Re: Compacting link-rules

[Paul Smith]

On Thu, 2018-10-18 at 17:40 +0200, Gisle Vanem wrote:
>    bin/%.exe: $($(@F)_OBJ) $(LIBS)
>            $(call link_EXE, $@, $^)

This cannot work because automatic variables like $@, etc. are only
valid _inside a recipe_.  They are not set and cannot be used in target
or prerequisite lists: they expand to the empty string.

You have two choices.  You can either separate the prerequisites from
the recipe, like this:

  bin/%.exe:
          $(call link_EXE,$@,$^)

  bin/animation.exe: $(animation_OBJ) $(LIBS)
  bin/barchart.exe: $(barchart_OBJ) $(LIBS)

Or, you can enable secondary expansion which will allow you to write:

  .SECONDEXPANSION:

  bin/%.exe: $$($$(@F)_OBJ) $(LIBS)
            $(call link_EXE, $@, $^)

(note the extra "$" in the variable references.  See:

https://www.gnu.org/software/make/manual/make.html#Secondary-Expansion