On Mon, May 22, 2017 at 7:54 PM, Shaheed Haque <srha...@theiet.org> wrote: > On 21 May 2017 at 22:27, Aleix Pol <aleix...@kde.org> wrote: >> 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. > > I don't think it is quite so simple. First, for "-std=gnu++14",the ECM > code just hardcodes it (with a comment that hints at difficulties > extracting this value). Second, it grabs INTERFACE_COMPILE_DEFINITIONS > and INTERFACE_COMPILE_OPTIONS of which the latter seems to be needed > in order to get stuff from come KF5 cmake file which set -fexception > (in some case, for example). > > But what sets "-fPIC"? It seems to be inherited in some way from > Qt5::Core INTERFACE_COMPILE_OPTIONS, but how can I get to that > programmatically? > > Thanks, Shaheed > >> Aleix
I don't understand what you're trying to do. You are not supposed to change the definitions Qt5::Core suggests to the compiler. Aleix