Re: Order-only prerequisites
Henrik Carlqvist wrote:
> On Wed, 07 Jun 2023 08:29:15 +0200
> > As I said, a way to specify in which order recipes are invoked
> > (here, a before b) if they are invoked, without influencing whether
> > they are invoked (only a, only b or a and b, as given on the command
> > line).
>
> So you really don't want any target to depend upon another target? Then why do
> you care about the order? If order is important, what would happen if make is
> run with -j and starts several jobs in parallell?
They should run after each other, as per the manual ("... will be
completed before ...").
Roughly speaking, my project consists of several major parts and I
want to be able to selectively rebuild them. E.g., B does depend on
A, but sometimes I want to only rebuild B even though there were
changes to A, because I don't care about those changes at the moment
and rebuilding A takes a long time.
But when I rebuild both of them, especially when I do a full
rebuild, they should be built in the order of their dependencies, as
usual.
I had hoped that order-only prerequisites would do what I want, but
I see now they don't and I'll have to do it some other way.
(Basically, I'm duplicating the rules, one copy with and one without
dependencies, "all" depends on those with dependencies, but manually
I can use those without.)
Paul Smith wrote:
> The documentation of order-only prequisites says what they're for:
>
> > A normal prerequisite makes two statements: first, it imposes an
> > order in which recipes will be invoked: the recipes for all
> > prerequisites of a target will be completed before the recipe for the
> > target is run. Second, it imposes a dependency relationship: if any
> > prerequisite is newer than the target, then the target is considered
> > out-of-date and must be rebuilt.
> >
> > [Order-only prerequisites] impose a specific ordering on the rules to
> > be invoked _without_ forcing the target to be updated if one of those
> > rules is executed.
>
> Makes treats order-only prereqs identically to "normal" prereqs in
> every way, EXCEPT that at the time where it checks to see whether the
> target needs to be rebuilt it doesn't consider the timestamps of the
> order-only prerequisites. That's all there is.
I still suggest mentioning that they still cause the prerequisites
to be built (when necessary), and I'm still not happy with the
naming. Maybe that's because I'm a mathematician and used to exact
wording, but to me "a b" and "b a" are different orders of the same
set, but "b" and "a b" are not, so they're not about order only.
Re: Order-only prerequisites
On Wed, 2023-06-07 at 04:20 +0200, Frank Heckenbach wrote: > What I want to achieve is that a and b can be made independently, > but when both of them are made, a is always made first. I assumed > that's what order-only prerequisites are for That's not what it's for. In fact, you can't achieve that in GNU Make (certainly not easily) or any other make I'm aware of. That's because such a feature would be quite difficult to implement without fundamentally changing the way make is typically designed. The documentation of order-only prequisites says what they're for: > A normal prerequisite makes two statements: first, it imposes an > order in which recipes will be invoked: the recipes for all > prerequisites of a target will be completed before the recipe for the > target is run. Second, it imposes a dependency relationship: if any > prerequisite is newer than the target, then the target is considered > out-of-date and must be rebuilt. > > [Order-only prerequisites] impose a specific ordering on the rules to > be invoked _without_ forcing the target to be updated if one of those > rules is executed. Makes treats order-only prereqs identically to "normal" prereqs in every way, EXCEPT that at the time where it checks to see whether the target needs to be rebuilt it doesn't consider the timestamps of the order-only prerequisites. That's all there is.
Re: Order-only prerequisites
On Wed, 07 Jun 2023 08:29:15 +0200 > As I said, a way to specify in which order recipes are invoked > (here, a before b) if they are invoked, without influencing whether > they are invoked (only a, only b or a and b, as given on the command > line). So you really don't want any target to depend upon another target? Then why do you care about the order? If order is important, what would happen if make is run with -j and starts several jobs in parallell? In practice, targets are built in the order that they are given on the command line or as dependencies in a rule. However, there is no guarantee that any Make is implemented that way. If you really have a need to specify the order of things you probably have that need because of some dependency between targets. regards Henrik
Re: Order-only prerequisites
Henrik Carlqvist wrote: > > Consider this makefile: > > > > .PHONY: a b > > a:; @echo a > > b:; @echo b > > b: | a > > Your problem with this Makefile is that it never creates any files a or b. That's why I made them phony. But that was just for demonstration. I get the same effects with this makefile (when a and b don't exist before): a:; touch a b:; touch b b: | a except for "'a' is up to date." instead of "Nothing to be done for 'a'.". > > If so, is there another way to achieve what I want? > > This totally depends upon what you want. As I said, a way to specify in which order recipes are invoked (here, a before b) if they are invoked, without influencing whether they are invoked (only a, only b or a and b, as given on the command line).
