El dimarts, 23 de maig de 2017, a les 2:04:54 CEST, Aleix Pol va escriure: > 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.
As far as i understand he wants to know what Qt5::Core actually expands to so he can pass it to some other tool. Cheers, Albert > > Aleix
