GNU make with many target directories

Question

I have to integrate the generation of many HTML files in an existing Makefile. The problem is that the HTML files need to reside in many different directories. My i

Answer 1

Your active implicit rule makes $(rootdir)/build/doc/2009/06/01/some.html depend on $(rootdir)/build/doc/2009/06/01/some.st. If $(rootdir)/build/doc/2009/06/01/some.st doesn't exist then the rule won't be used/found.

The commented out rule makes $(rootdir)/build/doc/2009/06/01/some.html depend on some.st.

One solution is to make you're source layout match your destination/result layout.

Another option is to create the rules as required with eval. But that will be quite complicated:

define HTML_template
 $(1) : $(basename $(1))
      cp $< $@
endef

$(foreach htmlfile,$(html),$(eval $(call HTML_template,$(htmlfile))))

Answer 2

An other possibility is to have the commando make call itself recursively with the argument -C with every output directory. Recursive make is somewhat the standard way to deal with subdirectories, but beware of the implications mentioned in the article "Recursive Make Considered Harmful"

Answer 3

Like Maria Shalnova I like recursive make (though I disagree with "Recursive Make Considered Harmful"), and in general it's better to make something HERE from a source THERE, not the reverse. But if you must, I suggest a slight improvement: have generateHtml generate only the RULE, not the COMMANDS.

Answer 4

The best solution I found so far is to generate an implicit rule per target directory via foreach-eval-call, as explained in the GNU make manual. I have no idea how this scales to a few thousand target directories, but we will see...

If you have a better solution, please post it!

Here is the code:

rootdir  = /home/user/project/doc
HPC      = /usr/local/bin/hpc

html = $(rootdir)/build/doc/2009/06/01/some.html \
       $(rootdir)/build/doc/2009/06/02/some.html

targetdirs = $(rootdir)/build/doc/2009/06/01 \
             $(rootdir)/build/doc/2009/06/02

define generateHtml
 $(1)/%.html: %.st
    -mkdir -p $(1)
    $(HPC) -o $$@ $$<
endef   

$(foreach targetdir, $(targetdirs), $(eval $(call generateHtml, $(targetdir))))

.PHONY: all
all: $(html)