Re: Order-only prerequisites
> Consider this makefile: > > .PHONY: a b > a:; @echo a > b:; @echo b > b: | a Your problem with this Makefile is that it never creates any files a or b. This means that your order only prerequisite on a allways has to be made. > % make b a > a > b > make: Nothing to be done for 'a'. > > Correct order, but the last message seems strange. First as a (order-only) prerequisite for b, a is made. Then b is made. Then make was asked to make a but it does remember that a already has been made and prints out that nothing to be done. If your Makefile would have created the file a the order-only prerequisite would have made sense. It would then mean that b would depend upon the existance of a but it would not care about the timestamp of a. So if a exist and is newer than b there is no need to remake b of a is a order-only prerequisite. > If so, is there another way to achieve what I want? This totally depends upon what you want. regards Henrik
Re: order-only prerequisites don't behave as I'd have expected after reading the documentation
Hi Paul, thanks for the quick answer. On 06/12/2012 07:14 AM, Paul Smith wrote: On Mon, 2012-06-11 at 18:40 +0200, Stefano Lattarini wrote: The GNU make 3.82 manual reads: Normally, this is exactly what you want: if a target's prerequisite is updated, then the target should also be updated. Occasionally, however, you have a situation where you want to impose a specific ordering on the rules to be invoked without forcing the target to be updated if one of those rules is executed. But if I write a makefile like this: ALL = a b c d default: echo Specify a target: $(ALL); exit 1 .PHONY: $(ALL) $(ALL): @echo $@ a: | b b: | c c: | d then I get: $ make a # Not what I expected, but what actually happened. d c b a which is not what I'd have expected reading the documentation above; what I would have expected was that a alone would be run: $ make a # What I expected, but did not happen. a No, that's not how order-only prerequisites work. An order-only prerequisite is treated identically to a normal prerequisite except for exactly one thing: when make checks to see if a target needs to be remade, the time-last-modified values for any order-only prerequisites are not considered. Ah, all is clear now. Then I think we are dealing with a documentation bug here; in particular: - the name order-only prerequisites is IMHO poorly chosen, and don't really correspond to their actual semantics; a more appropriate might be weak prerequisites or existence-only prerequisites; - the explanation given in the manual is imprecise and confusing; since the explanation you've given here is OTOH very clear and concise, I suggest you report it in the manual; - it might make sense to state explicitly that order-only prereqs which are phony behaves in all ways like standard prerequisites. However, they are still considered prerequisites in that they are still built, themselves, if necessary, before the target. Since your targets are all phony (and none of them update their target file either) they will all always be remade every time. You can't see how order-only prerequisites work using this makefile. Thanks, Stefano ___ Bug-make mailing list Bug-make@gnu.org https://lists.gnu.org/mailman/listinfo/bug-make
Re: order-only prerequisites don't behave as I'd have expected after reading the documentation
On 06/12/2012 02:06 AM, Philip Guenther wrote:
On Mon, Jun 11, 2012 at 12:53 PM, Stefano Lattarini
stefano.lattar...@gmail.com wrote:
...
I was hoping to be able to the order-only prerequisites to enforce ordering
between .PHONY targets. At this point, I guess I should state the problem
I am trying to solve rather than just the attempts I've made at solving it.
Is there an easy, scalable way to specify in a GNUmakefile that, whenever
two given targets T1 and T2 (either phony or not) are to be updated, T1's
recipe must be executed before T2's, all without declaring any dependency
of T2 on T1? So that for example, assuming T1 and T2 are both phony:
$ make T1 # Only run T1's recipe
$ make T1 # Only run T2's recipe
(I think you meant make T2 there...)
Yes, sorry.
