Re: simple assignment of target-specific variables

[David Boyce]

I think you misunderstood the point of my message. The date doesn't matter here, it was just a random command in a demo makefile. In fact the command was originally "hostname" but I was concerned about leaking even the smallest amount of internal data about my workplace so I figured "date" was safest since the time is public info.

> There could be multiple places where it is needed.

When I say "needed" here I mean specifically that the recipe runs. Clearly a target-specific variable is 'needed' iff the target is built. It's not a question of how many places the variable is expanded, it's a boolean thing: the target is built or not built, the target-specific variable is needed or not.

David

On Tue, Jun 9, 2020 at 8:52 AM Dmitry Goncharov via Bug reports and discussion for GNU make <bug-make@gnu.org> wrote:

On Tue, Jun 9, 2020 at 9:10 AM David Boyce <dboyce@broadcom.com> wrote:
> TARGETS := aa bb cc dd
> $(TARGETS): at := $(shell set -x; date)

Despite the same name "at" those are different variables.
Given that there are 4 simple variables defined, 4 calls to date take place.

$ cat makefile
.PHONY: all
all: aa bb
aa: at := $(shell set -x; date)
$(shell sleep 5)
bb: at := $(shell set -x; date)
aa bb:
        @:$(info Making $@ at $(at))
$ make
+ date
+ date
Making aa at Tue Jun  9 11:50:08 EDT 2020
Making bb at Tue Jun  9 11:50:13 EDT 2020

Note, aa's at is 5 seconds earlier then bb's.


> But in a target-specific context should the variable be considered "defined" at the time it's parsed or at the time it's needed?
There could be multiple places where it is needed.

regards, Dmitry