We use a bunch of third party packages (e.g. parts of boost) and, because they typically don't compile without warnings or weird compiler options* we try to isolate them in "trampoline" files or surround the header includes with a bunch of #pragma GCC diagnostic ignored "-Wblahblah"

Some of the errors are way past the parse tree and so they can't be controlled by a pragma diagnostic ignored (e.g. -Wduplicated-branches ). So this option is silently ignored. It would be convenient if GCC could say "Warning: -Wduplicated-branches can't be controlled in a #pragma diagnostic" . (or add support for it, but that's hard :-)

* BTW I'm not implying these warnings are due to crappy programming; typically they result from the wide variety of compilers and C++ standards the library manages to support. I only have to support two compilers on one platform, all in C++17.