GNU Make: wildcarding files in a stem's directory in a static pattern rule

Question

Searched a bunch, hope I didn't miss something obvious...

I have multiple book directories. Each has a single *.ditamap file (always named for the book) that references several dozen accompanying *.dita topic files:

makefile

book1/
  book1.ditamap  intro.dita  topic1.dita  topic2.dita  glossary.dita

book2/
  book2.ditamap  about.dita  topicA.dita  topicB.dita  appendix.dita

book3/
  book3.ditamap  cmd1.dita  cmd2.dita cmd3.dita

The XHTML output (target) for a book depends on its single .ditamap file plus all the *.dita files in that book directory (prerequisites). The makefile is placed alongside the book directories.

Building XHTML for a book creates an output XHTML directory inside that book directory, with an index.html file that I use as the target:

book1/
  book1.ditamap  intro.dita  topic1.dita  topic2.dita  glossary.dita

  book1/book1_xhtml/
    index.html  ...more html and CSS files...

The following static pattern rule will rebuild the XHTML directory inside any book directory where the *.ditamap file has changed:

ditamap_files := $(wildcard */*.ditamap)
xhtml_files := $(patsubst %.ditamap,%_xhtml/index.html,${ditamap_files})

all: dita xhtml
dita: ${ditamap_files}
xhtml: ${xhtml_files}

${xhtml_files}: %_xhtml/index.html: %.ditamap
        dita -i "${<}" -f xhtml -o "${*}_xhtml"

(Side note: make nicely handles building the path to the index.html target thanks to its clever directory-handling rules!)

However, I haven't found a way to extend this rule to be sensitive to the *.dita files too. Whenever .ditamap or .dita has changed inside the book directory, the book XHTML file must be rebuilt.

I tried stuff like

${xhtml_files}: %_xhtml/index.html: %.ditamap $(wildcard $(dir %)/*.dita)
#                                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^
        dita -i "${<}" -f xhtml -o "${*}_xhtml" 2>&1 | tee "${*}_xhtml.out"

but this completely fails to work because wildcards aren't supported in static pattern rules. Somehow I need to collect wildcarded files within the directory of the stem of each target, then make them prerequisites for that book.

Renaud Pacalet Renaud Pacalet · Accepted Answer · 2018-11-06T15:53:25

Secondary expansion, maybe:

.SECONDEXPANSION:

$(xhtml_files): %_xhtml/index.html: %.ditamap $$(wildcard $$(dir $$*)/*.dita)
    dita -i "$<" -f xhtml -o "$*_xhtml"

By the way, did you consider that dita files can change but also appear or disappear? Is this possible? If it is, what do you want to do? And do you know already how to detect this?

GNU Make: wildcarding files in a stem's directory in a static pattern rule

1 Answers