Make: Can we Optimize make file targets? - makefile

Question

We are supporting 32 bit and 64 bit build in our workflow.For that We have multiple rules in makefiles which are separate for 32-bit and 64-bit. Let me show pair of rules which are same except for the string “32” vs “64” .
Makefile Snippet:-
$(TGTDIR32)/logdir/set_user.c: $(CURDIR)/slv/set_user.c
$(file_transfer)
$(TGTDIR64)/logdir/set_user.c: $(CURDIR)/slv/set_user.c
$(file_transfer)
If you notice, We have targets with same except for the string “32” vs “64”, i want to replace them by single rule/definition. Because we have hundreds of rules like above in our infrastructure code.
Do we have any simplified way in GNUmake to do that?
Thanks in Advance!

Answer 1

Targets which have the same prerequisites and recipe can simply be combined, like so:
$(TGTDIR32)/logdir/set_user.c $(TGTDIR64)/logdir/set_user.c: $(CURDIR)/slv/set_user.c
$(file_transfer)
or more generally:
THESE_TARGETS := $(TGTDIR32)/logdir/set_user.c $(TGTDIR64)/logdir/set_user.c # More...?
...
$(THESE_TARGETS): $(CURDIR)/slv/set_user.c
$(file_transfer)
If Make decides that any member of $(THESE_TARGETS) is out-of-date with respect to the prerequisites, then it will run the recipe for that target.
This makefile:
.PHONY: all clean
all: a b c
a: d e
touch $#
b: d e
touch $#
c: d e
touch $#
d:
touch $#
e:
touch $#
clean:
$(RM) a b c d e
is equivalent to this one:
.PHONY: all clean
all: a b c
a b c: d e
touch $#
d e:
touch $#
clean:
$(RM) a b c d e
Later
There are some static pattern rules...
The same applies. This makefile with static pattern rules:
.PHONY: default clean
default: a.k b.k
a.k: %.k: %.j
cp -f $< $#
b.k: %.k: %.j
cp -f $< $#
a.j:
touch $#
b.j:
touch $#
clean:
$(RM) a.k b.k a.j b.j
is equivalent to this one:
.PHONY: default clean
JS := a.j b.j
KS := $(JS:.j=.k)
default: $(KS)
$(KS): %.k: %.j
cp -f $< $#
$(JS):
touch $#
clean:
$(RM) $(JS) $(KS)

Answer 2

In my opinion this is an appropriate place to use recursive make, at least for the top-level build.
In this situation you could do something like this:
TGTDIR64 = ...
TGTDIR32 = ...
.PHONY: all all32 all64 build
all: all32 all64
all32:
$(MAKE) TGTDIR=$(TGTDIR32) build
all64:
$(MAKE) TGTDIR=$(TGTDIR64) build
# Things below here should just use TGTDIR
build: $(TGTDIR)/b1 $(TGTDIR)/b2
$(TGTDIR)/logdir/set_user.c: $(CURDIR)/slv/set_user.c
$(file_transfer)
$(HEADERGEN_NOTSPLIT_H_COPY): $(TGTDIR)/%.h: %.h $(copy_file)
...

Answer 3

The two rules are semantically identical, they only use a different way to refer to a "parameterized" target. Why you don't just use one target for this
$(TGTDIR)/logdir/set_user.c: $(CURDIR)/slv/set_user.c
$(file_transfer)
and use a properly configured TGTDIR (I suspect this would be something like "xxxx_32" vs "xxxx_64")?
You could achieve this in several ways; one typical would be
ifdef choose32
TGTDIR=xxxx_32
else
TGTDIR=xxxx_64
endif