Nothing I do seems to affect the warnings produced in the Compile Output (and thus Issues) panes when I clean all, run qmake, and run.
QMAKE_CXXFLAGS is already the right (and only) way. You need to check the compile output, if the flags are really passed to the compiler - because the compiler generates the warnings.
Turning off the ClangCodeModel (Qt Creator>About Plugins...) kills off the inline warnings in the source editor, but has no other obvious effects.
And that's exactly what I wrote in my post yesterday. If you want to keep the inline annotations, you have to enable Clang again and then modify the settings in Tools > Options > C++ > Code Model > Clang Code Model.
Modifying the 'Diagnostic Configuration' (Custom Settings on the Analyzer Configuration, reached from Analyze>Clang Tidy and Clazy...) and files to be analyzed removes/add warnings as expected when running the analyzer, but has no effect on the inline warnings in the source editor.
And that's expected, as it only influences the static analyzer you can call by Analyze > Clang Tidy and Clazy...
So, to keep it short:Compiler warnings are configured with QMAKE_CXXFLAGS Inline annotations are configured with Tools > Options > C++ > Code Model > Clang Code Model
Does that help you?
You can always change that The analyzer is thought to bring up any issue you code may have, much more pedandic than a compiler does. That's the whole point of an analyzer.
'Weverything' is a page about how this is a terrible switch to use on a regular basis. It's the default setting for the analyzer.