A result that fits
With `size_t a = 45` and `size_t b = 7`, `(a - b)*2` is 76, while `a - b*2` is 31. Both results fit in `size_t`, so the arithmetic gives the mathematical results. Parentheses change which calculation is performed; they do not change the range the type can represent. section 4.1.1
Numerical overflow occurs when an arithmetic result is outside its type’s representable range. For `size_t`, that range is 0 through `SIZE_MAX`: multiplying two sufficiently large values can produce a mathematical result greater than `SIZE_MAX`. section 4.1.1
TAKEAWAY: Unsigned arithmetic is always well defined, but a `size_t` addition, subtraction, or multiplication gives the mathematical result only when that result is representable. “Well defined” does not mean “always mathematically exact.” section 4.1.1
for (unsigned i = 1; i; ++i) do_something();
for ( signed i = 1; i; ++i) do_something();
!@%STYLE%@!
{"css":"{\"css\": \"font-weight: bold;\"}","target":"[[{\"line\":0,\"ch\":3},{\"line\":0,\"ch\":6}],[{\"line\":1,\"ch\":3},{\"line\":1,\"ch\":6}],[{\"line\":0,\"ch\":8},{\"line\":0,\"ch\":16}],[{\"line\":0,\"ch\":3},{\"line\":0,\"ch\":6}],[{\"line\":1,\"ch\":3},{\"line\":1,\"ch\":6}],[{\"line\":0,\"ch\":10},{\"line\":0,\"ch\":16}],[{\"line\":1,\"ch\":10},{\"line\":1,\"ch\":16}]]"}
!@%STYLE%@!
The two loops differ only in whether `i` is unsigned or signed. That distinction matters when reasoning about arithmetic at the type’s range limit; do not transfer an unsigned-arithmetic guarantee to a signed variable. section 5.7.5
Signed integers require separate care: their treatment raises questions about both overflow and sign representation. In performance-sensitive C code, integer overflow is also a safety concern. Do not trade the obligation to check arithmetic assumptions for a clever optimization. section 5.7.5 section 15.0
