Date: Fri, 27 Jan 2012 16:05:37 +0000 From: Matthew Seaman <m.seaman@infracaninophile.co.uk> To: freebsd-ports <freebsd-ports@FreeBSD.org> Subject: BSD make -- Malformed conditional Message-ID: <4F22CB51.6070507@infracaninophile.co.uk>
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Dear all,
Posting this mostly for the archives, but it's probably relevant to some
people here too.
When hacking on Makefiles, should you wish to match an item in a list,
you might write something like this:
=2Efor item in ${LIST}
=2Eif ${item} =3D=3D ${THING} # Ooops!
THING_FOUND=3D 1
=2Eendif
=2Eendfor
This however is a snare and a delusion, and will lead to much weeping
and wailing, and error messages like so:
% make
"Makefile", line 7: Malformed conditional (foo =3D=3D ${THING})
"Makefile", line 9: if-less endif
"Makefile", line 7: Malformed conditional (bar =3D=3D ${THING})
"Makefile", line 9: if-less endif
"Makefile", line 7: Malformed conditional (baz =3D=3D ${THING})
"Makefile", line 9: if-less endif
"Makefile", line 7: Malformed conditional (blurfl =3D=3D ${THING})
"Makefile", line 9: if-less endif
make: fatal errors encountered -- cannot continue
Instead you should write your loops like this:
=2Efor item in ${LIST}
=2Eif ${THING} =3D=3D ${item}
THING_FOUND=3D 1
=2Eendif
=2Eendfor
As the make(1) manual page says on the subject of string comparisons
using =3D=3D or !=3D :
An expression may also be a numeric or string comparison: in this ca=
se,
the left-hand side must be a variable expansion, whereas the right-h=
and
side can be a constant or a variable expansion.
So it seems that despite appearing and behaving almost exactly like one,
the iterator in a .for loop is not actually a variable as such. It also
means that to match a constant string, you can't just write:
=2Efor item in ${LIST}
=2Eif ${item} =3D=3D "this" # Ooops
THIS_FOUND=3D1
=2Eendif
=2Eendfor
but have to assign the text "this" to a variable somewhere, and use the
second form.
Yes, you can use ${LIST:Mthis} instead, but using this construct can be
a bit tricky in itself...
% cat Makefile
LIST=3D foo bar baz blurfl
THING=3D baz
all:
@echo "OK \$${LIST:Mfoo} =3D ${LIST:Mfoo}"
@echo "Not OK \$${LIST:M\$${THING}} =3D ${LIST:M${THING}}"
% make
OK ${LIST:Mfoo} =3D foo
Not OK ${LIST:M${THING}} =3D }
Cheers,
Matthew
--=20
Dr Matthew J Seaman MA, D.Phil. 7 Priory Courtyard
Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate
JID: matthew@infracaninophile.co.uk Kent, CT11 9PW
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