7 Expressions [expr]

7.6 Compound expressions [expr.compound]

7.6.2 Unary expressions [expr.unary]

7.6.2.3 Increment and decrement [expr.pre.incr]

The operand of prefix ++ or -- shall not be of type cv bool.
An operand with volatile-qualified type is deprecated; see [depr.volatile.type].
The expression ++x is otherwise equivalent to x+=1 and the expression --x is otherwise equivalent to x-=1 ([expr.ass]).
[Note 1: 
For postfix increment and decrement, see [expr.post.incr].
— end note]