[Bug c++/100570] g++ does not suppress bitfield conversion warning even isystem flag is set

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100570

--- Comment #4 from Patrick Palka <ppalka at gcc dot gnu.org> ---
I can't reproduce this.

> g++ -c -x c++ test.cpp -I /usr/local/include/qt5 -I /usr/local/include/qt5/QtCore -g2 -gdwarf-2 -Wall -Wswitch -W"no-deprecated-declarations" -W"empty-body" -Wconversion -W"return-type" -Wparentheses -W"no-format" -Wuninitialized -W"unreachable-code" -W"unused-function" -W"unused-value" -W"unused-variable" -O0 -fno-strict-aliasing -fno-omit-frame-pointer -fpic -fthreadsafe-statics -fexceptions -frtti -std=c++20 -isystem /usr/local/include/qt5

Don't you need to also mark .../qt5/QtCore as a system include directory via
-isystem /usr/local/include/qt5/QtCore?  I suspect that will suppress the
warning you're seeing.