off-by: Yuri Volchkov <yuri.volchkov@xxxxxxxxx>
---
 Makefile | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/Makefile b/Makefile
index 7a34396..b177bff 100644
--- a/Makefile
+++ b/Makefile
@@ -541,7 +541,10 @@ HOSTCFLAGS = $(CFLAGS_FOR_BUILD)
 export HOSTCFLAGS
 
 # auto-generated KConfig files for including external app
-$(KCONFIG_APP_IN):
+$(KCONFIG_APP_IN) $(KCONFIG_ELIB_IN): %: %.new
+       @cmp -s $^ $@; if [ $$? -ne 0 ]; then cp $^ $@; fi
+
+$(KCONFIG_APP_IN).new:
        @echo '# external application' > $@
 ifneq ($(UK_BASE),$(UK_APP))
        @echo 'source "$(APP_DIR)/Config.uk"' >> $@
@@ -550,14 +553,14 @@ else
 endif
 
 # auto-generated KConfig files for including external libraries
-$(KCONFIG_ELIB_IN):
+$(KCONFIG_ELIB_IN).new:
        @echo '# external libraries' > $@
        @$(foreach E,$(ELIB_DIR), \
                echo 'source "$(E)/Config.uk"' >> $@; \
        )
 
 # enforce execution
-.PHONY: $(KCONFIG_APP_IN) $(KCONFIG_ELIB_IN)
+.PHONY: $(KCONFIG_APP_IN).new $(KCONFIG_ELIB_IN).new
 
 $(KCONFIG_DIR)/%onf:
        mkdir -p $(@D)/lxdialog
-- 
2.16.1


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