error: C2057: expected constant expression



  • I'm trying to build a project orignally made on top of mingw but now we need to switch to MSVC++ (because a specific debugging library only supports that) but to my surprise, compiling that code even on new C++ version/Qt result in the error:

    error: C2057: expected constant expression
    

    The error is not part of my own source code rather Qt itself, from qmetatype.h header, so I have no idea how fix. I assumed it was missing C++11 flag, so I added CONFIG += c++11 nothing changed. Then I tried to more specific and added QMAKE_CXXFLAGS += /std:c++14 to .pro file. Same error. The line of error is:

    struct CapabilitiesImpl<T, std::random_access_iterator_tag>
    { enum { IteratorCapabilities = RandomAccessCapability | BiDirectionalCapability | ForwardCapability }; };
    

    NOTE: Since I was getting cl not found error, I do star the Qt creator from a bat file like this:

    call "C:\Program Files (x86)\Microsoft Visual
    Studio\2017\Community\VC\Auxiliary\Build\vcvarsall.bat" x86
    "C:\Qt-MSVC\Qt5.7.1\Tools\QtCreator\bin\qtcreator.exe"
    

    How can I fix that?

    EDIT

    Complete error message (the error is the same, with another Qt version I've tried, to see if anything changes):

    C:\Qt-MSVC\Qt5.5.0\5.5\msvc2013\include\QtCore\qmetatype.h:944: see
    reference to class template instantiation
    'QtMetaTypePrivate::CapabilitiesImpl<QList<QVariant>,std::random_access_iterator_tag>'
    being compiled
    C:\Qt-MSVC\Qt5.5.0\5.5\msvc2013\include\QtCore\qmetatype.h:1015: see
    reference to class template instantiation
    'QtMetaTypePrivate::ContainerAPI<T>' being compiled with [
    T=QVariantList ] C:\Qt-MSVC\Qt5.5.0\5.5\msvc2013\include\QtCore\qvariant.h:711: see
    reference to function template instantiation
    'QtMetaTypePrivate::QSequentialIterableImpl::QSequentialIterableImpl<QVariantList>(const
    T *)' being compiled with [
    T=QVariantList ]


  • Qt Champions 2017

    That piece of code is quite correct. What is the complete error (with paths, lines and such)?



  • @kshegunov check out the post update



  • @kshegunov cl is this compiler: C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.12.25827\bin\Hostx86\x86\cl.exe is this the correct one, meant to be used with Qt 5.7.1?



  • @Dr.-No
    I see reference to 2 Qt versions in your post Qt 5.7.1 in your text and Qt 5.5.0 ???
    if you look here you will see that Qt 5.5 does not support the Vs 2017 compiler yet same for Qt. 5.7.1. maybe this is the issue?
    If you use the Vs 2017 IDE maybe you can set set the target to a lower one if you have that one installed, don't know if you can do that using Qt Creator to build though.



  • @kenchan I've tried a older version, 5.5.0 just to see if it could work. The error messages edited on my post (part of update) I copied from there. Hence the two diferente versions. But it did not work with either version and result in same error.



  • @Dr.-No well yes, but the higher compiler version might still be the issue in both cases.
    if you scroll to the bottom of the linked page i gave you it shows the compatible tools for each Qt 5 version.



  • @kenchan So for Qt 5.7.1, the cl is Windows-Windows_10-x86-MSVC2015 I must use this visual studio 2015, right?

    I've tried it already, download a 6gb isntallation and change my bat to the following:

    call "C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat" x86
    "C:\Qt-MSVC\Qt5.7.1\Tools\QtCreator\bin\qtcreator.exe"
    
    and I get the same error...
    

  • Qt Champions 2017

    I think you're doing the thing backwards.
    See what visual studio you already have (from the first post it seems VS2017- C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\...), then from the Qt maintenance tool select a Qt version that provides you a binary distribution for that compiler, i.e. Qt >= 5.9 msvc2017-x86 and install it, possibly install the 64 bit binaries msvc2017-x86_x64 as well.
    Then start Qt Creator (no need for call ....) and configure the kit for that Qt version and this compiler.
    To get the debugger you will also need to install CDB from MS debugging tools package.



  • @kshegunov I had VS 2017 instealled already before I need to use MSVC++ compiler with Qt. I was using mingw before but I needed to switch to MSVC++ because I have to use a debugging library that only supports MSVC++ debugg symbols. So I installed Qt with MSVC++ when I went to compile, that error begun. I use call to call the vcvarsall.bat file within my batch script, without the bat doesn't work.


  • Qt Champions 2017

    @Dr.-No said in error: C2057: expected constant expression:

    So I installed Qt with MSVC++

    Please explain exactly what you did. There's no Qt with MSVC, there're a number of distributions of the Qt library compiled with different versions of the MS compiler, and what compiler you have will govern which exact distribution of Qt you will need.

    I use call to call the vcvarsall.bat file within my batch script, without the bat doesn't work.

    You can start Qt Creator without ever needing to have an installed compiler. I don't understand why you call the bat script before starting the IDE. What you need is, as I wrote, to configure the toolchain for your compiler, not start the IDE with the visual studio environment.



  • This post is deleted!


  • @kshegunov I downloaded the Qt Creator from this link, installed, opened my project but when I went to compile I got a cl not found error. So I search on google about the error and found that I should run vcvarsall.bat x86 to set up the needed varialbles. I did that and went to compile again, this time, the cl error was gone but then I got the error, title of this thread. Does make sense to configure the toolchain within the IDE but it didn't work. In fact, I saw alot of people running that script before using Qt Creator IDE, hence the need of this bat.


