CONFIG += is ignored?

[Andy Turfer]

I'm new to Qt and am using Qt 5.12 on Linux. I am familiarizing myself with how Qt does things. Something I've noticed it the in my MyProject.pro, the CONFIG +={values} seems to be ignore. For example, I can place this in there:

CONFIG += AAAAAAAAA

yet my project still builds without any errors.

Why is this?

[aha_1980]

@Andy-Turfer what happens if you place valid values there?

[Andy Turfer]

@aha_1980 I'm not sure, which is why I have trying invalid values. CONFIG += C++11 seems to do the same thing as CONFIG += C++17. I'll try to write a small program that uses something C++17 specific.

[SGaist]

Hi and welcome to devnet,

AFAIK, unless you have a feature corresponding to what you put in CONFIG, what you add to it won't change anything.

See Adding New Configuration Features in Qt's documentation.

[Andy Turfer]

@SGaist Thanks - that seems to make sense. I just created a Qt Console application using with the following in my TestConsoleApp.pro:

QT -= gui

CONFIG += c++17 console
CONFIG -= app_bundle
CONFIG += JKFLDJFLKJDSKFJDS
DEFINES += QT_DEPRECATED_WARNINGS

SOURCES += \
        main.cpp

qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

The console application uses std::string_view:

#include <QCoreApplication>
#include <iostream>
#include <string_view>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    std::string_view sv = "ABCD";
    std::cout << sv << std::endl;

    return a.exec();
}

This compiles and runs. If I change C++17 back to the default C++11, the build fails (indicating C++17 is working).

The line with CONFIG += JKFLDJFLKJDSKFJDS does absolutely nothing.

Thanks for the answer, I'll read through the "Adding New Configuration Features" from the docs.

[aha_1980]

@Andy-Turfer which Qt version are you using?

It has been CONFIG+=c++1z forever. c++17 was introduced as alias in 5.12, IIRC.