[CMake] xcode project and static library dependencies

[David Cole]

On Mon, Jan 17, 2011 at 9:02 PM, Nick Kledzik <kledzik at apple.com> wrote:

> On Jan 13, 2011, at 1:57 PM, Bill Hoffman wrote:
> > On 1/13/2011 4:49 PM, Nick Kledzik wrote:
> >> On Jan 13, 2011, at 12:41 PM, Bill Hoffman wrote:
> >>> This is because Xcode provides no way to order static libraries as
> >>> far as I can tell, or to repeat them.   Also, no way to depend on a
> >>> static library or a file directly, forcing the makefile usage.
> >>> This may have changed, so, if you can so native Xcode projects that
> >>> can do the following we can change cmake:
> >>>
> >>> - have a static library show up more than once on a link line
> >> This is unnecessary.  Unlike most unix linkers, the Xcode linker
> >> repeatedly iterators over all archives on the command line.  You
> >> never need to add the same archive more than once on the command
> >> line.
> >>
> > That was not true when I implemented this the first time.  We have a test
> in CMake that counts on library ordering and it failed.
> >>
> >>> - be able to specify the order of static libraries on the link
> >>> line
> >> The order that the libraries appear in the PBXFrameworksBuildPhase is
> >> the order that they are passed to the linker.
> >>
> > OK, sounds good...
> >>
> >>> - be able to relink an executable when a static library that it
> >>> depends on is rebuilt.
> >> This is normal behavior for the Xccde build system.  If one target
> >> depends on the product of another target, the build system follows
> >> the chain and builds everything needed for the target requested to be
> >> built.
> >
> > If you can get all the CMake tests to pass with these changes, I would be
> very happy to get rid of the extra stuff.  It may have changed, but when I
> first did the implementation, it was required to do it the way it is. That
> said, I have not revisited this stuff since Xcode 1.5, so things may have
> changed for the better.
> I have changes that cause cmake to produce an Xcode project in which the
> targets do not have the extra phases, and the dependencies are set up such
> that incremental builds work efficiently!
>
> But I'm having some impedance mismatches between where Xcode want the build
> results to be and where cmake wants them.  Xcode (like many makefiles) has
> the concept of a normal build and an "install" build.  But when cmake runs
> it builds some test programs using the xcodebuild command line, but does not
> specify the "install" action but then expects to find the resulting
> executable in the install location.
>
> I'm sure I could change TryCompileCode() to add "install" to the xcodebuild
> line, but it seems like lots of other cmake scripts will have the same
> expectations.  I playing with trying to get Xcode to always do an "install".
>  I tried creating xcode projects with the initial (not install) locations
> being where cmake wants them, but xcode seems to not do the internal
> dependency analysis properly when the intermediate results are not within
> BUILD_PRODUCTS_DIR.
>
> What is the cmake model for where the results of a build go?
>

Putting the results where the native tool expects them is fine. CMake makes
no guarantees about where build products go. If a native tool has no
expectations, we try to hide build results underneath the "CMakeFiles/"
directories in the build tree to avoid cluttering a developer's view of the
build tree with stuff they mostly don't need to see...

I don't think there are any hard requirements w.r.t. build products
locations. Although where libraries and executables end up is important for
the CMake generated install rules to work.

Feel free to change things around experimentally if that makes it easy to
work with newer Xcode versions. The test suite will very likely tell us if
things have gone awry.


Thanks for your effort on this,
David Cole
Kitware, Inc.



>
> -Nick
>
>
>
>
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