C/C++ performance magic functions (prevent optimization)

magic.h

/**
 * Those functions are related to: https://www.youtube.com/watch?v=nXaxk27zwlk&t=2446s
 *
 * They are used to allow to benchmark functions with -O3 that would otherwise be removed because it is unused.
 *
 * escape(&object) prevents object to be optimized out 
 *    "This ASM code has some unknowable side effects and possibly stored the pointer globally"
 * clobber() tells the compiler some asm might be reading the whole memory
 *    "This ASM code could probably read/write to all memory" => observe all memory
 */

void escape(void* p) {
    asm volatile("" : : "g"(p) : "memory");
}

void clobber() {
    asm volatile("" : : : "memory");
}

Example:

void benchmark() {
    std::vector<int> v;
    v.reserve(1);
    escape(&v.data());
    v.push_back(42);
    clobber();
}