CWG2855 Undefined behavior in postfix increment

Author: burblebee

source/expressions.tex

@@ -3764,7 +3764,7 @@
 An operand with volatile-qualified type is deprecated;
 see~\ref{depr.volatile.type}.
 The value of the operand object is modified\iref{defns.access}
-by adding \tcode{1} to it.
+as if it were the operand of the prefix \tcode{++} operator\iref{expr.pre.incr}.
 The
 \indextext{value computation}%
 value computation of the \tcode{++} expression is sequenced before the
@@ -3779,11 +3779,6 @@
 \end{note}
 The result is a prvalue. The type of the result is the cv-unqualified
 version of the type of the operand.
-If the operand is a bit-field that cannot represent the incremented value, the
-resulting value of the bit-field is
-\impldefplain{value of bit-field that cannot represent!incremented value}.
-See also~\ref{expr.add}
-and~\ref{expr.ass}.
 
 \pnum
 \indextext{expression!decrement}%
@@ -4785,32 +4780,16 @@
 \pnum
 \indextext{expression!increment}%
 \indextext{expression!decrement}%
-The operand of prefix \tcode{++}
 \indextext{operator!increment}%
+\indextext{operator!decrement}%
 \indextext{prefix \tcode{++}}%
-is modified\iref{defns.access} by adding \tcode{1}.
 \indextext{prefix \tcode{--}}%
-The operand shall be a modifiable lvalue. The type of the operand shall
-be an arithmetic type other than \cv{}~\tcode{bool},
-or a pointer to a completely-defined object type.
+The operand of prefix \tcode{++} or \tcode{--}
+shall not be of type \cv{}~\tcode{bool}.
 An operand with volatile-qualified type is deprecated;
 see~\ref{depr.volatile.type}.
-The result is the updated operand; it is an lvalue, and it is a
-bit-field if the operand is a bit-field.
-The expression \tcode{++x} is equivalent to \tcode{x+=1}.
-\indextext{operator!\idxcode{+=}}%
-\begin{note}
-See the discussions of addition\iref{expr.add} and assignment
-operators\iref{expr.ass} for information on conversions.
-\end{note}
-
-\pnum
-The operand of prefix
-\indextext{operator!decrement}%
-\tcode{--} is modified\iref{defns.access} by subtracting \tcode{1}.
-The requirements on the operand of prefix
-\tcode{--} and the properties of its result are otherwise the same as
-those of prefix \tcode{++}.
+The expression \tcode{++x} is otherwise equivalent to \tcode{x+=1} and
+the expression \tcode{--x} is otherwise equivalent to \tcode{x-=1}\iref{expr.ass}.
 \begin{note}
 For postfix increment and decrement, see~\ref{expr.post.incr}.
 \end{note}