make: Fix makefile depend generation
The main goal of this is to fix "make --question -C cryptoc" behavior
for projects that depend on this library (Chromium EC, Cr50).
Without this fix, when invoking make with the --question flag,
a full build of all *.o was triggered, minus libcryptoc.a.
This was because the "-include $(DEPS)" make step depended on *.d
files. That would then trigger the primary "$(obj)/%.d $(obj)/%.o"
rule, which [yes generated .d files, but] generated the objects.
The following article explains the art of makefile depends quite well:
http://make.mad-scientist.net/papers/advanced-auto-dependency-generation
BUG=none
TEST=make clean; make -q && echo Fail
# No CC builds should occur and no Fail was emitted
# Before this change, the make -q would trigger a build
TEST=make clean; make || echo Fail; make -q || echo Fail
# No Fail should be emitted
TEST=make
touch include/cryptoc/sha.h
make
# See sha.o, hmac.o, and libcryptoc.a being remade
TEST=make
touch include/cryptoc/util.h
make
# See hmac.o, util.o, and libcryptoc.a being remade
TEST=make
mv include/cryptoc/util.h include/cryptoc/utill.h
# Change header reference in util.c and hmac.c
make
# See hmac.o, util.o, and libcryptoc.a being remade
TEST=# Run the following for a few minutes
while true; do \
make clean &>/dev/null; \
make -q && echo Fail; \
make -j &>/dev/null; \
make -q || echo Fail; \
make clean &>/dev/null; \
make -q && echo Fail; \
make &>/dev/null; \
make -q || echo Fail; \
echo -n .; \
done
Change-Id: I1ec8a9acca06d8475011563365b57a16f65b2e84
diff --git a/Makefile b/Makefile
index 863a53b..f0f9ef1 100644
--- a/Makefile
+++ b/Makefile
@@ -46,15 +46,17 @@
# Special target which allows to trigger re-compiling of all sources without
# linking a library.
+.PHONY: objs
objs: $(OBJS)
$(obj):
@echo " MKDIR $(obj)"
$(Q)mkdir -p $(obj)
-$(obj)/%.d $(obj)/%.o: %.c | $(obj)
+$(obj)/%.o: %.c | $(obj)
@echo " CC $(notdir $<)"
- $(Q)$(CC) $(CFLAGS) -c -MMD -MF $(basename $@).d -MT $(basename $@).o \
+ $(Q)$(CC) $(CFLAGS) -c \
+ -MMD -MP -MF $(basename $@).d -MT $(basename $@).o \
-o $(basename $@).o $<
.PHONY: clean
@@ -62,6 +64,6 @@
@echo " RM $(obj)"
$(Q)rm -rf $(obj)
-ifneq ($(MAKECMDGOALS),clean)
+# Don't forget, this include line can trigger builds for the $(DEPS),
+# so do not provide a rule to make %.d.
-include $(DEPS)
-endif
