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Date: Sat, 12 Feb 2005 18:32:01 -0800
From: Kris Kennaway <kris@obsecurity.org>
To: hackers@FreeBSD.org
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Subject: Makefile .for and .if expansion
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--IiVenqGWf+H9Y6IX
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The following small makefile doesn't behave as one would naively
expect:

MANLANG?=foo ""
all:
.for i in ${MANLANG}
.if empty(${i})
        @echo foo ${i}
.endif
.endfor

ports-i386%make
foo foo
foo

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.

In order to get this to work I seem to have to do the following:

MANLANG?=foo ""
.for i in ${MANLANG}
j=      ${i}
.if (${j} != "\"\"")
.for l in ${j}
k+=     ${l}
.endfor
.endif
.endfor
all:
        @echo ${k}

ports-i386%make
foo

If I remove the inner .for it breaks, and if I remove the j assignment
it breaks.  Also if I try and remove the use of k and put an echo
inside the inner .for (with the all: preceding the whole loop) it
breaks.

This is extremely nasty.

Am I missing an easier way to do this?

Kris
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