Yes, but the C standard also allows a realloc() that can never actually succeed in growing the allocation. The probability by which a given allocation pattern

Yes, but the C standard also allows a realloc() that can never actually succeed in growing the allocation. The probability by which a given allocation pattern is likely to result in a successful growing realloc() seems like a pretty big design choice. Do you leave space after allocations for them to grow? Do you have power-of-2 size-based tables with an allocation bitmap? If so, what sizes? Etc.