[CMake] Is it possible for a dependee to use the dependency LINKER_FLAGS ?

Fri Aug 8 14:43:35 EDT 2014

On Thu, Aug 7, 2014 at 11:27 AM, Glenn Coombs <glenn.coombs at gmail.com>
wrote:

> I just tried reproducing your 2 examples.  Setup 1 works fine for me with
> no messages about policy CMP0022.  The only way I could get that message
> produced was by omitting the cmake_minimum_required(VERSION 3.0) line.  Are
> you sure you're running the exact same CMakeLists.txt file that you have
> posted here ?
>

Right. I must've messed the copy-paste; I see no cmake warnings either.

>
> For setup 2 I get the same results as you.  CMake seems to insist on
> converting the forward slash into a backwards slash, probably because it
> thinks it is a file path, which totally screws things up.  I suspect this
> is a bug in cmake: adding linker flags like this works for linux because it
> doesn't mess with strings like "-Wl,-Bstatic".  The only workaround I can
> suggest is to set CMAKE_EXE_LINKER_FLAGS:
>
> if (MSVC)
>         set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS}
> /FORCE:Multiple")
> endif()
>

This indeed was my first reaction too, but it's becoming '/FORCE:multiple'
specific.
One other use case would be for a library to require a certain symbol to be
undefined (-u for LD)
I looked through the sources and there's no INTERFACE_LINK_FLAGS appended
when
the target construction is done.

As a work-around I'm setting a variable which is either msvc or gcc
specific.
When I get the linker errors, I append the variable to the LINK_FLAGS of
the erroneous target

>
> which correctly adds the option you want but it will do it for all
> libraries in the current context.  In order to only have it applied to the
> one library you would need to have a separate CMakeLists.txt for that
> library and add the lines above to adjust the CMAKE_EXE_LINKER_FLAGS only
> in that CMakeLists.txt.  Then you would have to do and
> add_subdirectory(special_lib) somewhere in your higher level CMakeLists.txt.
>
> --
> Glenn
>
>
>
> On 3 August 2014 07:43, Adrian M Negreanu <groleo at gmail.com> wrote:
>
>> I've tested this with vs 2013 but a few things makes me think
>> that using target_link_libraries is not for this type of usage.
>>
>> First, for setup 1:
>> ===== CMakeLists.txt ================
>> cmake_minimum_required(VERSION 3.0)
>>
>> add_library(A a.cpp)
>> target_link_libraries(A INTERFACE -custom-flags)
>>
>> add_executable(E e.cpp)
>> target_link_libraries(E A)
>> ###################################
>>
>> Cmake warns me:
>>
>>   CMake Warning (dev) in CMakeLists.txt:
>>   Policy CMP0022 is not set: INTERFACE_LINK_LIBRARIES defines the link
>>   interface.  Run "cmake --help-policy CMP0022" for policy details.  Use
>> the
>>   cmake_policy command to set the policy and suppress this warning.
>>
>>   Target "A" has an INTERFACE_LINK_LIBRARIES property.  This should be
>>   preferred as the source of the link interface for this library but
>> because
>>   CMP0022 is not set CMake is ignoring the property and using the link
>>   implementation as the link interface instead.
>>
>>   INTERFACE_LINK_LIBRARIES:
>>
>>     /FORCE:multiple
>>
>>
>> For setup 2:
>> ===== CMakeLists.txt ================
>> cmake_minimum_required(VERSION 3.0)
>> add_library(A a.cpp)
>> set_target_properties(A PROPERTIES INTERFACE_LINK_LIBRARIES
>> "/FORCE:multiple")
>>
>> add_executable(E e.cpp)
>> target_link_libraries(E A)
>> ###################################
>>
>>
>> Cmake works fine, _but_ "/FORCE:multiple" is seen as a file, which leads
>> to error:
>>
>> 1>------ Build started: Project: ZERO_CHECK, Configuration: Debug Win32
>> ------
>> 2>------ Build started: Project: A, Configuration: Debug Win32 ------
>> 2>  A.vcxproj -> C:\Users\amnegrea\Debug\A.lib
>> 3>------ Build started: Project: E, Configuration: Debug Win32 ------
>> 3>LINK : fatal error LNK1104: cannot open file '\FORCE:multiple.obj'
>> 4>------ Skipped Build: Project: ALL_BUILD, Configuration: Debug Win32
>> ------
>> 4>Project not selected to build for this solution configuration
>> ========== Build: 2 succeeded, 1 failed, 0 up-to-date, 1 skipped
>> ==========
>>
>>
>>
>>
>>
>> On Sat, Aug 2, 2014 at 7:38 PM, Walter Gray <chrysalisx at gmail.com> wrote:
>>
>>> Glen is correct. You should take a look at the docs for interface
>>> modules here:
>>>
>>>
>>> http://www.cmake.org/cmake/help/v3.0/manual/cmake-buildsystem.7.html#interface-libraries
>>>
>>> I also put up some examples of how to do this on github a while back.
>>>
>>> https://github.com/wal-rus/cmake-modules
>>>
>>> Hope that helps! Also for future googling the concept is called Usage
>>> Requirements.
>>>  On Aug 2, 2014 8:11 AM, "Glenn Coombs" <glenn.coombs at gmail.com> wrote:
>>>
>>>> I think that you can use the target_link_libraries command to do this:
>>>>
>>>> add_library(A a.cpp)
>>>> target_link_libraries(A INTERFACE -custom-flags)
>>>>
>>>> --
>>>> Glenn
>>>>
>>>>
>>>>
>>>> On 30 July 2014 16:51, Adrian M Negreanu <groleo at gmail.com> wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> Is it possible to attach a property on a target, and that property
>>>>> to be used whenever the target is used ?
>>>>>
>>>>> ex:
>>>>>
>>>>> add_library(A a.cpp)
>>>>> somehow_attach_LINK_FLAGS(A "--custom-flags")
>>>>>
>>>>> # in a different directory
>>>>> add_executable(E e.cpp)
>>>>> target_link_libraries(E A)
>>>>> # ^---  this would do something similiar to
>>>>> set_target_properties(E PROPERTIES LINK_FLAGS "--custom-flags")
>>>>>
>>>>> For example, to use A:LINK_FLAGS
>>>>>
>>>>> Thanks
>>>>>
>>>>> --
>>>>>
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>>>>
>>>>
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>>>>
>>>> Powered by www.kitware.com
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>>
>>
>> --
>> Regards!
>> http://groleo.wordpress.com
>>
>
>

-- 
Regards!
http://groleo.wordpress.com
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