Subject: Re: New possibility to move "obj" logic *out* of make(1)
To: None <tech-toolchain@netbsd.org>
From: Todd Vierling <tv@wasabisystems.com>
List: tech-toolchain
Date: 10/31/2001 09:18:01
On Wed, 31 Oct 2001, Todd Vierling wrote:

: Note that the one upshot of moving all objdir handling to <bsd.obj.mk> does
: have one noticeable impact:  pre-evaluating variables (using := or !=), or
: dependency rules, containing an explicit ${.OBJDIR} before including
: <bsd.obj.mk>, will probably evaluate to the wrong thing.  However, typically
: an explicit ${.OBJDIR} is not needed, and I am running a full-text grep on
: the source tree to find the locations where this can be fixed in our tree.

Let me clarify a confusion that has already been noted:

This effect only applies to explicit evaluation of ${.OBJDIR} by the parser
before <bsd.obj.mk> is included.  This only happes in three cases:

VARNAME:=	value
VARNAME!=	value
targetname: value

If "value" above contains ${.OBJDIR} (directly or indirectly), it is
evaluated during the Makefile parsing, rather than during building, and thus
will evaluate to the value of ${.OBJDIR} at the moment that Makefile line
is reached.  However, the standard cases:

VARNAME=	value
VARNAME+=	value
	(a command inside a make rule, containing value)

are not evaluated until all Makefiles and included Makefile fragments have
been read and parsed.  In most cases, the explicit references we have to
${.OBJDIR} are one of these latter three cases.

Now, since make actually chdir()s to the .OBJDIR, in most cases an explicit
reference to ${.OBJDIR} is unnecessary, and from what I've seen of the
currently-running grep so far, almost all cases can have the explicit
reference nuked.

-- 
-- Todd Vierling <tv@wasabisystems.com>  *  Wasabi & NetBSD:  Run with it.
-- CDs, Integration, Embedding, Support -- http://www.wasabisystems.com/