If you are using symbol visibility/exports, then marking the symbol as exported may prevent the linker from removing it if the code is going into a shared library (including static libraries that are built up into a shared library). It's not a trivial topic though, so you would need to do some reading up to get up to speed. Some starting points which may help:
https://cmake.org/cmake/help/latest/policy/CMP0063.html https://cmake.org/cmake/help/latest/module/GenerateExportHeader.html https://gcc.gnu.org/wiki/Visibility On Fri, Jan 20, 2017 at 8:23 AM, Kris Thielemans < kris.f.thielem...@gmail.com> wrote: > Thanks Mike > > The motivation for linking explicitly with the object file was in the PS > at the bottom, although only very brief of course. > > The registry.cxx file has static variables with constructors with side > effects (they add entries to a std:::map that registers "factories"). > Therefore, registry.cxx refers to stuff in mylib, but neither > wonderful_program.cxx nor mylib refers to stuff in registry.cxx. If I stick > registry.cxx into a library (I could have used mylib for instance), the > linker happily removes it from the wonderful_program executable (as it > thinks its an irrelevant object file). Result: the std::map never gets > initialised. The only way (that I know) to fix this is to link explicitly > with registry.o. Then the linker keeps it, hence the variables get > initialised, hence the std::map does. > > This is I believe a relatively standard trick, although I'm not 100% happy > with it. If anyone has a replacement for that, I'd be happy to know (but > it's probably not for the CMake list). > > Hope this clarifies why I need to export registry.cxx (or its object file). > > Kris > > -----Original Message----- > From: Michael Ellery > Sent: 19 January 2017 16:07 > To: Kris Thielemans > Cc: cmake@cmake.org > Subject: Re: [CMake] installing source (or object) files > > I think my initial reaction to installing a source (cxx) file is that you > should install a static library instead (.a) - which is basically what you > are suggesting. Just define a new static library target that includes the > cxx file and install it…should work fine. If there are headers needed to > use that static lib, you install those as well. There is a third type of > library target called OBJECT, but those are usually just for use in the > context of a build and not meant to be installed (if i recall correctly…). > > HTH, > Mike Ellery > > > On Jan 18, 2017, at 11:49 PM, Kris Thielemans wrote: > > > > Hi > > > > I haven’t had any replies to my message below, hopefully because it was > sent at the wrong time of year… So I’m reposting, but with some > clarifications. > > > > I wrote the message about include_flags only. I’ve currently solved > > this by adding a variable > > > > Set(STIR_INCLUDE_DIRS blabla) > > > > in my STIRConfig.cmake.in (which is at > > https://github.com/UCL/UCL-STIR/blob/master/src/cmake/STIRConfig.cmake > > .in) > > > > and tell the user of the library that they have to do > > > > include_directories(${STIR_INCLUDE_DIRS}) > > > > This works but only for include directories, not for other compiler > flags. I’ve currently solved that by putting all (most?) of these in a > STIRConfig.h.in. > > > > I don’t particularly like the include_directories solution however. I > believe CMake’s eport facility is trying to get away from this. Indeed, for > the library, its include path (and other compilation flags) get > automatically exported, so the user doesn’t have to do anything else than > target_link_libraries to inherit all necessary flags. > > > > Also, my current solution relies on exporting the .cxx. It seems safer > to export the object file as that is guaranteed to have been compiled with > the correct flags, but I don’t know how to do that. > > > > I hope my message below makes more sense now. > > > > Thanks > > > > Kris > > From: Kris Thielemans > > Sent: 27 December 2016 16:12 > > To: cmake@cmake.org > > Subject: installing source (or object) files > > > > Hi all > > > > I have a non-standard set-up where I have a library that needs to be > > linked together with some extra source files that contain > > “registries”). So in my CMakeLists.txt I use > > > > Add_executable(wonderful_program wonderful_program.cxx registry.cxx) > > target_link_libraries(wonderful_program mylib) > > > > registry.cxx needs to be compiled with some of my include files. > > > > For that, I added > > > > include_directories(“${PROJECT_SOURCE_DIR}/src/include”) > > > > I guess I could just as well have added > > > > SET_PROPERTY(SOURCE registry.cxx PROPERTY COMPILE_FLAG > > "-I${STIR_INCLUDE_DIR}") > > > > > > This works fine, but now I want to export my library (relocatable). I > > have created a config file etc, added mylib as an install target, > > installed the include files etc. All of that works great for the > > library. However, I have no idea how to install registry.cxx. I could > > just > > > > INSTALL(FILES registry.cxx …) > > > > However, that doesn’t copy the properties of the source files anywhere. > In particular, it means that a “client” doesn’t know what compilation flags > to use. > > > > Any ideas? > > > > Best wishes for 2017! > > > > Kris > > > > PS: The reason that I need registry.cxx is that it contains some > variables that have a funky constructor that initialises some registries > somewhere. > > PS: Full source code is at https://github.com/UCL/STIR > > -- > > > > Powered by www.kitware.com > > > > Please keep messages on-topic and check the CMake FAQ at: > > http://www.cmake.org/Wiki/CMake_FAQ > > > > Kitware offers various services to support the CMake community. For more > information on each offering, please visit: > > > > CMake Support: http://cmake.org/cmake/help/support.html > > CMake Consulting: http://cmake.org/cmake/help/consulting.html > > CMake Training Courses: http://cmake.org/cmake/help/training.html > > > > Visit other Kitware open-source projects at > > http://www.kitware.com/opensource/opensource.html > > > > Follow this link to subscribe/unsubscribe: > > http://public.kitware.com/mailman/listinfo/cmake > > > -- > > Powered by www.kitware.com > > Please keep messages on-topic and check the CMake FAQ at: > http://www.cmake.org/Wiki/CMake_FAQ > > Kitware offers various services to support the CMake community. For more > information on each offering, please visit: > > CMake Support: http://cmake.org/cmake/help/support.html > CMake Consulting: http://cmake.org/cmake/help/consulting.html > CMake Training Courses: http://cmake.org/cmake/help/training.html > > Visit other Kitware open-source projects at http://www.kitware.com/ > opensource/opensource.html > > Follow this link to subscribe/unsubscribe: > http://public.kitware.com/mailman/listinfo/cmake -- Craig Scott Melbourne, Australia https://crascit.com
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