The problem is I am lost in finding the source of the problem.

From what I have read, the problem is that the Mscv compiler does not handle this flag but the MinGW does. I have tried both and both gave me the same error. I have looked at the qmake.conf files in the QT directory, and the Mscv version does not have them.

I am looking on guidance on where and how to find the cause of the error. I have no idea where to look.... Google is not very helpful...

BTW the source code is original from the Github. I have changed nothing. The line where the term occurs is in the bitcoin-qt-win64.pro file.

QMAKE_CXXFLAGS_WARN_ON = -fdiagnostics-show-option -Wall -Wextra -Wformat -Wformat-security -Wno-unused-parameter -Wstack-protector