[CMake] adding same subdirectory multiple times.

[Michael Wild]

On 11. Mar, 2010, at 9:27 , Mika.Rajala at patria.fi wrote:

> 
> 
> cmake-bounces at cmake.org wrote on 11.03.2010 10:04:42:
> 
>> On 11.03.10 09:56:35, Mika.Rajala at patria.fi wrote:
>>> 
>>> Hi
>>> 
>>> The problem:
>>> 
>>>> From a shared CMakeLists.txt i get the following error when defining a
>>> library target.
>>> Policy CMP0002 is not set: Logival target names must be globally
> unique.
>>> 
>>> 
>>> The situation:
>>> 
>>> Let's assume i have the following cmake files in the following folders
> with
>>> the svn:externals properties.
>>> 
>>> C:\project\CMakeLists.txt
>>> add_subdirectory(ProjectA)
>>> add_subdirectory(ProjectB)
>>> 
>>> C:\project\ProjectA   (svn:externals LibraryA <svn_path_to_libA>)
>>> add_subdirectory(LibraryA)
>>> 
>>> c:\project\ProjectB    (svn:externals LibraryA <svn_path_to_libA>)
>>> add_subdirectory(LibraryA)
>>> 
>>> c:\project\LibraryA
>>> add_library(LibraryA)
>>> 
>>> Thoughts:
>>> 
>>> I don't know if this causes any problem, I tried reading some
>>> documentations but I couldn't figure it out.
>> 
>> Yes it does. The library target is defined multiple times, thats not
>> possible. Each version of "LibraryA/CMakeLists.txt" has to use its own
>> name for LibraryA if you want that directory layout to work. Target
>> names must be globally unique as the error message says.
>> 
>> From a quick glance I see two options:
>> - drop the externals and let the projects depend on a "LibraryA" target
>>  being defined (you need to use the add_subdirectory call for it to the
>>  fron then
>> - find a way to test in LibraryA/CMakeLists.txt wether its under
>>  ProjectA, ProjectB or project and adjust the target name then.
>> 
>> Andreas
>> 
>> --
>> Questionable day.
>> 
>> Ask somebody something.
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> 
> Thanks.
> 
> I'd still like to know if there is a way to handle this like including c++
> header files
> 
> Something like
> 
> if(LibraryA)
>      message(Already included, doing nothing)
> else()
>      <Normal CMakeLists content>
> endif()
> 
> -mika

if(TARGET LibraryA)
  message("Already included, doing nothing")
  return()
endif()
...


You could also use directory properties to set "include-guards".

HTH

Michael