[CMake] ExternalProject() Question

[David Cole]

On Thu, Dec 17, 2009 at 10:53 AM, Michael Wild <themiwi at gmail.com> wrote:

>
> On 17. Dec, 2009, at 15:01 , David Cole wrote:
>
> > On Thu, Dec 17, 2009 at 3:20 AM, Michael Wild <themiwi at gmail.com> wrote:
> >
> >>
> >> On 16. Dec, 2009, at 20:35 , Michael Jackson wrote:
> >>
> >>> I am intrigued by the "ExternalProject" feature of CMake 2.8. One
> >> question that I have after reading through the Oct 09 "Kitware Source"
> is
> >> this. If I do a "make clean" or "rebuild" are all the "ExternalProjects"
> >> also cleaned/rebuilt? I could make an argument both ways but I was
> curious
> >> what the default was?
> >>>
> >>> One of my projects depends on HDF5, Tiff, Expat and Boost (And Qt
> >> Eventually). Writing directions to get everything downloaded and built
> is
> >> getting to be a pain. Would be simpler to have all that done for the
> user.
> >>>
> >>> Thanks for any comments
> >>> _________________________________________________________
> >>> Mike Jackson                  mike.jackson at bluequartz.net
> >>> BlueQuartz Software                    www.bluequartz.net
> >>> Principal Software Engineer                  Dayton, Ohio
> >>>
> >>
> >> "make clean" behaves a bit strange for me... It seems to remove some of
> the
> >> stamp files, but does not actually perform a "clean" on the external
> >> project, or wipe the extracted sources. For me, this is a bit of a
> problem,
> >> since the PATCH_COMMAND will try to re-apply a patch, which of course
> will
> >> fail. Not sure how to teach CMake to not re-patch a source tree...
> Perhaps
> >> wrap the whole thing in a apply_patch.cmake script which creates its own
> >> stamp in the external source tree and only applies the patch if that
> stamp
> >> does not exist...
> >>
> >>
> > Michael Wild's observations are correct. The "make clean" of the outer
> > project is going to wipe all the stamp files causing all of the steps to
> > re-run again, including downloads and checkouts.
> >
> > Since the patch command is empty by default and 'patch' is not readily
> > available on Windows, the patching stuff is less well tested than the
> rest
> > of the steps.
> >
> > I guess I would be inclined to say that an outer/main-project "make
> clean"
> > ought to default to cleaning the inner/nested/external projects as
> well...
> > but it's not clear to me that there's a reasonable way to implement that
> > quickly and easily. It's certainly worthy of a feature request and some
> > discussion. And whatever the default behavior is, it should probably be
> > controllable by one or more new arguments to the ExternalProject_Add
> > function.
> >
> > Let me know if you have further ideas and suggestions.
> >
> >
> > Thanks,
> > David Cole
>
>
> Also, should a "make clean" really trigger a re-download? What I would like
> to have is a MD5SUM option to ExternalProject_Add. Currently I'm
> implementing this manually with a custom sub-step, but there's no reason it
> shouldn't be in CMake, because it natively implements -E md5sum.



The MD5SUM option is a good idea that we have considered. I'm almost certain
md5 (or something like it) will appear in a future implementation of
ExternalProject_Add.

Ideally, I think "make clean" should destroy all created build products. And
in the case of ExternalProject_Add, the downloaded source is a "build
product." I understand why you would not want to re-download the source...
You could put a *.tar.gz in your source tree and reference it directly
there. You might not want to do that, either, though.

Thanks for the discussion.
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