On Sat, May 20, 2017 at 7:41 PM, Shaheed Haque <srha...@theiet.org> wrote: > Actually, there is one thing about "target CMake"-based KF5 that I > don't quite understand: is there a way to get to the C++ compile flags > needed from CMake? That is, the modern equivalent of Foo_COMPILE_FLAGS > but for target Foo? Even if the general answer is "no", I'm interested > in at least the CMake variables/properties/commands needed to get to > "-fPIC" and "-std=gnu++14". > > I'm aware of the target properties > COMPILE_FLAGS/OPTIONS/DEFINITIONS/OPTIONS as well as > POSITION_INDEPENDENT_CODE and CXX_STANDARD but none of these seem to > be set on targets I have tried. > > Perhaps these are only set if somehow the compiler name etc. is specified? > > Thanks, Shaheed > > On 18 May 2017 at 18:04, Shaheed Haque <srha...@theiet.org> wrote: >> Hi, >> >> On 18 May 2017 at 12:51, Andreas Hartmetz <ahartm...@gmail.com> wrote: >>> On Samstag, 13. Mai 2017 23:48:33 CEST Shaheed Haque wrote: >>>> Hi, >>>> >>>> On 13 May 2017 at 22:04, Sven Brauch <m...@svenbrauch.de> wrote: >>>> > Hi, >>>> > >>>> > On 05/13/2017 06:06 PM, Shaheed Haque wrote: >>>> >> The printed output shows that the variable KF5KIO_INCLUDE_DIRS is >>>> >> not >>>> >> set. In poking around, I see references to a (new-to-me) >>>> >> target-based >>>> > >>>> >> system, and using that like this: >>>> > The question is, why do you need to do that? >>>> >>> The idea with the target based system aka "Modern CMake" is that you say >>> you want to compile against a library, and that is all you have to do. A >>> library requires you to add an include path for its own headers, include >>> paths for headers of one of its dependencies, and link against a bunch >>> of libraries? All covered by target properties. >>> If for some reason (e.g. handover to an external tool) you need those >>> properties, you can still query them. Under enforced names nonetheless, >>> unlike FOO_INCLUDE_DIR or was it FOO_INCLUDE_DIRS? >> >> Ack. The problem from the point of view of an automated tool which starts >> with a component called Foo arises ONLY because the target(s) of Foo are >> called FooFoo and FooBar. CMake does not - AFAICS - allow one to query Foo >> and somehow find FooFoo and FooBar inorder to look up FooFoo_INCLUDE_DIRS >> etc. >> >> >>>> I'm continuing to experiment with trying to build Python bindings for >>>> KF5. As part of that, the SIP tooling creates C++ wrapper code which >>>> must be compiled for each framework, and for that I need to know the >>>> header file directories. So far, I have simply been hardcoding the >>>> needed paths on my own system, but I now want to move to using >>>> standard CMake-based logic instead. >>>> >>>> (In some sense, this might be seen as similar to the stuff that was >>>> added to ECM, but I'm trying for a significantly more automated >>>> approach). >>>> >>>> Also, I am trying to feel my way towards a Pythonic build system for >>>> the KF5 bindings (as, roughly speaking, PyQt seems to be doing): in >>>> other words I'm interested in using CMake as a stepping stone, not the >>>> actual build system. >>>> >>> I would recommend against that unless you really need to have heavy >>> logic in the build system. A build system's main job is to "solve" a >>> dependency tree - that is the difference between a build system and a >>> script that runs the compiler. The dependency tree enables cheap >>> incremental builds and correct parallel builds. Maybe not that important >>> for bindings, admittedly. >>> Your advantage from using Python must be larger than the overhead from >>> doing your own dependency resolution plus the overhead from the CMake- >>> Python interfacing plus the build-related facilities that CMake has and >>> Python doesn't. Or were you considering scons? >>> PyQt may have chosen Python because qmake sucks, and it needs Python >>> anyway, so it avoids any extra dependencies. I know from experience that >>> you really want to avoid extra dependencies in commercial products. >> >> /me nods vigourosly. >> >> I'm not (yet) familair with all the intricacies of the Python build system >> (or CMake for that matter!), but I do see that PyQt has to work quite hard >> to keep its build system working as a Python user might expect. Further, the >> system I am seeking to build has to support more than KF5 (or even KDE). So, >> roughly speaking, the split I am going for is: >> >> - Keep all platform and system independent code in Python >> - Isolate all platform and system independent logic in CMake >> >> As I say, I am feeling my way a bit here, but this seems like a >> philosophically justifiable separation. Oh, and to solve the problem of >> finding the targets, I resorted to parsing the CMake files (!!). I can live >> with that hack precisely because by having the split, users of this code who >> are not using it against KF5 will need to replace this CMake part with their >> own anyway. >> >> (At this point, abstracting CMake away entirely is a minor detail). >> >> Thanks for the helpful remarks. >> >> Shaheed >> >> >> >>>> Thus, I'm after the moral equivalents of: >>>> >>>> Foo_INCLUDE_DIRS >>>> Foo_COMPILE_FLAGS >>>> >>>> Thanks, Shaheed >>>> >>>> > The usual way is to simply call >>>> > >>>> > target_link_libraries(mybinary KF5::KIOCore) >>>> > >>>> > and include paths etc. will be set up for your target automatically. >>>> > >>>> > Best, >>>> > Sven >>> >>> Cheers, >>> Andreas M9
You can easily see how it works in extra-cmake-modules code. Aleix