Difference between i++ and (i)++ in C

i++ and (i)++ behave identically. C 2018 6.5.1 5 says:

A parenthesized expression is a primary expression. Its type and value are identical to those of the unparenthesized expression. It is an lvalue, a function designator, or a void expression if the unparenthesized expression is, respectively, an lvalue, a function designator, or a void expression.

The wording is the same in C 1999.

In your simple example of i++ versus (i)++, there is no difference, as noted in Eric Postpischil's answer.

However, this difference is actually meaningful if you are dereferencing a pointer variable with the * operator and using the increment operator; there is a difference between *p++ and (*p)++.

The former statement dereferences the pointer and then increments the pointer itself; the latter statement dereferences the pointer then increments the dereferenced value.