$ make T2 T1 # Run T1's recipe, then T2's recipe
$ make -j8 T2 T1 # Again, run T1's recipe, then T2's recipe
I think I would use a test on $(MAKECMDGOALS) to make T1 a
prerequisite of T2 if and only if T1 is a goal, say...
ifneq ($(filter T1,${MAKECMDGOALS}),)
T2: T1
endif
Not good enough; the order dependency I want between T1 and T2 should
have to work also when they are updated as dependencies of other targets:
$ cat Makefile
all: T1 T2
...
$ make all # Ought to work executing T1 before T2.
Regards,
Stefano
___
Bug-make mailing list
Bug-make@gnu.org
https://lists.gnu.org/mailman/listinfo/bug-make
Re: order-only prerequisites don't behave as I'd have expected after reading the documentation
On Tue, Jun 12, 2012 at 12:59 AM, Stefano Lattarini
stefano.lattar...@gmail.com wrote:
On 06/12/2012 02:06 AM, Philip Guenther wrote:
On Mon, Jun 11, 2012 at 12:53 PM, Stefano Lattarini
stefano.lattar...@gmail.com wrote:
...
I was hoping to be able to the order-only prerequisites to enforce ordering
between .PHONY targets. At this point, I guess I should state the problem
I am trying to solve rather than just the attempts I've made at solving it.
Is there an easy, scalable way to specify in a GNUmakefile that, whenever
two given targets T1 and T2 (either phony or not) are to be updated, T1's
recipe must be executed before T2's, all without declaring any dependency
of T2 on T1? So that for example, assuming T1 and T2 are both phony:
$ make T1 # Only run T1's recipe
$ make T2 # Only run T2's recipe
$ make T2 T1 # Run T1's recipe, then T2's recipe
$ make -j8 T2 T1 # Again, run T1's recipe, then T2's recipe
I think I would use a test on $(MAKECMDGOALS) to make T1 a
prerequisite of T2 if and only if T1 is a goal, say...
ifneq ($(filter T1,${MAKECMDGOALS}),)
T2: T1
endif
Not good enough; the order dependency I want between T1 and T2 should
have to work also when they are updated as dependencies of other targets:
$ cat Makefile
all: T1 T2
...
$ make all # Ought to work executing T1 before T2.
Given the design of make, with its lazy DAG building, what you are
asking for cannot be done automatically by make, as when it hits T2 as
a prerequisite it cannot know whether a not-yet-considered target will
end up having T1 as a prerequisite.
My gut reaction is that something in this setup is over-simplifying
things or misleading make. If T1 needs to be done before T2 _ever_,
then why not _always_ have it as a prerequisite of T2? Is the
.PHONYness of T1 a hack to get around some other limitation and using
some sort of timestamp file would let T1 be not-.PHONY and always be a
dependency of T2?
Whatever. Insufficient data. Workaround: use the MAKECMDGOALS test
previously cited but list all the targets that depend on T1 as well in
the $(filter) clause.
Philip Guenther
___
Bug-make mailing list
Bug-make@gnu.org
https://lists.gnu.org/mailman/listinfo/bug-make
Re: order-only prerequisites don't behave as I'd have expected after reading the documentation
On Mon, Jun 11, 2012 at 9:40 AM, Stefano Lattarini stefano.lattar...@gmail.com wrote: The GNU make 3.82 manual reads: Normally, this is exactly what you want: if a target's prerequisite is updated, then the target should also be updated. Occasionally, however, you have a situation where you want to impose a specific ordering on the rules to be invoked without forcing the target to be updated if one of those rules is executed. But if I write a makefile like this: ALL = a b c d default: echo Specify a target: $(ALL); exit 1 .PHONY: $(ALL) What is your intent for declaring all the targets PHONY in this Makefile? (Note: to quote 4.6 Phony Targets: A phony target should not be a prerequisite of a real target file; if it is, its recipe will be run every time `make' goes to update that file. As long as a phony target is never a prerequisite of a real target, the phony target recipe will be executed only when the phony target is a specified goal (*note Arguments to Specify the Goals: Goals.). ) Philip Guenther ___ Bug-make mailing list Bug-make@gnu.org https://lists.gnu.org/mailman/listinfo/bug-make
Re: order-only prerequisites don't behave as I'd have expected after reading the documentation
