Better way to do conditional inclusion in make

[NGie Cooper]

On Thu, Feb 5, 2015 at 1:32 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.

Depending on implicit ordering like that is brittle and I'd rather not
enable this kind of pattern...