Better way to do conditional inclusion in make

[Warner Losh]

> On Feb 5, 2015, at 2:32 PM, Dimitry Andric <dim at freebsd.org> wrote:
> 
> On 05 Feb 2015, at 18:56, Warner Losh <imp at bsdimp.com> wrote:
>> 
>> We know that MK_foo is always going to be yes or no
>> for build options. We can leverage that fact, and the fact that bmake is so much better at variable
>> expansion than fmake was (especially in the early days) to instead move to something like:
>> 
>> FILES=list of unconditional files here ${FILES.yes}
>> FILES.${MK_foo}+=foo bar biz
>> FILES.${MK_baz}+=baz bing boo
>> 
>> which eliminates a whole lot of needless .if / .endif lines, lots of extra blank lines, etc.
>> 
>> Comments?
> 
> One disadvantage is that you then cannot intersperse MK_foo files or
> subdirs in between unconditional ones, and keep a certain order, e.g.
> like:
> 
> FILES+= a b c
> .if ${MK_foo} != "no"
> FILES+= d e f
> .endif
> FILES+= g h i
> 
> Of course, this is only important for a few particular places, most of
> the tree should not care too much about the order in which subdirs or
> files are built.

I can’t think of any places where this matters. The only place where it used to
matter was library ordering, but that’s been fixed. And if there is any other places
in the tree where this matters, that should be listed as a real dependency and not
rely on the order which isn’t -j safe.

Warner