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Date: Sat, 12 Feb 2005 18:45:24 -0800
From: Kris Kennaway <kris@obsecurity.org>
To: Kris Kennaway <kris@obsecurity.org>
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cc: hackers@FreeBSD.org
Subject: Re: Makefile .for and .if expansion
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On Sat, Feb 12, 2005 at 06:32:01PM -0800, Kris Kennaway wrote:
> The following small makefile doesn't behave as one would naively
> expect:
>=20
> MANLANG?=3Dfoo ""
> all:
> .for i in ${MANLANG}
> .if empty(${i})
>         @echo foo ${i}
> .endif
> .endfor
>=20
> ports-i386%make
> foo foo
> foo
>=20
> I think this is because the .if evaluation is happening too early, and
> it's not being done after the .for loop is expanded and the i variable
> is set.

Actually it looks like it's happening too late:

For: Iterator i List foo ""
For: end for 1
Global:i =3D ""
--- i =3D ""
=2Eif empty(i)
        @echo foo ""
=2Eendif

---- at line 3
Global:delete i
Global:i =3D foo
--- i =3D foo
=2Eif empty(i)
        @echo foo foo
=2Eendif

---- at line 3
Global:delete i

i.e. the series of .if statements are expanded out by .for and then
the variable i is deleted, so by the time the .if is evaluated the
unset variable evaluates to empty.

Kris

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