Why Use Make - Hackdot

Re:Why Use Make by SomeCallMeTim on Monday February 25, 2013 @06:53PM (#5282751)

> messing up with = and :=

Sorry, but I wasn't messing up those two. That's Makefile 101 knowledge; I'm talking about crazy advanced stuff, where := doesn't work the way you expect.

Even := doesn't do what you want if, after the Makefile has been loaded and you've used := three times on the same variable, ALL the instances of that variable are replaced by the last assignment. Here's an example:

    FOO:=1

    rule1 :
        echo $(FOO)

    FOO:=2

    rule2 :
        echo $(FOO)

make rule1 and make rule2 both echo 2. $(FOO) is evaluated in both cases AFTER the Makefile is loaded.

[ Parent | on HN ]

Re:Why Use Make by sankl on Thursday February 28, 2013 @01:31AM (#5297408)

Target specific variables do this job:

    rule1 : FOO:=1
    rule1 :
        echo $(FOO)

    rule2 : FOO:=2
    rule2 :
        echo $(FOO)

[ Parent | on HN ]

Re:Why Use Make by SomeCallMeTim on Friday March 01, 2013 @01:50PM (#5306121)

Interesting. Didn't know this trick.

Turns out it wouldn't work for the usage pattern I needed (my example was simplified -- typically the variable settings would all happen in another file, and they couldn't happen on a target line because there wouldn't be a single target to use, in addition to just being ugly for that use), but it's good to know.

[ Parent | on HN ]