anchor.diff:  [source,makefile]
   ----
   define SPORE/util
  -  source: $(if $($1.use_fpu), fpu.c) common.c
  -  lang.c.defines: $(if $($1.use_fpu), USE_FPU)
  +  source: $(if $($1.option.use_fpu), fpu.c) common.c
  +  lang.c.defines: $(if $($1.option.use_fpu), USE_FPU)
   endef
   ----
   
  
positive.code:   # mylib is always linked because it is required by main
    libraries: mylib
    # No dependency if we are using a prebuilt library already in the path
    depends: $(if $($1.use_mylib_source), mylib)
  endef
  ----
  
  
negative.code: === Definition
  
  Spores are defined using a Moss structure with the `SPORE/` prefix.
  The structure instance name is present as argument `$1`.
  
  === Specialization
  
  