Just to give a more exact solution
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
#include "foo.h"
#pragma GCC diagnostic pop
Also in the above example if you wanna ignore all warnings possible in clang you can use -Weverthing instead!
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Weverything" // clang only
#include "foo.h"
#pragma GCC diagnostic pop