[CMake] Build only what you need in third party libs

[Tim St. Clair]

Watch out gentoo, and buildroot, here comes cmake ;-)

I just tested and it works like a charm, nice job!

just as a side note for other users, make certain you don't "quote"
your commands.

Cheers,
Tim

On Tue, Dec 22, 2009 at 8:50 AM, David Cole <david.cole at kitware.com> wrote:
> On Tue, Dec 22, 2009 at 9:37 AM, Troy D. Straszheim <troy at resophonic.com>
> wrote:
>>
>> David Cole <david.cole at kitware.com> writes:
>>
>> > On Tue, Dec 22, 2009 at 7:58 AM, David Wolfe <dwolfe at fifthsally.com>
>> > wrote:
>> >
>> >     On 12/22/2009 7:11 AM, David Wolfe wrote:
>> >
>> >                                                    Most of our external
>> >         dependencies aren't even built using CMake, so 'CMake-ifying'
>> >         everything
>> >         under one big über-build hardly seems worth it...
>> >
>> >
>> >     On 12/22/2009 6:50 AM, David Cole wrote:
>> >
>> >         One way to overcome these things, but still build projects from
>> > source
>> >         code as needed is to use a new feature in CMake 2.8: the
>> >         ExternalProject
>> >         module...
>> >
>> >
>> >     Wow. That could be *really* useful---especially the fact that it
>> > allows
>> >     you to download sources from the web, CVS, svn, etc.  It might be
>> > enough
>> >     to change my mind about maintaining a separate externals archive.
>> > :-)
>> >
>> >
>> >
>> > If it's not enough to change your mind...... let me know what you think
>> > it's
>> > missing.
>> >
>>
>> Here's a use-case: boost-cmake exports buildspace targets to
>> $CMAKE_BINARY_DIR/lib/Exports.cmake.  So you'd want to download,
>> extract, run cmake on the unpacked archive, and only then include() the
>> exported targets...  Does ExternalProject work this way?
>
> It does work that way if you set it up that way.
> So you would have one ExternalProject_Add call to build and install
> boost-cmake... and then a subsequent ExternalProject_Add call to build
> something that depends on it. In this dependent project you would use
> "DEPENDS boost-cmake-proj" to express this dependency. And pass whatever -D
> or prefix information you need to the configure step of this dependent
> project so that it knows where the boost-cmake build is.
> An external project must configure, build and install all the way before any
> of the projects that depend on it even run their first build step.
> It's pretty flexible and customizable. If there's a build step that does not
> do what you want it to by default, you can replace it with your own custom
> step. And you can inject custom steps into the stream of steps that occur by
> default, too.
> HTH,
> David
>
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-- 
Cheers,
Timothy St. Clair