Re: conditional macro definitions

[bill]

Eric West wrote:

> On Sunday 20 November 2005 02:50 am, bill wrote:
>  
>
> > The syntax
> > foo:=CFLAGS=-DFOO
> > for redefining CFLAGS for the target foo seems like a great thing,
> > but it's not valid in gnu-make.  I'm currently setting up my make
> > files so that I type "make DEBUG=1" and then defining CFLAGS
> > conditionally based on the definition of DEBUG.  I'd much rather type
> > "make debug" and use the syntax given above.  2 questions:
> >
> > 1)  Is it possible to do something like:
> > if target==debug;    CFLAGS = -DDEBUG; end if
> > rather than:
> > ifdef DEBUG; CFLAGS = -DDEBUG; end if
> >
> > 2) Why is the conditional macro definition syntax not incorporated
> > into gnu-make?
> > It seems like a good idea.
> >
> >    
>
>  

> You can tailor a make file to do (1). One approach is to test the 
> target(s) passed on the command line using the MAKECMDGOALS variable. 
> This variable is initialized by make when it is invoked. 
>
> Example:
>
> $ cat make.tst
> CFLAGS := -DXXXX
>
> ifneq (,$(findstring debug,${MAKECMDGOALS}))
>    CFLAGS += -DDEBUG
>    ifeq "$(words ${MAKECMDGOALS})" "1"
>        tgt := all
>    endif
> endif
>
> all: FRC
>        # all: CFLAGS = ${CFLAGS}
>
> foo: FRC
>        # foo: CFLAGS = ${CFLAGS}
>
> .PHONY : debug
> debug : ${tgt}
>         @echo > /dev/null
>
> FRC:
>
> $ make -f make.tst debug
> # all: CFLAGS = -DXXXX -DDEBUG
> $ make -f make.tst debug foo
> # foo: CFLAGS = -DXXXX -DDEBUG
> $ make -f make.tst foo
> # foo: CFLAGS = -DXXXX
> $
>
> Variations on this theme are left to your imagination.
>
>  --Eric West
>
>  
Thanks to everyone who responded to that question.   I'm a little 
confused about
how to deal with the issue that the conditional definition seems to 
occur too late.
In the following example, I modify the value of $(DIR) when the target 
is debug.
But the target $(DIR) maintains the old value.  So when I "make debug", 
there is no
rule to build /tmp/debug.  How do I make the conditional values be targets?

% rmdir /tmp/foo
% cat makefile

DIR = /tmp/foo

debug : DIR = /tmp/debug

all: $(DIR)

debug: all

$(DIR):
       mkdir -p $@
       @echo target:$@
       @echo DIR:$(DIR)
% make debug
mkdir -p /tmp/foo
target:/tmp/foo
DIR:/tmp/debug