Tell QMake -std=C++17. QMAKE_CXXFLAGS overridden

Question

I use Qt 5.9.1 and all works fine. Except of one little nuisance: it overrides my -std=C++17.

The project:

#CONFIG += c++14 #makes -std=gnu++1y 
#CONFIG += c++17  # is not supported by Qt591
QMAKE_CXXFLAGS += -std=c++17
TARGET = equipment
TEMPLATE = app
SOURCES += ....
....

Compile instructions:

g++ -c -pipe -std=c++17 -g -std=gnu++11 -Wall -W -D_REENTRANT -fPIC
-DQT_DEPRECATED_WARNINGS -DQT_QML_DEBUG -DQT_SERIALPORT_LIB -DQT_CORE_LIB  
-I../app -I/opt/Qt5.9.1/5.9.1/gcc_64/include -I/opt/Qt5.9.1/5.9.1/gcc_64
/include/QtCore -I. -I/opt/Qt5.9.1/5.9.1/gcc_64/mkspecs/linux-g++ 
-o test0.o ../test0.cc

We can see two -std= and the second -std=gnu++11 by QMake overrides mine first -std=c++17.

How can I tell QMake to use `-std=C++17`?

I just read https://forum.qt.io/topic/11565/qmake_cxxflags-overriden/2 : maybe using `QMAKE_CXXFLAGS_WARN_ON` instead of `QMAKE_CXXFLAGS` whould make your flag override the other... — Olivier Sohn, Jul 05 '18 at 17:28
Possible duplicate of [Can't use c++17 features using g++ 7.2 in QtCreator](https://stackoverflow.com/questions/46610996/cant-use-c17-features-using-g-7-2-in-qtcreator) — jonspaceharper, Jul 13 '18 at 23:46

score 3 · Accepted Answer · edited Jul 13 '18 at 23:45

3

Try CONFIG += c++1z and if it doesn't work pass it to compiler with QMAKE_CXXFLAG.

edited Jul 13 '18 at 23:45

jonspaceharper

4,207
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answered Jul 05 '18 at 17:34

Timur Kukharskiy

303
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score 0 · Answer 2 · answered Mar 22 '23 at 23:46

I'm facing a similar problem. But the reason was that pkg-config included the dependency flag of the target library (-std=с++11). For the g++ compiler, the last flag has the highest priority. And qmake adds library flags and their dependencies after yours.

Tell QMake -std=C++17. QMAKE_CXXFLAGS overridden

The project:

Compile instructions:

How can I tell QMake to use -std=C++17?

2 Answers2

How can I tell QMake to use `-std=C++17`?