CODEWITHSUNDEEP
c++qtgccc++11cross-platform
IAE
IAE

Reputation: 2243

How to Program C++11 Using Qt5?

I'm getting ready to program a cross-platform project with my friend. We decided on using Qt and gcc as our IDE and toolchain respectively. He works on Linux, I work on Windows.

However, gcc on Linux isn't necessarily gcc on Windows. More specifically, Qt on Windows installs mingw with gcc 4.4 and my friend has gcc 4.7. So I tried getting a more recent gcc version for windows.

My current version of Qt is 5 and using gcc 4.7 downloaded and installed from this site: http://www.equation.com/servlet/equation.cmd?fa=fortran

I installed it in C:\QtSDK\mingw and simply overrode all the files existing from the Qt installation. I figured that I wouldn't have to reconfigure anything in Qt if I just took the short route.

However, even using the compiler flags:

QMAKE_CXXFLAGS += -std=c++0x (Qt 4.7)

and

CONFIG   += c++11 (Qt5)

the IDE or toolchain fails to compile a simple range-based for loop:

int main(int argc, char *argv[])
{
    int my_array[5] = {1, 2, 3, 4, 5};
    for (auto x : my_array)
        std::cout << x << std::endl;

    return 0;
}

or initializer-lists:

int main(int argc, char *argv[])
{
    QVector<int> testsData { 1, 2, 10, 42, 50, 123  };
    QStringList options = { QLatin1String("foo"), QLatin1String("bar")  };

    return 0;
}

However, looking at the implementation details of gcc 4.7, both of these features- and more- should be readily available.

Has anyone else tried to use gcc and Qt for Windows? If so, how did you get it to work? I would like a solution using gcc 4.6 or 4.7, but will settle for less if it is not at all possible.

Alternatively, is there a dev environment for Linux and Windows that makes use of C++11 features? I would also settle for something besides Qt if it just works...

I used the sources:

C++0x in Qt (Qt 4.7-4.8)

C++11 in Qt5

Upvotes: 16

Views: 17407

Answers (2)

Zingam
Zingam

Reputation: 4626

UPDATE:

According to this link: https://wiki.qt.io/How_to_use_C%2B%2B11_in_your_Qt_Projects

It is now possible to just do this:

CONFIG += c++11

or

CONFIG += c++14

Also the upcomming Qt 5.7 WILL REQUIRE C++11 compiler by default and will drop support for older non-C++11 compiler.

Older UPDATE:

To enable C++11 - GCC 4.7 and newer is required:

qmake build system: 

QMAKE_CXXFLAGS += -std=c++11

qbs build system:

cpp.cxxLanguageVersion: "c++11"

To enable C++14 - GCC 4.9 and newer is required:

qmake build system: 

QMAKE_CXXFLAGS += -std=c++14

qbs build system:

cpp.cxxLanguageVersion: "c++14"

NOTE: Please note that "c++11", "c++14" etc. are case sensitive.

Obsolete version:

qbs build system:

cpp.cxxFlags: "-std=c++11"
cpp.cxxFlags: "-std=c++14"

Older version:

GCC 4.7 is now recommended for Qt5. With GCC 4.7 you can use QMAKE_CXXFLAGS += -std=c++11

Edit: With GCC 4.9 it is now possible to enable C++14 by passing this flag: QMAKE_CXXFLAGS += -std=c+11

Upvotes: 10

Oipo
Oipo

Reputation: 158

QMAKE_CXXFLAGS += -std=c++0x

Results in an error because you're not using the MinGW compiler. "D9002: Ignoring unknown option -std=c++0x" is an error from the MSVC compiler.

In QtCreator, go to the projects tab(on the left) and change the toolchain you're using. If it hasn't auto-detected MinGW, you're going to have to add it yourself by clicking on the manage button.

Upvotes: 13

Related Questions