[clug] Playing funny with make..

[Daniel Pittman]

Andrew Janke <a.janke at gmail.com> writes:

>> Probably.  Do you need to keep the intermediate files?
>
> Definitely.
>
>>  Think about that,
>> because by default the chained rules don't, but you can instruct make to.
>
> you mean via:  .SECONDARY: ...

I don't honestly remember.  There is some mechanism, perhaps a command line
switch, or a setting in the Makefile, that tells make not to delete
intermediate stuff.  (...and I am too lazy to read the info page for you. ;)

>> Anyway, the better way is almost certainly to use the "chained rules" stuff
>> that can string together groups of transformations.
>
> This is what I _thought_ I was doing... :)

[...]

> Although in my case I would have to expand "whatever.doc" to 1000+
> files. Thus my question about at what point should I expect make to break
> down with such games?

I don't honestly know.  I only ever do very, very small batch processing
things in make.  FWIW, I would probably use a patsubst, or shell, callout to
do the 1000 item dependency list dynamically rather than statically. :)

>> ...then, once you have generic rules to produce your output from the input
>> you can use one single "source to target" transformation and let make
>> figure out the bits in the middle.
>
> Hrm, perhaps I am doing it wrong in other ways then.  Currently the rough
> overview of dependencies is this: (main.html is a summary output file, and
> this is simplified in which there are only three processing stages).
>
> all: main.html
>
> main.html: 01-aaa.chk 02-bbb.chk 03-ccc.chk ...
>    [dostuff]
>
>
> all.01-aaa: $(addsuffix .01-aaa.chk, $(files))
>    touch $@

%-aaa.chk: %

>
> all.02-bbb: $(addsuffix .01-aaa.chk, $(files))
>    touch $@
>
> all.03-ccc: $(addsuffix .02-bbb.chk, $(files))
>    touch $@
>
>
> %.01-aaa.chk: %.native.chk
>    [dostuff]
>
> %.02-bbb.chk: %.01-aaa.chk
>    [dostuff]
>
> %.03-ccc.chk: %.02-bbb.chk
>    [dostuff]
>
>
>
> And the chaining is not happening.  Is this then because main.html should
> instead only depend on the last stage?  ie:
>
> main.html: 03-ccc.chk ...
>    [dostuff]
>
> and I should ignore the all.02-bbb and 03-ccc rules?

Yes, that is the mechanism.  You specify *pattern* rules for each stage, using
the '%' wildcard to replace the individual filename, and let make string that
together.

So, the pattern rule '%.o: %.c' can stand in for *any* 'whatever.o:
whatever.c' rule.

So, for a three stage process (with my own names, because I am not certain of
the names of yours, I fear):

results: a.stage3 b.stage3 ... z.stage3
    # whatever you have to do here...

%.stage3: %.stage2
    make-stage3 > $< < $@  # or is that back to front?

%.stage2: stage1-processed-%.data
    make-stage2 ...

stage1-processed-%.data: %.raw
    # turn a.raw into stage1-processed-a.data

Then run 'make results' and you get:

  results => a.stage3  # supplied by you
    a.stage3 => a.stage2  # make infers this
      a.stage2 => stage1-processed-a.data
        stage1-processed-a.data => a.raw
    b.stage3 => b.stage2
      # ...etc

You have to tell make *somewhere* what results you want, but it can calculate
the intermediate path for you automatically.

FWIW, the system includes a whole bunch of rules of that sort, such as:

    %.o: %.c
        cc -c -o $@ $<

'make -p' will dump the internal database, including implicit variables and
implicit rules, to give you a solid example of what the defaults are.

Regards,
        Daniel

-- 
✣ Daniel Pittman            ✉ daniel at rimspace.net            ☎ +61 401 155 707
               ♽ made with 100 percent post-consumer electrons
   Looking for work?  Love Perl?  In Melbourne, Australia?  We are hiring.