RE: Copying files and making directories

[BShah]

See inline comments.

In principle, what you ask isn't impossible though I believe a bit of
lateral thinking will apply. The missing bit of information is "why?" - a
bit more of a description of what you are trying to achieve would be useful.
It would help to know which version of gmake you are currently using. I've
supplied what snipnets I can to solve particular issues but they are
probably version 3.79.1 dependant.

<SNIP>
> 
> 
> I'm working on a project that includes a lot of making directories and
> copying files.
> 
> I have the following problems:
> My makefiles are quite large and unwieldy.
> A make run will typically spend time copying already up-to-date files.
> A make run will typically log lots of failed (but ignored) 
> calls to 'mkdir' 
> 
> Writing explicit rules to avoid the last 2 problems would 
> make the makefiles
> even bigger.
> 
> I think I would like to be able to express the following rules.
> 
> 1) To build anything that is a directory, mkdir it.

How do you know what is a directory? If you have a list of directories or
can construct a list, this works quite well:

.PHONY: $(LIST_OF_DIRS)

# the command sequence says - if a directory exists, then do nothing
# else make it. The rule gets execed for each directory.
$(LIST_OF_DIRS):
        $(if $(wildcard $@),,mkdir $@)

all: $(LIST_OF_DIRS)
        @echo ++ Done creating.

> 2) Anything that is a directory is dependant on its parent directory

Not sure what the purpose of this is.

> 3) This is a generalisation of (2): Anything that has a path 
> in its name
> depends on that path, i.e. A/B/foo.c is dependant on A/B/

$(FILE_WITH_PATH): $(dir $(FILE_WITH_PATH))
        ...

> 4) If A is dependant on B and they have the same filenames 
> but different
> paths then A is build by copying B to A

I found it quite tricky to do this as a general case rule. I'm not entirely
sure that its possible in a straight-forward manner. I had a lot of
difficulties with cyclic dependencies with this. More thinking required,
once more information available.

Hope this helps a bit.
B.