Question

I recently found this piece of example code from the GNU make documentation that refers to the eval function. I really like it, but when I tried to test it on my machine (make 3.81/Debian), all it does is trying to link the server without compiling the c files first … why? Is make 3.81 not compatible?

Shell output:

$ make
cc     -o server
cc: no input files

Code:

 PROGRAMS    = server client

 server_OBJS = server.o server_priv.o server_access.o
 server_LIBS = priv protocol

 client_OBJS = client.o client_api.o client_mem.o
 client_LIBS = protocol

 # Everything after this is generic

 .PHONY: all
 all: $(PROGRAMS)

 define PROGRAM_template =
  $(1): $$($(1)_OBJS) $$($(1)_LIBS:%=-l%)
  ALL_OBJS   += $$($(1)_OBJS)
 endef

 $(foreach prog,$(PROGRAMS),$(eval $(call PROGRAM_template,$(prog))))

 $(PROGRAMS):
         $(LINK.o) $^ $(LDLIBS) -o $@

 clean:
         rm -f $(ALL_OBJS) $(PROGRAMS)

Answer 1

I think it will work if you remove the = from the define line:

define PROGRAM_template
  ...
endef

I’ve tested this with GNUMake 3.81. As for why this works and the version in the manual doesn’t, I have no idea.