Re: how to conditionally pass a function to a function

[Paul Smith]

On Wed, 2008-10-29 at 11:26 -0400, Michael Ploujnikov wrote:
> define rule-generator
> $(1):
>         @echo "$(1) generating $(2)" && \                                     
>                  
>         $(call $(3)) && \                                                     
>                  
>         $(call $(4))
> endef
> 
> $(eval $(call 
> rule-generator,my-rule1,package-name,default-start-fun,default-end-fun))

You really don't want to use ifdef for this.  Ifdef is a preprocessor
statement and it can't be used inside of backslash-extended lines like
this.  It gets appended to the previous line and bad things happen.

Why don't you just use $(if ..)... or actually even $(or ...) would be
more efficient (one less variable expansion)?  Something like:

        define rule-generator
        $(1):
                @echo "$(1) generating $(2)" && \                               
                       
                $(call $(or $(3),$(default-start-fun))) && \                    
                                                  
                $(call $(or $(4),$(default-end-fun)))
        endef

(totally untested).