[CMake] actually using cmake alternative to convenience libraries

[Bill Hoffman]

On 11/17/2015 10:37 AM, Jack Stalnaker wrote:
> I'm trying to figure out the best way to handle something that was a
> convenience lib under autotools. I realize that there's a FAQ entry here:
>
> https://cmake.org/Wiki/CMake_FAQ#Does_CMake_support_.22convenience.22_libraries.3F
>
> But its terse 2 paragraphs don't say how to actually do what it
> suggests. My problem is this. I have this source tree:
>
> lib
> |--foo.c
> |--foo.h
> |--bar.c
> |--bar.h
> |--baz.c
> src
> |--goo.c
>
> In lib, I need to somehow collectively refer to foo and bar. Okay, so I
> can create a variable:
>
> set(foobarSRCS foo.c bar.c)
> set(foobarLIBS ${externalLibFound})
>
> which is what the FAQ entry seems to suggest. However, this variable is
> not visible to goo.c. Okay, so as an alternative, I can do this:
>
> set(foobarSRCS foo.c bar.c PARENT_SCOPE), etc.
>
> but now the variable is not visible to baz.c, which also must include
> the srcs to create a module library called _baz! I can of course do
> something like this:
>
> set(foobarSRCSLOC foo.c bar.c)
> set(foobarSRCS ${foobarSRCSLOC} PARENT_SCOPE)
>
> but this feels dirty and repetitive.
>
> I also realize that I can just create the variables in src, but that
> kind of defeats the entire purpose of walling of the common libs and
> their dependencies in the first place.
>
> Is this the right way to work, or am I missing something simple?
There is a new feature to do that:

https://cmake.org/Wiki/CMake/Tutorials/Object_Library

-- 
Bill Hoffman
Kitware, Inc.
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