I Like Makefiles

Re:I Like Makefiles by chongli on Saturday September 21, 2024 @07:05AM (#41609179)

A single target (a single node in the dependency graph) of Make does exactly one thing: it takes input files, some dependencies and generates _exactly_one_ output file.

Yes, but this is not particularly relevant to the user. With pattern rules it's trivial to define a large number of targets automatically, such as in the example (from the manual):

    objects = foo.o bar.o

    all: $(objects)

    $(objects): %.o: %.c
            $(CC) -c $(CFLAGS) $< -o $@

[ Parent | on HN ]

Re:I Like Makefiles by ReleaseCandidat on Saturday September 21, 2024 @07:32AM (#41609305)

I have been unclear in my formulation, sorry.

The problem is a target with more than one output files, that target would look something like, which does work

    foo bar: baz
         compile $< -o foo -o bar

but as this is the same as writing

    foo: baz
         compile $< -o foo -o bar

    bar: baz
         compile $< -o foo -o bar

to generate `foo` and `bar` the rule is run twice in a parallel build (`make -j 2`. Which may just be unnecessary or it may break the whole build.

[ Parent | on HN ]

Re:I Like Makefiles by frumiousirc on Saturday September 21, 2024 @07:48AM (#41609375)

https://www.gnu.org/software/make/manual/html_node/Multiple-...

Scroll down to "Grouped targets". I think these address the concern you raise.

The snippet you have shown is an example of the "independent targets" pattern which the first half of that page also covers.

[ Parent | on HN ]

Re:I Like Makefiles by ReleaseCandidat on Saturday September 21, 2024 @10:15AM (#41610126)

Thanks, that's it. It has been introduced with GNU Make 4.3, January 2020 https://lists.gnu.org/archive/html/info-gnu/2020-01/msg00004...

[ Parent | on HN ]

Re:I Like Makefiles by robinsonb5 on Saturday September 21, 2024 @07:45AM (#41609359)

So can that be solved like this, or is there some other subtlety I'm missing?

  foo: baz
    compile $< -o foo -o bar

  bar: foo

(Can someone tell me how to do code tags on HN please? :) Edit: fixed now, thanks!)

[ Parent | on HN ]

Re:I Like Makefiles by oneeyedpigeon on Saturday September 21, 2024 @07:54AM (#41609398)

> Text after a blank line that is indented by two or more spaces is reproduced verbatim. (This is intended for code.)

(from https://news.ycombinator.com/formatdoc)

[ Parent | on HN ]

Re:I Like Makefiles by mauvehaus on Saturday September 21, 2024 @08:36AM (#41609580)

Among other things, now you have to maintain a set of dummy targets. If you have a variable (possibly generated) that is basically

  A_MESS_OF_FILES := foo bar zot

You now have to create dummy targets for bar, baz, and zot and not forget to add them. Or maybe break it into

  MAIN_FILE := foo
  SUBORDINATE_FILES := bar zot

  foo: baz
    sudo make me a foo

  $(SUBORDINATE_FILES): %: foo

[ Parent | on HN ]

Re:I Like Makefiles by ReleaseCandidat on Saturday September 21, 2024 @10:18AM (#41610151)

Subtlety. Now the dependencies are `baz` -> `foo` -> `bar`, that is `foo` is a temporary target and won't be (re)build if `bar` already exists. Which may or may not be a problem. This temporary target (whatever the actual term is) can be "elevated" to a "normal" target with the use of some special target (which I'm too lazy to look up right now).

[ Parent | on HN ]