  • Qt Champions 2017

    @Dr.-No said in error: C2057: expected constant expression:

    In fact, I saw alot of people running that script before using Qt Creator IDE, hence the need of this bat.

    I haven't seen or done that, it may work or not, can't say. What I usually do is follow the Qt Creator manual on configuring the compilers and just put the VC init script in the proper box, that is if creator has failed to detect the compiler automatically ...



  • @kshegunov Qt doesn't fail to detect the compiler but it give the cl command not found error, like this: https://stackoverflow.com/questions/8800361/cl-is-not-recognized-as-an-internal-or-external-command

    The only thing which makes the error go away was that VS batch script to set up the proper paths in the system environment's variables.



  • @Dr.-No So is everything now good to go for you then?



  • @kenchan No. I'm with same error... I solved the cl error before create this thread. Once this compiled, I got expected constant expression error.



  • @Dr.-No Oh dear :-(.
    OK so just to clarify where you are now when you get this error...
    which Qt are you now building against?
    which version of Visual Studio are you now building with?
    are you using the QT Creator IDE to build the project?
    are you using Visual Studio IDE to build the project?



  • @kenchan This is really bad, I have no idea why I'm getting this error. :( I'm downloading 5.10.1 to see if it works. Hope it's something has been fixed.

    which Qt are you now building against?

    Qt creator 4.2.0 and Qt 5.7.1

    which version of Visual Studio are you now building with?

    Visual studio community 2017

    are you using the QT Creator IDE to build the project?

    yes, as mentioned, version 4.2.0

    are you using Visual Studio IDE to build the project?

    nope... as it Qt project (written using mingw) I have only used Qt creator IDE.



  • @Dr.-No Thank you for clarifying that :-). Please post back here the results when using Qt 5.10.1.
    I might have a Qt 5.7.1 around here somewhere :-)



  • @kenchan on the "issues" window within Qt Creator IDE, the error is:

    C:\Qt-MSVC\Qt5.7.1\5.7\msvc2015\include\QtCore\qmetatype.h:945: error: expected constant expression
    

    looking in the compiler output window, I can see those erros too:

    qmetatype.h:944: see
    reference to class template instantiation
    'QtMetaTypePrivate::CapabilitiesImpl<QList<QVariant>,std::random_access_iterator_tag>'
    being compiled
    qmetatype.h:1015: see
    reference to class template instantiation
    'QtMetaTypePrivate::ContainerAPI<T>' being compiled with [
    T=QVariantList ] qvariant.h:711: see
    reference to function template instantiation
    'QtMetaTypePrivate::QSequentialIterableImpl::QSequentialIterableImpl<QVariantList>(const
    T *)' being compiled with [
    T=QVariantList ]
    

    Soon as I try Qt 5.10.1 I'll post the results here.

    EDIT

    This is the line of error qmetatype.h:945:

    { enum { IteratorCapabilities = RandomAccessCapability | BiDirectionalCapability | ForwardCapability }; };
    

    from:

    struct CapabilitiesImpl<T, std::random_access_iterator_tag>
    { enum { IteratorCapabilities = RandomAccessCapability | BiDirectionalCapability | ForwardCapability }; };
    


  • @Dr.-No Hello again.
    I had the same Qt package you have and hacked a kit to use the Vs 2017 compiler (v19.13.26129).
    I built a simple widget project with a QMainWindow, did not see any issues.
    I found this old bug report which looks relevant to the issue you saw.
    I added the code to reproduce that in my test app but still did not see any issues when compiling...
    Not sure what more I can do to help you with on that one :-(.
    wishing you Good Luck with Qt 5.10.1


  • Qt Champions 2017

    As I said this line is valid C++, it doesn't even require anything c++11 related.
    I continue to believe that the error is cause by a misconfiguration of the IDE, which you should fix by configuring the kit (i.e. compiler and Qt distribution). Information is aplenty - reading the creator manual (sourced in previous post) and searching the forums here should be just enough.



  • @kenchan So I was trying luck with Qt 5.10.1. With mingw32 it compiled fine (the project was originally written with mingw32). But with both MSVC2015 and MS2017 I got that error. I haven't change a single line in that source code. It's the exact same source code but with MSVC it give that error. I need to use that compiler because the debugging library I mentioned which only works with MSVC compiler.



  • @kshegunov I'm trying to find the source of misconfiguration which I also believe is the reason of the error. Without running the vcvarsall.bat bar, the compilation with MSVC fail to find the rc executable. All the compilers are properly detected by Qt Creator IDE but it fails to compile, for example, didn't find rc or cl executable. I don't know where check... if it's a PATH missing. I've removed VS2015 affraid of some conflict with VC2017 remove all but the Qt 5.10. And nothing Works.


  • Qt Champions 2017

    Hi @Dr.-No

    We had some requests with missing cl.exe here in the forum (you could search for them), and there is e.g. https://bugreports.qt.io/browse/QTCREATORBUG-17474 (but maybe more).

    In short: QtCreator runs the vcvarsXX.bat also, but in some setups this takes very long and times out. There are also solutions out there which hardcode the paths in the bat file that are determined by registry calls otherwise. You could do this too, if you know what you are doing ;)

    In any case, the compiler has to match the Qt version and the path to the compiler must be correct. I assume that there is something wrong in your setup, and maybe (most likely) hte error C2057 is just a result of that.

    Regards


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