[CMake] ExternalProject: avoiding rebuilds

[Ben Medina]

John is right. The external project may be at the bottom of a chain of
(my own) project dependencies. I need to preserve the ability to
easily rebuild just my projects (and their dependencies), not external
projects. Think of ExternalProject as a replacement for pre-built
libraries, and you'll see where I'm coming from.

Perhaps I need to file a feature request on Mantis.

On Sat, Sep 24, 2011 at 2:32 AM, John Drescher <drescherjm at gmail.com> wrote:
> On Sat, Sep 24, 2011 at 4:11 AM, Rolf Eike Beer <eike at sf-mail.de> wrote:
>> Am Freitag, 23. September 2011, 16:26:46 schrieb Ben Medina:
>>> Hello all,
>>>
>>> I'm trying to adopt greater usage of ExternalProject in my project.
>>> One problem I'd like to resolve is spurious rebuilds of external
>>> projects.
>>
>> [...]
>>
>>> This works great: building "test" first untars the CLAPACK source and
>>> builds it, as expected. However, if I rebuild test (i.e. in Visual
>>> Studio, right-click on test and rebuild), then the CLAPACK tarball get
>>> extracted *again*, and a full rebuild of CLAPACK happens. I'd expect
>>> that, unless the tarball is changed, a rebuild of the external project
>>> is a no-op.
>>>
>>> Is there a way to achieve my desired behavior?
>>
>> Yes, use the correct option. Rebuild means "rebuild this target and all of
>> it's dependencies". There is a different option, something like "rebuild only
>> this target". Just use this one.
>>
>
> That may be difficult in practice. I mean I typically have 20 to 40
> targets in my projects and sometimes I would want them all rebuilt.
> However I there is a batch build option in Visual Studio that can be
> used for that. In this case you check which targets you want built so
> you can click select all and then uncheck the external project.
>
> John
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