On 23. Dec, 2009, at 13:28 , Marcel Loose wrote: > On Wed, 2009-12-23 at 13:09 +0100, Michael Wild wrote: >> On 23. Dec, 2009, at 12:08 , 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) >>> >>> This would tell CMake that mylib directly depends on public1 and public2 >>> and should only link in these two libraries when these are shared >>> object libraries; otherwise private1 and private2 would also need to be >>> added on the link line. >>> >>> The big hurdle to take, of course, is to detect in a >>> platform-independent way whether the given library is shared or static. >>> However, a lot of this knowledge is already available in the diverse >>> Modules/Platform macros, so my feeling is that this should be feasible. >>> >>> Best regards, >>> Marcel Loose. >>> >> >> You would also need a PUBLIC keyword, and then require that all >> FindXXX.cmake modules prefix their libraries with PUBLIC and PRIVATE. If >> only the PRIVATE libraries where prefixed, the following would not work if >> A_LIBRARIES contains PRIVATE: >> >> find_package(A) >> find_package(B) >> add_library(C source.c) >> target_link_libraries(C ${A_LIBRARIES} ${B_LIBRARIES}) >> >> Because then all the B_LIBRARIES would be considered to be private "details" >> of the public A_LIBRARIES... Also, there's no way to tell CMake which of the >> private libraries belongs to which of the public libraries. >> >> I think it would be better if a FindXXX.cmake module marked the private >> libraries as a property of the public libraries and then let CMake take it >> from there (although as of now I wouldn't know on what to set the property, >> except if the module created an IMPORTED target for each of the public >> libraries, but that bears the possibility of target name collisions with the >> importing project). >> >> Michael > > Hi Michael, > > I don't think you'll need to prefix the library names with either > PRIVATE_ or PUBLIC_. CMake could figure out whether "public1" and > "public2" are shared or static libraries. If they are shared libraries, > then the libraries marked as private ("private1" and "private2") do not > have to be linked in as well. Otherwise they must also be linked in. I > assume that CMake keeps a list internally, of all dependent targets; the > private libs should only be added to that internal list if the public > libs are static libs. > > I don't completely understand your example. Are you suggesting that > you'll run into trouble if you have a library named "PRIVATE"? I think > name clashes will currently occur as well if I name my library "debug", > "optimized", or "general". > > Maybe, it would be better if the FindXXX modules would handle this. On > the other hand, you then depend on third parties to properly update > their FindXXX modules, or have to rewrite them yourselves :-( > > Best regards, > Marcel Loose. >
No, it won't work. For example, if FindA.cmake does set(A_LIBRARIES /some/path/libA.so PRIVATE /some/other/path/libX.a /some/other/path/libY.a) and FindB.cmake contains # notice that this is a static library! set(B_LIBRARIES /some/path/libB.a) then the call target_link_libraries(C ${A_LIBRARIES} ${B_LIBRARIES}) expands to (wrapped for legibility target_link_libraries(C /some/path/libA.so PRIVATE /some/other/path/libX.a /some/other/path/libY.a /some/path/libB.a) which is different in meaning from target_link_libraries(C ${B_LIBRARIES} ${A_LIBRARIES}) which becomes target_link_libraries(C /some/path/libB.a /some/path/libA.so PRIVATE /some/other/path/libX.a /some/other/path/libY.a) In the first case libB.a becomes marked as PRIVATE of libA.so! Not very nice if you ask me ;-) Michael _______________________________________________ Powered by www.kitware.com Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html Please keep messages on-topic and check the CMake FAQ at: http://www.cmake.org/Wiki/CMake_FAQ Follow this link to subscribe/unsubscribe: http://www.cmake.org/mailman/listinfo/cmake