On 06/11/2012 07:03 PM, Philip Guenther wrote: On Mon, Jun 11, 2012 at 9:40 AM, Stefano Lattarini stefano.lattar...@gmail.com wrote: The GNU make 3.82 manual reads: Normally, this is exactly what you want: if a target's prerequisite is updated, then the target should also be updated. Occasionally, however, you have a situation where you want to impose a specific ordering on the rules to be invoked without forcing the target to be updated if one of those rules is executed. But if I write a makefile like this: ALL = a b c d default: echo Specify a target: $(ALL); exit 1 .PHONY: $(ALL) What is your intent for declaring all the targets PHONY in this Makefile? I was hoping to be able to the order-only prerequisites to enforce ordering between .PHONY targets. At this point, I guess I should state the problem I am trying to solve rather than just the attempts I've made at solving it. Is there an easy, scalable way to specify in a GNUmakefile that, whenever two given targets T1 and T2 (either phony or not) are to be updated, T1's recipe must be executed before T2's, all without declaring any dependency of T2 on T1? So that for example, assuming T1 and T2 are both phony: $ make T1 # Only run T1's recipe $ make T1 # Only run T2's recipe $ make T2 T1 # Run T1's recipe, then T2's recipe $ make -j8 T2 T1 # Again, run T1's recipe, then T2's recipe (Note: to quote 4.6 Phony Targets: A phony target should not be a prerequisite of a real target file; if it is, its recipe will be run every time `make' goes to update that file. As long as a phony target is never a prerequisite of a real target, the phony target recipe will be executed only when the phony target is a specified goal (*note Arguments to Specify the Goals: Goals.). ) Philip Guenther Regards, Stefano ___ Bug-make mailing list Bug-make@gnu.org https://lists.gnu.org/mailman/listinfo/bug-make
Re: order-only prerequisites don't behave as I'd have expected after reading the documentation
On Mon, Jun 11, 2012 at 12:53 PM, Stefano Lattarini
stefano.lattar...@gmail.com wrote:
...
I was hoping to be able to the order-only prerequisites to enforce ordering
between .PHONY targets. At this point, I guess I should state the problem
I am trying to solve rather than just the attempts I've made at solving it.
Is there an easy, scalable way to specify in a GNUmakefile that, whenever
two given targets T1 and T2 (either phony or not) are to be updated, T1's
recipe must be executed before T2's, all without declaring any dependency
of T2 on T1? So that for example, assuming T1 and T2 are both phony:
$ make T1 # Only run T1's recipe
$ make T1 # Only run T2's recipe
(I think you meant make T2 there...)
$ make T2 T1 # Run T1's recipe, then T2's recipe
$ make -j8 T2 T1 # Again, run T1's recipe, then T2's recipe
I think I would use a test on $(MAKECMDGOALS) to make T1 a
prerequisite of T2 if and only if T1 is a goal, say...
ifneq ($(filter T1,${MAKECMDGOALS}),)
T2: T1
endif
Philip Guenther
___
Bug-make mailing list
Bug-make@gnu.org
https://lists.gnu.org/mailman/listinfo/bug-make
Re: order-only prerequisites don't behave as I'd have expected after reading the documentation
On Mon, 2012-06-11 at 18:40 +0200, Stefano Lattarini wrote: The GNU make 3.82 manual reads: Normally, this is exactly what you want: if a target's prerequisite is updated, then the target should also be updated. Occasionally, however, you have a situation where you want to impose a specific ordering on the rules to be invoked without forcing the target to be updated if one of those rules is executed. But if I write a makefile like this: ALL = a b c d default: echo Specify a target: $(ALL); exit 1 .PHONY: $(ALL) $(ALL): @echo $@ a: | b b: | c c: | d then I get: $ make a # Not what I expected, but what actually happened. d c b a which is not what I'd have expected reading the documentation above; what I would have expected was that a alone would be run: $ make a # What I expected, but did not happen. a No, that's not how order-only prerequisites work. An order-only prerequisite is treated identically to a normal prerequisite except for exactly one thing: when make checks to see if a target needs to be remade, the time-last-modified values for any order-only prerequisites are not considered. However, they are still considered prerequisites in that they are still built, themselves, if necessary, before the target. Since your targets are all phony (and none of them update their target file either) they will all always be remade every time. You can't see how order-only prerequisites work using this makefile. ___ Bug-make mailing list Bug-make@gnu.org https://lists.gnu.org/mailman/listinfo/bug-make
