[CMake] How not to copy a link

[David Cole]

On Fri, Jan 6, 2012 at 10:54 PM, Michael Hertling <mhertling at online.de> wrote:
> On 01/06/2012 07:51 PM, Kevin Burge wrote:
>> Thanks David.  These are external libraries built outside of CMake,
>> without CMake, not imported via any of the import capabilities of cmake,
>> and that need to be installed alongside my CMake built files.  I think
>> I'm just going to do the install with the rename.  Requires me to be
>> more explicit, but, it's not like it changes all that frequently.
>
> Isn't it sufficient to copy such SONAME symlinks as they are, along with
> the actual library files, of course? Having a symlink from the SONAME to
> the library file is a basic mean of the ABI management on platforms with
> advanced - ;-) - support of shared libraries. Besides, these symlinks
> are automatically created by ldconfig when the latter processes the
> directory.
>
> Anyway, w.r.t. your initial question, I'd usually suggest to use the
> GET_FILENAME_COMPONENT(... REALPATH) command on the symlink prior
> to the INSTALL() command, but it seems to not work as expected:
>
> CMAKE_MINIMUM_REQUIRED(VERSION 2.8 FATAL_ERROR)
> PROJECT(P NONE)
> SET(CMAKE_VERBOSE_MAKEFILE ON)
> EXECUTE_PROCESS(COMMAND ${CMAKE_COMMAND} -E
>    touch xyz.dat.0)
> EXECUTE_PROCESS(COMMAND ${CMAKE_COMMAND} -E
>    create_symlink xyz.dat.0 xyz.dat)
> GET_FILENAME_COMPONENT(XYZ xyz.dat REALPATH)
> MESSAGE("XYZ: ${XYZ}")
>
> Due to the documentation of GET_FILENAME_COMPONENT(... REALPATH),
>
> "... the full path with *all* symlinks resolved (REALPATH)."
>
> I'd expect to see
>
> XYZ: .../xyz.dat.0
>
> instead of
>
> XYZ: .../xyz.dat
>
> Do I misunderstand GET_FILENAME_COMPONENT() in respect thereof?
>
> Regards,
>
> Michael
>
>> On 01/06/12 12:45, David Cole wrote:
>>> Have you considered setting the VERSION and SOVERSION target
>>> properties on your libraries instead of doing the symlinks yourself?
>>> CMake will build and install the symlinks automatically for you on
>>> platforms where they are supported if you set these target properties.
>>>
>>> http://www.cmake.org/cmake/help/cmake-2-8-docs.html#prop_tgt:SOVERSION
>>> http://www.cmake.org/cmake/help/cmake-2-8-docs.html#prop_tgt:VERSION
>>>
>>> (Or was that just an example, and you need to do this with other
>>> symlink files that are not simply the version symlinks for a
>>> library...?)
>>>
>>>
>>> HTH,
>>> David
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It works if you use:

  GET_FILENAME_COMPONENT(XYZ ${CMAKE_CURRENT_BINARY_DIR}/xyz.dat REALPATH)

I'm not 100% sure if the behavior is expected to be defined for
non-full paths. Hopefully Brad sees this and chimes in. If not, I'll
try to remember to ask him about it on Monday.


HTH,
David