[CMake] find_package and INTERFACE targets in 3.0

[Hendrik Sattler]

Hi,

for DLLs, the .lib part has it's own property IMPORTED_IMPLIB.

This is already the case for older versions of CMake but at least the Qt4 find module makes no use of it.

In our own project, we use global imported targets with dll and import lib set (and other properties like includes) and use it on Windows to copy the dlls to the target location with a generator expression and post-build.

I guess on Windows, BundleUtilities could also be simplified if that was done consistently.

On all platforms it's rather complicated to find out if a .lib/.so is static or shared. IMHO this should be solved by a function that module writers can use, either on a CMake module or integrated.
So currently, you can either guess or use UNKNOWN.

Regards,

HS


On 19. Juli 2014 05:13:13 MESZ, Walter Gray <chrysalisx at gmail.com> wrote:
>Thanks Nils!
>The examples in the git repo are particularly helpful.  It seems that
>in 
>all of the examples, the library type is being set to UNKNOWN.  Is
>there 
>a reason for this? It seems that STATIC would be more suitable for most
>
>of those, though the wording in the docs for IMPORTED_LOCATION [1]
>makes 
>it seem like maybe for STATIC's it's just the directory and not the 
>actual .lib file.  I notice cmake doesn't seem to have any way to track
>
>DLLs or dylibs.  Is there some recommended way of dealing with
>importing 
>shared libraries? The QT4 module was my best bet but it doesn't seem to
>
>touch the .dlls at all.  I tried writing some of my own for shared 
>libraries like SDL2, I noticed that add_libraries(SHARED IMPORTED) does
>
>not seem to work as  I expected.  An example for Windows(from memory, 
>I'll update with the real run outputs on Monday when I'm back at the 
>office):
>
>add_library(SDL2::SDL2 SHARED IMPORTED GLOBAL)
>set_target_properties(SDL2::SDL2 PROPERTIES
>     INTERFACE_LINK_LIBRARIES 
>"${SDL_ROOT_DIR}/lib/SDL2main.lib";"${SDL_ROOT_DIR}/lib/SDL2.lib"
>     INTERFACE_INCLUDE_DIRECTORIES "${SDL_ROOT_DIR}/include"
>     IMPORTED_LOCATION "${SDL_ROOT_DIR}/lib/SDL2.dll"
>)
>
>According to the docs for IMPORTED_LOCATION [1], for shared libraries
>on 
>DLL platforms, it should point to the DLL part of the library. When I 
>add the SDL2::SDL2 to my main target, it compiles & generates but when
>I 
>run the resulting visual studio project it results in link errors with 
>(and this is the part I'm not sure about - again, more concrete detail 
>on Monday) SDL2-NOTFOUND.o and SDL2::SDL2
>I suspect I'm using INTERFACE_LINK_LIBRARIES in not quite the right
>way, 
>but those *are* the public .lib files. When I get back on Monday I'll 
>try a few different approaches based on what I saw in some of the 
>modules, namely making sub-libraries with UNKNOWN and IMPORTED_LOCATION
>
>set for all the actual .lib files, and just directly setting
>LINK_LIBRARIES
>
>[1] 
>http://www.cmake.org/cmake/help/git-master/prop_tgt/IMPORTED_LOCATION.html
>
>On 7/18/2014 5:23 AM, Nils Gladitz wrote:
>> On 07/18/2014 05:00 AM, Walter Gray wrote:
>>> Hi list!
>>>
>>> I'm a big fan of the new INTERFACE targets & target usage
>requirements,
>>> but none of the provided Find<package>.cmake files seem to take
>>> advantage of the new paradigm.  Checking the wiki, the old
>>> Find<package>.cmake seem to be deprecated, with most of the
>information
>>> on authoring new packages assuming that you are the developer of the
>>> module, not the consumer. What is the recommended way to deal with
>>> packages that don't provide these config files? I'll happily write
>my
>>> own Find<package>.cmake files, however that approach seems
>deprecated
>>> and I haven't found any good examples of find modules that define
>IMPORT
>>> or INTERFACE targets instead of the older method of setting a bunch
>of
>>> <package>_xxx variables.
>>
>> There are a few modules that use imported targets in 3.0 and a few 
>> more were updated in master.
>>
>> I see e.g. FindGLUT, FindQt4, FindGTK2, FindZLIB, FindOpenGL and 
>> FindGLEW making use of imported targets in master[1].
>>
>> [2] documents how to write find modules and includes an example with 
>> IMPORTED targets.
>>
>> Nils
>>
>> [1] 
>>
>http://cmake.org/gitweb?p=cmake.git;a=tree;f=Modules;h=5d17682cb231f119b677ce67d804852d3be6d46f;hb=HEAD
>>
>> [2] 
>>
>http://www.cmake.org/cmake/help/git-master/manual/cmake-developer.7.html#find-modules