On Mon, Sep 13, 2021 at 11:16 PM Kaz Kylheku (gmake)
<729-670-0...@kylheku.com> wrote:
>
> On 2021-09-13 06:16, Masahiro Yamada wrote:
> > On Mon, Sep 13, 2021 at 9:23 PM Kaz Kylheku (gmake)
> > <729-670-0...@kylheku.com> wrote:
> >>
> >> On 2021-09-13 00:28, Masahiro Yamada wrote:
> >> > masahiro@oscar:~/workspace/foo$ export FOO=2
> >> > masahiro@oscar:~/workspace/foo$ make
> >> > Makefile:1: the origin of FOO is: environment
> >> > Makefile:2: the value of FOO is: 2
> >> > make -e -f Makefile.sub1 FOO=1
> >>
> >> Note that this FOO=1 will be exported to the environment. See the
> >> GNU Make 4.3 manual, section 5.7.2 Communicating Variables to a
> >> Sub-make:
> >>
> >> "Except by explicit request, make exports a variable only if it is
> >> either defined in the environment initially or set on the command
> >> line, and if its name consists only of letters, numbers, and
> >> underscores."
> >
> >
> > This is not answering my question.
>
> OK.
>
> > Without -e, all the sub-makes remember that
> > FOO's origin is 'command line'.
>
> OK, that is the real issue.
>
> Now, of course, the sub-make is not literally getting
> FOO=1 on the command line. Command-line variables are passed
> to sub-makes via the MAKEFLAGS environment variable.
>
> The -e option makes a difference here.
>
> $ cat Makefile
> $(info FOO (from $(origin FOO)) is $(FOO))
>
> .PHONY: all
>
> all:
> env | grep '^MAKE'
>
>
> First, baseline: no arguments, no environment. This is make 4.1:
>
>
> $ make
> FOO (from undefined) is
> env | grep '^MAKE'
> MAKEFLAGS=
> MAKE_TERMERR=/dev/pts/1
> MAKELEVEL=1
> MAKE_TERMOUT=/dev/pts/1
>
> $ make -e
> FOO (from undefined) is
> env | grep '^MAKE'
> MAKEFLAGS=e
> MAKE_TERMERR=/dev/pts/1
> MAKELEVEL=1
> MAKE_TERMOUT=/dev/pts/1
>
> Now, with a variable assignment:
>
> $ make FOO=1
> FOO (from command line) is 1
> env | grep '^MAKE'
> MAKEFLAGS= -- FOO=1
> MAKE_TERMERR=/dev/pts/1
> MAKELEVEL=1
> MAKEOVERRIDES=${-*-command-variables-*-}
> MAKE_TERMOUT=/dev/pts/1
>
> $ make -e FOO=1
> FOO (from command line) is 1
> env | grep '^MAKE'
> MAKEFLAGS=e -- $(MAKEOVERRIDES)
> MAKE_TERMERR=/dev/pts/1
> MAKELEVEL=1
> MAKEOVERRIDES=${-*-command-variables-*-}
> MAKE_TERMOUT=/dev/pts/1
>
> Without -e, MAKEFLAGS carries the command line variables
> itself.
>
> Without -e, MAKEFLAGS contains a reference to ${MAKEOVERRIDES},
> which contains a reference to ${-*-command-variables-*-}.
With -e, MAKEFLAGS contains...
^^^^
> But this -*-command-variables-*- is purely internal; it is
> not in the environment. It looks like it will refer to the
> literal command line. And so that could be why in the
> grandchild make, you are not seeing the origin of FOO as
> command line; it doesn't appear in ${-*-command-variables-*-}.
I do not have much knowledge of GNU make internal,
but your insight sounds right.
We have not got any feedback from Paul, but
this seems like a bug.
Even if it is a low-priority, let me raise this
in the bug tracking system.
> It seems odd because -e is supposed to be about the precedence
> between variables defined in the Makefile, versus environment.
> Yet this shows it is interacting with command line variable
> semantics.
>
> In the manual, -e/--environment-overrides is not specified
> in great detail. The Options Summary just says:
>
> Give variables taken from the environment precedence over
> variables from makefiles.
>
> and then refers to:
>
> See Variables from the Environment.
>
> That section only mentions -e in a parenthetical statement,
> and warns that using it is not recommended practice:
>
> (If the ‘-e’ flag is specified, then values from the environment
> override assignments in the makefile. See Summary of Options.
> But this is not recommended practice.)
>
> I.e. it says nothing more or less than the Summary of Options,
> except for adding that -e isn't recommended.
>
> It looks like -e is some sort of experimental hack with mysterious
> effects that is under-documented on purpose, with a warning not to
> use it.
>
>
--
Best Regards
Masahiro Yamada
