I tried looking for help on the forum, but I had no luck: https://forum.qt.io/topic/80005/how-to-prevent-mingw-qt-5-9-kit-from-adding-std-gnu-11-14-1z-to-compile-flags

Despite setting CONFIG -= c++11 and/or CONFIG -= c++14 (also tried with 17), -std=gnu+11 is always added to the compilation flags.

If I set QMAKE_CXXFLAGS += -std=c++14, it is added, but before the unwanted flag, and is thus overridden. Because of this bug, I cannot compile my code using polymorphic lambdas or something as simple as std::make_unique.

The following test project works with Qt 5.6-5.8, but not with 5.9 https://github.com/KrzaQ/59test