[CMake] Linking archives in a sibling directory

[Raymond Wan]

Hi Michael,


On Thu, Dec 2, 2010 at 01:03, Michael Hertling <mhertling at online.de> wrote:
> On 12/01/2010 08:18 AM, Raymond Wan wrote:
>> Hi all,
>>
>> I'm having a problem understanding how I can link to an archive in
>> another directory which is not a subdirectory. For example:
>>
>> myproj
>>   +-- main
>>     +-- CMakeLists.txt
>>     +-- source files for main program
>>   +-- dir-A
>>     +-- CMakeLists.txt
>>     +-- source files for sub-program A
>>   +-- dir-B
>>     +-- CmakeLists.txt
>>     +-- source files for sub-program B
>
> This error is caused by the fact that the directory "dir-A" is outside
> the "main" directory tree, so dir-A's binary directory would likewise
> be outside main's binary tree, and this is reasonably forbidden when
> configuring "main". You might specify dir-A's binary directory in
> main/CMakeLists.txt explicitly, e.g.:
>
> ADD_SUBDIRECTORY(../dir-A ${CMAKE_CURRENT_BINARY_DIR}/dir-A)
>
> Hence, subprogA_ar will be built within the binary tree's "dir-A".


Ah!  I see now.  I didn't realize I could prepend a path like that.  I
was trying to find some kind of "ADD_DIRECTORY" command which had this
restriction removed.  But then I realized if I'm looking for something
like that, there might be a bigger problem in terms of how I'm
organizing things...


>> myproj
>>   +-- main
>>     +-- CMakeLists.txt
>>     +-- source files for main program
>>     +-- dir-A
>>       +-- source files for sub-program A
>>     +-- dir-B
>>       +-- source files for sub-program B
>>
>>
>> Is this what I should have done??
>
> As an alternative, consider to add a CMakeLists.txt in "myproj"
>
> CMAKE_MINIMUM_REQUIRED(...)
> PROJECT(myproj)
> ADD_SUBDIRECTORY(dir-A)
> ADD_SUBDIRECTORY(dir-B)
> ADD_SUBDIRECTORY(main)
>
> and subsequently, configure this directory instead of "main".


Ah!  I see.  Then is it recommended that this top-level CMakeLists.txt
have just these lines, or should I move the ADD_EXECUTABLE, etc. lines
here as well?  Or is this really "up to me" and there isn't a
suggested paradigm?

I guess I chose my first directory layout because the source in a
directory (i.e., dir-A) can be several dependencies down and it can
even be used by two targets in two different directories.  So, I
figured that keeping them all at the "same directory level" would be
best.  But it seems what you're suggesting here seems better -- never
thought of it; the "myproj" directory has no files in it...just
directories right now...

Thank you for your advice!

Ray