I hate using languages that only have signed integers. Using integers that can’t be negative fits many problems nicely and avoids the edge case of having to check for negative.
The so-called "unsigned" integers of C are integer residues, where each value can be interpreted either as both positive and negative or as neither positive nor negative. In any case no "unsigned" value can be said to be non-negative.
You have to go back to languages not contaminated by C, like Ada, to find true non-negative integers among the primitive data types.
In C++, it is possible to define a non-negative integer type, which can have good performance if you implement its operations in assembly language.
However I am not aware of an open-source library including such a type.
And - yes, there are very important use cases for unsigned/modulo-2n/wraparound values. But sizes of data structures are generally _not_ one of those use cases. The fact that the size is non-negative does not mean that the type should be unsigned. You should still be able to, say, subtract sizes and get a signed value which may be negative.
No, signed wraparound is undefined behavior in C, whereas unsigneds are defined to wraparound. If you use -ftrapv, signed wraparound is an immediate abort().
While C like in many other places fails to define the correct behavior to avoid shaming the processor or compiler makers that fail to provide it, there are only 2 correct behaviors on overflows and underflows, like when incrementing the biggest number or decrementing the smallest number.
Both for signed integers and for non-negative integers, the 2 alternatives of correct behavior on overflows and underflows is to either generate exceptions or to saturate the result to the biggest or smallest representable number.
Wraparound is the correct behavior for integer residues, which are a distinct data type from either signed integers or non-negative integers.
While some people criticize C for making easy for careless programmers to make certain kinds of bugs, like access outside bounds, those are easily mitigated by using appropriate compiler options.
For me a much more serious defect of C is this confusion promoted by it in the heads of most programmers, who do not understand which are the fundamental integer types and which are the correct conversions between them, because C uses "unsigned" instead of at least 3 distinct types that it does not have, bit strings, integer residues and non-negative integers. More rarely, "unsigned" is used for other 2 types that are missing, binary polynomials and binary polynomial residues. All these 5 types must be primitive types in a programming language because all modern processors implement in hardware distinct operations for all 5 types, which can be accessed only through assembly language when these types are missing.
They do. The code:
unsigned x;
unsigned y = -x;