Re: [9fans] `mk` (from Plan9 ports) efficiency related issue

[Andy Spencer <andy753421@gmail.com>]

On 2011-01-17 19:31, Ciprian Dorin Craciun wrote:
>     * not all files of the same type are built by using the same rule;
> (for example for some files I want to enable debugging, for others
> not); thus I don't see how a meta-rule would solve this problem;
> (unless I create separate `mk` files or I resort to filename tags --
> for example I would call `*.debug.c` all C files that I want to be

Use a variable:

a_cflags=-g -Da
b_cflags=-g -Db
test: test.o a.o b.o
	gcc -o $target $prereq
%.o: %.c
	gcc $($stem^_cflags) -c -o $target $stem.c

Or only filename-tag the object files:

test: test.o a-debug.o b-opt.o c-prof.o
%.o: %.c
	gcc -c -o $target $prereq
%-opt.o: %.c
	gcc -O -c -o $target $prereq
%-debug.o: %.c
	gcc -g -c -o $target $prereq
%-prof.o: %.c
	gcc -p -c -o $target $prereq


>     * second, each file has a unique dependency graph -- for example
> one `*.c` file might include other headers than another `*.c` file in
> the same project; thus when updating a single header I want to be able
> to build only those `*.c` files that actually depend on it; (this
> observation is less important for C applications, but for other type
> of programs -- like Java -- this fine grained dependency tracking
> means a lot of saved computing power);

Have you looked at cpp -M? Many cpps will generate make style
dependencies for you, I think they'll work with mk as well. You can
include them and the use meta rules for all the real work.

It's still a large list of dependencies though, so it might not help you
in this case. I'm no sure if erlang has somethings similar or not.


>     * third, in my brief experience with make files, meta-rules are
> quite hard to get right... furthermore it is impossible to have two
> patterns like: `%.%.x`; just imagine I have two types of images:
> background and foreground and I want to superimpose them, then I would
> like to be able to write `%{foreground}.%{background}.jpg :
> %{foreground}.jpg %{background}.jpg ..."; (I know that I can resort
> here to "<| generating command" but it seems just plain wrong...)

Mk's meta rules are much easier to get right because they don't get
messed up by all of GNU Make's automatically added meta rules. Also:

default:V: circle-square.png

(.*)-(.*).png:R: \1.png \2.png
	composite $prereq $target

P.S. anyone know a better way to composite images using the
plan9/plan9port image tools?