如何重新启动GNU make（不引起错误）

Question

I need to restart the make process in case some intermediate target gets (re)build.

This is the case when a PIP requirements file gets (re)compiled, because the checksum of the resulting file is used in the path to the virtualenv that is used in the Makefile. If the requirements file gets updated, the same $(MAKECMDGOALS) should get rebuild from the beginning.

I have come up with the following, but this requires to make the outer/inital make process fail ( exit 1 ), which I would like to avoid.

foo:
    echo "foo"

    # Need to restart make if this has been used as intermediate target.
    if [ $(MAKECMDGOALS) != "$@" ]; then \
        echo "Restarting make..."; \
        touch $@; \
        $(MAKE) $(MAKECMDGOALS); \
        exit 1; \
    fi

bar: foo
    echo "bar"

.PHONY: bar

Answer 1

A makefile on the lines below might fit the bill. bar and baz are goals that will be sabotaged if they intermediately make foo (aka tricky goals). There's no restarting involved: instead, it is arranged that the tricky goals are only made by a fresh $(MAKE) , after the top make has ensured foo is up-to-date.

.phony: all clean

tricky = bar baz

all:
    $(MAKE) $(tricky)

foo:
    echo "foo"
    touch $@

clean:
    rm -f foo

ifndef simple
tricky_goals = $(filter $(tricky),$(MAKECMDGOALS))
ifneq ($(tricky_goals),)
$(tricky_goals): foo
    $(MAKE) simple=y $@
endif

else # ifndef simple
# All tricky goals follow...

bar: foo
    echo "bar"

baz: foo
    echo "baz"

endif # ifndef simple

The behaviour depends on whether the variable simple is defined, which by default it is not.

If simple is defined then the goals, whatever they are, will be made the obvious way - the way they'd be made if it weren't for the foo pitfall.

If simple is undefined then tricky_goals becomes the tricky members $(MAKECMDGOALS) . If $(tricky_goals) is empty there is nothing tricky to do. Otherwise the target list $(tricky_goals) becomes dependent on foo . So if foo is out-of-date, it gets made now. Finally each tricky goal is made by calling a simple $(MAKE) for it, in which foo will be up-todate. Any non-tricky goals will be made the simple way.

I've included all and clean goals for completeness. Note that all needs coded to go the tricky way.