How do I compile my project using C++17?

[lansing]

Hi I want to use some new features of C++17 for my project so I want to add it in the project file. But I don't know where to declare it.

My project file starts something like this

CONFIG += qt

QT += widgets
QT += network

QT_VERSION_WARNING = "WARNING: Linking against Qt version lower than 5.6.1 is likely to cause CLI tools video encoding to crash due to I/O but in Qt."

And then somewhere in the file it has another line mentioning about CONFIG += C++

contains(QMAKE_COMPILER, gcc) {
	QMAKE_CXXFLAGS += -std=c++11
	QMAKE_CXXFLAGS += -Wall
	QMAKE_CXXFLAGS += -Wextra
	QMAKE_CXXFLAGS += -Wredundant-decls
	QMAKE_CXXFLAGS += -Wshadow
	#QMAKE_CXXFLAGS += -Weffc++
	QMAKE_CXXFLAGS += -pedantic

	LIBS += -L$$[QT_INSTALL_LIBS]
} else {
        CONFIG += c++11
}

Where do I need to update it?

[SGaist]

Hi,

You should add CONFIG += c++17 to your .pro file for C++ 17. If you want the support for the latest standard supported by your compiler use "c++latest".

[lansing]

@SGaist

Where do I add it? After the first line or change the one in that else statement?

[SGaist]

If you want to use it unconditionally, you should remove the mentions of C++11 completely and put the CONFiG line before the other changes.

[lansing]

@SGaist

This line also? And change it to c++17?
QMAKE_CXXFLAGS += -std=c++11

[SGaist]

You should check why the gcc flags where modified that way and then see if the c++17 switch from CONFIG fills them in a compatible way. Otherwise, yes you have to replace it.