multi-wildcard pattern rules of GNU Make

Question

I want to write something like regex:

SRC:=\"a.dat.1 a.dat.2\"    
$(SRC): %.dat.%: (\\\\1).rlt.(\\\\2)    
      dat2rlt $^ $@

so that

Answer 1

I'm afraid what you are trying to do is not possible the way you suggest to do it, since - as you already mention - (GNU) make only allows a single stem '%', see http://www.gnu.org/software/make/manual/make.html#Pattern-Rules:

A pattern rule looks like an ordinary rule, except that its target contains the character ‘%’ (exactly one of them).

Without it, creating such 'multi-dimensional' targets is cumbersome.

One way around this is by rebuilding the name of the dependency in the command (rather than in the dependency list):

SRC := a.dat.1 a.dat.2

all : $(SRC:%=%.dat2rlt)

%.dat2rlt :
    dat2rtl $(word 1,$(subst ., ,$*)).rlt.$(word 2,$(subst ., ,$*)) $*

Of course, however, this way you would lose the dependency, it will not rebuild once the rlt has been updated.

The only way I can see to address that is by generating the rules explicitly:

SRC := a.dat.1 a.dat.2

all : $(SRC)

define GEN_RULE
$1.dat.$2 : $1.rlt.$2
    dat2rtl $$< $$@
endef

$(foreach src,$(SRC),$(eval $(call GEN_RULE,$(word 1,$(subst ., ,$(src))),$(word 3,$(subst ., ,$(src))))))