align (old code).c

// Align p to a multiple of w bytes
static inline void* align(const void const* p, unsigned char w) {
    return (void*)(((uintptr_t)(p) + (w-1)) & ~(w-1));
}

round_up (new code).c

static inline uintptr_t                                                            
round_up(uintptr_t val, uintptr_t alignment) {                                     
        // Alignment must be a power of two.                                       
        ASSERT3(__builtin_popcount(alignment), ==, 1);                             
        return ((val + (alignment-1)) & ~(alignment-1));              
}