CODEWITHSUNDEEP
makefilegnuprerequisites
Banyoghurt
Banyoghurt

Reputation: 315

Make: recipe is run, even if the prerequisite exists

i'm having trouble understanding why Make will run the "lib"-recipe even if the file already exists. Shouldn't it be ignored as long "$(LIBBIN)" is not in .PHONY ?

Here is an extract from the Makefile in question (ts=2, see "TODO").

.PHONY: all clean default apps lib examples

default: lib

all: apps lib examples

apps: $(APPBINS)

lib: $(LIBBIN)

examples: $(EXBINS)

$(LIBBIN): % : %.$(VERSION)
# TODO -f should really not be necessary. why is the recipe run, when the file exists?
  ln -sf $^ $@

$(LIBBIN).$(VERSION): $(LIBOBJECTS) | $(LIBOUTDIR)
  $(CC) $^ -o $@ $(LIBLDFLAGS)
  chmod 755 $@

i was hoping one of you gurus knows the answer ;-)

kind regards, yogo1212

EDIT: maybe i should say, that i've already tried to make the prereqs. of lib and all order-only. There was no visible effect.

EDIT2: turns out that this works indeed. the link file seemed to have had a timestamp that was off by a minute and make was confused. the phenomenon went away after re-creating the folder structure and restarting.

Upvotes: 1

Views: 252

Answers (1)

MadScientist
MadScientist

Reputation: 101111

The makefile part you've given is correct and works for me, after I simplified it due to missing details in your example. So, your example is not accurately reflecting your situation. Please try to provide a SSCCE

$ cat Makefile
LIBBIN = /tmp/foo
VERSION = 1.0

lib: $(LIBBIN)

$(LIBBIN): % : %.$(VERSION)
        ln -s $^ $@

$(LIBBIN).$(VERSION): $(LIBOBJECTS) | $(LIBOUTDIR)
        touch $@

$ make
touch /tmp/foo.1.0
ln -s /tmp/foo.1.0 /tmp/foo

$ make -f /tmp/x3.mk 
make: Nothing to be done for `lib'.

Upvotes: 1

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