Date: Wed, 4 Sep 2019 09:31:25 -0700 From: Enji Cooper <yaneurabeya@gmail.com> To: Ian Lepore <ian@freebsd.org> Cc: Kyle Evans <kevans@freebsd.org>, Poul-Henning Kamp <phk@phk.freebsd.dk>, current <current@freebsd.org> Subject: Re: Weird goings on with make::empty() Message-ID: <26F4833D-81C6-42B6-B6CD-DF62714FAAD8@gmail.com> In-Reply-To: <5ab957620b5e28f1d9de14df12f9fdf60d00fc35.camel@freebsd.org> References: <3843.1567598344@critter.freebsd.dk> <969A062A-A52A-49E3-B4E3-CC9377B08C80@gmail.com> <CACNAnaE7Gw=r92akmx=tXgGNb=H7GuKm7=iXX2cLtSAxNALikA@mail.gmail.com> <5ab957620b5e28f1d9de14df12f9fdf60d00fc35.camel@freebsd.org>
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> On Sep 4, 2019, at 07:58, Ian Lepore <ian@freebsd.org> wrote:
>=20
>> On Wed, 2019-09-04 at 09:33 -0500, Kyle Evans wrote:
>> On Wed, Sep 4, 2019 at 9:27 AM Enji Cooper <yaneurabeya@gmail.com>
>> wrote:
>>>=20
>>>=20
>>>> On Sep 4, 2019, at 04:59, Poul-Henning Kamp <phk@phk.freebsd.dk>
>>>> wrote:
>>>>=20
>>>> On:
>>>>=20
>>>> Repository Root: svn+ssh://repo.freebsd.org/base
>>>> Repository UUID: ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
>>>> Revision: 351809
>>>>=20
>>>> I built a kernel, but drm-current-kmod did not get compiled
>>>> from the new world order in /usr/local/sys/modules
>>>>=20
>>>> Debugging I ended up doing this to src/sys/conf/kern.post.mk:
>>>>=20
>>>> Index: sys/conf/kern.post.mk
>>>> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
>>>> =3D=3D=3D=3D=3D
>>>> --- sys/conf/kern.post.mk (revision 351809)
>>>> +++ sys/conf/kern.post.mk (working copy)
>>>> @@ -77,12 +77,14 @@
>>>> ${target:S/^reinstall$/install/:S/^clobber$/cleandir/}
>>>> .endif
>>>> .for module in ${LOCAL_MODULES}
>>>> -.if !empty(module)
>>>> + true "XXX A $(module) 2 ${LOCALBASE} 3 ${LOCAL_MODULES} 4
>>>> ${MODULES_WITH_WORLD}"
>>>> +#.if !empty(module)
>>>> + true "XXX B $(module) 2 ${LOCALBASE} 3 ${LOCAL_MODULES} 4
>>>> ${MODULES_WITH_WORLD}"
>>>> @${ECHODIR} "=3D=3D=3D> ${module}
>>>> (${target:S/^reinstall$/install/:S/^clobber$/cleandir/})"
>>>> @cd ${LOCAL_MODULES_DIR}/${module}; ${MKMODULESENV}
>>>> ${MAKE} \
>>>> DIRPRFX=3D"${module}/" \
>>>> ${target:S/^reinstall$/install/:S/^clobber$/cleandir/}
>>>> -.endif
>>>> +#.endif
>>>> .endfor
>>>> .endif
>>>> .endfor
>>>>=20
>>>> This gives me the expected output from buildkernel:
>>>>=20
>>>> true "XXX A drm-current-kmod 2 /usr/local 3 drm-current-kmod 4
>>>> "
>>>> true "XXX B drm-current-kmod 2 /usr/local 3 drm-current-kmod 4
>>>> "
>>>>=20
>>>> If I leave in the ".if !empty(module)" line in, I only get:
>>>>=20
>>>> true "XXX A drm-current-kmod 2 /usr/local 3 drm-current-kmod 4
>>>> "
>>>>=20
>>>> suggestions welcome...
>>>=20
>>> (CCing Kyle)
>>>=20
>>> This behavior change is probably caused by r351799.
>>>=20
>>> I personally think the code before Kyle=E2=80=99s change and after it wa=
s
>>> buggy. It=E2=80=99s not word splitting LOCAL_MODULES before iterating ov=
er
>>> it.
>>>=20
>>=20
>> I've backed out r351799 since it breaks usage of LOCAL_MODULES
>> (though
>> I really don't understand how empty works, apparently, and that makes
>> me sad)... please advise on a correct path forward, because it's not
>> clear to me.
>>=20
>> Thanks,
>>=20
>> Kyle Evans
>>=20
>=20
> I'm not positive, but I suspect this has to do with when variables are
> expanded. In particular, the loop variable for a .for is expanded on
> each loop iteration, but doesn't yet exist during parsing. I suspect
> that the .if is evaluated earlier, during parsing. For example, this
> makefile:
>=20
> all:
> .for x in a "" b
> .if empty(x)
> @echo empty
> .endif
> @echo ${x}
> .endfor
> @echo done
>=20
> gives this output:
>=20
> revolution > make -f /tmp/Makefile=20
> empty
> a
> empty
>=20
> empty
> b
> done
>=20
> The way I interpret that is that empty(x) is true during parsing, so
> the for loop is generated to contain "@echo empty" and "@echo ${x}",
> then the for loop actually runs and prints both "empty" and the value
> of ${x} on each iteration.
Correct. Word splitting is the key. I=E2=80=99ll take a stab at this later o=
n today.
Thanks,
-Enji=
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