Re: Parallel make not working the way I expect...

[David Wuertele]

Thanks for the help!

Philip Guenther <guenther <at> gmail.com> writes:

> It might look like it tells make that to build $(LOTS_OF_FILES),
> invoke $(CWBLOF) just once, but that's not correct.  A (non-pattern)
> rule with multiple targets is *exactly* the same as if each target was
> listed separately, ala:
> 
> one: Makefile
>       $(COMMAND_WHICH_BUILDS_LOTS_OF_FILES)
> two: Makefile:
>       $(COMMAND_WHICH_BUILDS_LOTS_OF_FILES)
> ...etc

OK.

> Choice 2) use a pattern rule with multiple targets so that make knows
> that one command builds all of them.  You should arrange for the files
> to have names that follow some sort of pattern (all have the same
> prefix, of suffix, or *something* in common) so that the patterns you
> give use to match them make some sense.

There are hundereds of times when I have to build someone else's code by running
"$(MAKE) -C $(SOMEONE_ELSES_DIR)", and it spits out multiple files that I
require.  For example, the subdir might be "portmap_4" and it makes "portmap",
"pmap_dump", and "pmap_set".  I don't have any control over their makefile, so I
can't arrange for the files to have a common prefix.  Except:  maybe I could use
the subdirectory as a prefix?  I tried this:

LOTS_OF_FILES := dir/one dir/two dir/three dir/four dir/five dir/six

all: $(LOTS_OF_FILES)

COMMAND_WHICH_BUILDS_LOTS_OF_FILES := for file in $(LOTS_OF_FILES); do mkdir -p
`dirname $$file` && echo hello >> $$file; done

$(LOTS_OF_FILES): dir/%: Makefile
        $(COMMAND_WHICH_BUILDS_LOTS_OF_FILES)

clean:
        rm -rf $(LOTS_OF_FILES)

Is that what you mean by a pattern rule?  It had the same problem as before:

$ make -j 10
for file in dir/one dir/two dir/three dir/four dir/five dir/six; do mkdir -p
`dirname $file` && echo hello >> $file; done
for file in dir/one dir/two dir/three dir/four dir/five dir/six; do mkdir -p
`dirname $file` && echo hello >> $file; done
for file in dir/one dir/two dir/three dir/four dir/five dir/six; do mkdir -p
`dirname $file` && echo hello >> $file; done
for file in dir/one dir/two dir/three dir/four dir/five dir/six; do mkdir -p
`dirname $file` && echo hello >> $file; done
for file in dir/one dir/two dir/three dir/four dir/five dir/six; do mkdir -p
`dirname $file` && echo hello >> $file; done
for file in dir/one dir/two dir/three dir/four dir/five dir/six; do mkdir -p
`dirname $file` && echo hello >> $file; done
$ 

Dave