CODEWITHSUNDEEP
makefilegnu-make
izac89
izac89

Reputation: 3940

Non phony target behaves like a phony target

I am working on a boot project. In my boot root directory there is a makefile that contains among other things, the following code which confuse me:

.DEFAULT_GOAL = all

.PHONY: all

all: xboot

xboot: $(TOP_DIR)/boot
    @echo "Building Boot" $(TOP_DIR)
    $(MAKE) -C $(TOP_DIR)/boot/src

Now, the problem is, that any time when this makefile is executed by calling make, the xboot receipt is always running. It seems that this xboot target acts like a phony target. From GNU Documentation regarding phony targets:

Phoniness is not inherited: the prerequisites of a phony target are not themselves phony, unless explicitly declared to be so.

Means that xboot target is not a phony one, but it's receipt is always running. I could not find anywhere an explanation for that.

Project facts- directory $(TOP_DIR)/boot contains sources and headers under $(TOP_DIR)/boot/src and $(TOP_DIR)/boot/include, directory $(TOP_DIR)/boot does not get touched at the build (it is not get updated)

Trying to understand the behavior I played around- I tried touching $(TOP_DIR)/boot, and/or tried touching and creating file xboot file anywhere in the project, but behavior remains the same.

GNU Make 4.1 Built for x86_64-pc-linux-gnu

Upvotes: 0

Views: 130

Answers (1)

levif
levif

Reputation: 2176

make is not always handling folder dependencies the way you expect.

Should use a file dependency inside $(TOP_DIR)/boot like $(TOP_DIR)/boot/.exists or, even better, all your source files with a $(wildcard ...) function.

Like:

xcode: $(widcard $(TOP_DIR)/boot/src/*.c $(TOP_DIR)/boot/src/*.h)

This will cause a rebuild only on code change.

Upvotes: 0

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