alt Hacker NewsIt doesn’t really work though for generic vectors. If you support not just vec_push but vec_pop as well, then you really do need to store capacity separately or else call realloc way more often than you normally need to.
It doesn’t really work though for generic vectors. If you support not just vec_push but vec_pop as well, then you really do need to store capacity separately or else call realloc way more often than you normally need to.
That may be true, but it may also mean you utilize more memory than you need to. If you aren't shrinking the array when you no longer need previously allocated capacity then you're wasting memory. You could end up with an array of 10 elements and an allocation of 2^10.
The capacity as bit_ceil(len) ensures that at most, half of the allocated space is wasted - excess space is O(n).