[CMake] relocatable build directory: howto?

[Dave Abrahams]

on Sat May 05 2012, Michael Wild <themiwi-Re5JQEeQqe8AvxtiuMwx3w-AT-public.gmane.org> wrote:

> On 05/05/2012 07:25 AM, Dave Abrahams wrote:
>> 
>> I need to preserve the built-but-not-yet-installed state of some
>> projects, and the tool I'm driving CMake with moves the result of every
>> build step from a read-write build directory into a readonly cache.  The
>> result is that the generated cmake_install.cmake files no longer work,
>
>> because they are full of absolute paths.  I wrote a simple program to
>> adjust the paths in the cmake_install.cmake files as a postprocessing
>> step, replacing $CWD, where it is found, with a cmake variable.  The
>> only problem: on my Mac, /tmp is a symlink to /private/tmp, and in some
>> scenarios the absolute path in cmake_install.cmake is the short one
>> wheras while $CWD is the long one.  No match :(
>> 
>> I started to write some code to address this problem, but it's getting
>> complex to the point where it seems like "there must be a better way."
>> So I ask: is there?
>> 
>> Thanks in advance,
>> 
>
> I'm afraid that the answer is no. There is the variable
> CMAKE_USE_RELATIVE_PATHS, but that is broken and does not work in
> general. Just out of curiosity: Why do you need to cache the build tree
> in the first place? 

I'm driving CMake with a package installation system (0install) that
doesn't allow for subpackages (it may someday, but that's not supported
as of now).  This system installs packages into a cache.  It's
undesirable to have to build a cmake package twice just to produce its
-dev (on windows, includes import libraries) and -bin (includes
DLLs/so's) incarnations.  The way we deal with that now is to make the
preinstall (built) state a separate 0install package and let 0install
put that in the cache, then come back later and install from that
package.

Which reminds me; it would be awesome if there were a way to get cmake
to clean everything but the leaves in its dependency graph.  IOW, I'd
like to throw out all the .o files after having built libraries.  Is
there a way?

> Would it be enough to "make install DESTDIR=/path/to/cache"?

Only if I want to build twice.

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com