Usage of size_t in C

Question

So I have read other responses here on sololearn and also other platforms like stackoverflow but I'm unable to understand the difference between why size_t is preferred over unsigned int /unsigned long int directly?

Answer 1

i) size_t automatically adjusts(32-bit or 64-bit)
eg. on 32-bit ->it's unsigned int, on 64-bit -> it's unsigned long

ii) Functions like malloc(), sizeof, array indexing expect size_t cuz using unsigned int may cause warnings or overflow on 64-bit systems

iii) C standard library uses size_t, so matching it avoids bug

btw always use size_t for sizes, counts, and indexing, it’s the safest and most portable choice

Answer 2

size_t and unsigned int should be treated differently, even though, under the hood, they're said to be the same

size_t tells the programmer or code reviewer that the variable is used for size calculations or memory traversal (that can't be below 0. negative sizes don't make sense).
This reason is more for readability

size_t also changes its size across different architectures which is useful for portability.
This also tells us that size_t is intended for working with objects in memory; you shouldn't just use size_t for normal variables as it may throw off calculations

size_t: use for working with memory (allocations, lengths, sizes, etc) or traversing through memory (arrays, pointers, etc)

unsigned int: use for working with actual real world data