[CMake] Proposal: extra option PRIVATE for target_link_libraries

[Michael Wild]

On 23. Dec, 2009, at 14:36 , Alexander Neundorf wrote:

> On Wednesday 23 December 2009, Marcel Loose wrote:
>> Hi all,
>> 
>> I suggested this in the quite long thread "third party library
>> dependencies", but it may have been overlooked. Hence, I started a new
>> thread.
>> 
>> Upon (re)reading the Mandriva page
>> http://wiki.mandriva.com/en/Overlinking, I was thinking: maybe the issue
>> of overlinking can be solved more or less the same way as pkg-config
>> does: i.e. by defining private dependencies. This could be an extra
>> option to target_link_libraries.
>> Something like:
>> 
>>  target_link_libraries(mylib public1 public2 PRIVATE private1 private2)
> 
> Assuming that public1 and public2 are libraries also built with cmake, that 
> can be done already today:
> 
> add_library(public1 ...)
> target_link_libraries(public1 private1)
> target_link_libraries(public1 LINK_INTERFACE_LIBRARIES "")
> 
> add_library(public2 ...)
> target_link_libraries(public2 private2)
> target_link_libraries(public2 LINK_INTERFACE_LIBRARIES "")
> 
> install(TARGETS public1 public2 ... EXPORT MyPublicLibs)
> install(EXPORT ...)
> 
> 
> Then later on, when loading these exported targets, you will get what you 
> want. If public1/2 are shared libs, their "link interface" will be empty. If 
> they are static, you will link against everything they have been "linked" 
> against, independent of the LINK_INTERFACE_LIBRARIES (which is used only for 
> shared libs).
> 
> Alex
> 

So, the last step in doing

add_library(public1 ...)
add_library(public2 ...)
target_link_libraries(public2 public1 private1)
target_link_libraries(public2 LINK_INTERFACE_LIBRARIES public1)

is equivalent to

set_target_properties(public2 PROPERTIES LINK_INTERFACE_LIBRARIES "public1")

Am I right?


So, this should definitely go somewhere on the Wiki, that when one creates a project that does an install(EXPORT ...) and provides a XXX-config.cmake file, that one should carefully use target_link_libraries(... LINK_INTERFACE_LIBRARIES ...) to make things play nicely.

This doesn't solve the problem for non-cmake built libraries which are discovered through FindXXX.cmake modules, though.


Michael