Hi,
The GNU standards [1] say:
"Try to make the build and installation targets, at least (and all their
subtargets) work correctly with a parallel make."
But supporting parallel requires, in some cases, mechanical changes to a
Makefile. How about if GNU make was improved to not require me to make these
changes?
Namely, consider this Makefile:
===================================================
all : copy1 copy2 copy3 copy4
copy1 copy2 copy3 copy4: Makefile
install -c -m 644 Makefile copy1
install -c -m 644 Makefile copy2
install -c -m 644 Makefile copy3
install -c -m 644 Makefile copy4
===================================================
Observe:
* "rm -f copy?; make" works fine.
* "rm -f copy?; make -j8" occasionally fails:
$ rm -f copy? ; make -j8
install -c -m 644 Makefile copy1
install -c -m 644 Makefile copy1
install -c -m 644 Makefile copy1
install -c -m 644 Makefile copy1
install -c -m 644 Makefile copy2
install -c -m 644 Makefile copy2
install -c -m 644 Makefile copy2
install -c -m 644 Makefile copy2
install: cannot change permissions of 'copy2': No such file or directory
install -c -m 644 Makefile copy3
Makefile:4: recipe for target 'copy2' failed
make: *** [copy2] Error 1
make: *** Waiting for unfinished jobs....
install -c -m 644 Makefile copy3
install -c -m 644 Makefile copy3
install -c -m 644 Makefile copy4
install -c -m 644 Makefile copy4
install -c -m 644 Makefile copy4
The workaround is to introduce an intermediate target:
===================================================
all : copy1 copy2 copy3 copy4
copy1 copy2 copy3 copy4: install-copies
.PHONY: install-copies
install-copies: Makefile
install -c -m 644 Makefile copy1
install -c -m 644 Makefile copy2
install -c -m 644 Makefile copy3
install -c -m 644 Makefile copy4
===================================================
This is tedious, mechanical work. Couldn't GNU make implement the workaround
by itself? Namely, when during a parallel make, it encounters a rule
target1 ... targetN : dependencies
STATEMENTS
and none of the statements depends on the precise target ($@ or similar),
it should transform that to the form
target1 ... targetN : intermediate_target
.PHONY: intermediate_target
intermediate_target: dependencies
STATEMENTS
internally.
$ make --version
GNU Make 4.1
Best regards,
Bruno
[1] https://www.gnu.org/prep/standards/html_node/Makefile-Basics.html
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