Function keep_memory

external/catch.hpp:6483–6485

#if defined(__GNUC__) || defined(__clang__)
        template <typename T>
        inline void keep_memory(T* p) {
            asm volatile("" : : "g"(p) : "memory");
        }
        inline void keep_memory() {
            asm volatile("" : : : "memory");
        }