INT32-C. Ensure that integer operations do not result in an overflow

Integer values used in any of the the following ways must be guaranteed correct:

as an array index
in any pointer arithmetic
as a length or size of an object
as the bound of an array (for example, a loop counter)
in security critical code

Most integer operations can result in overflow if the resulting value cannot be represented by the underlying representation of the integer. The following table indicates which operators can result in overflow:

Operator	Overflow	Operator	Overflow	Operator	Overflow	Operator	Overflow
+	yes	-=	yes	<<	yes	<	no
-	yes	*=	yes	>>	yes	>	no
*	yes	/=	yes	&	no	>=	no
/	yes	%=	no	\|	no	<=	no
%	no	<<=	yes	^	no	==	no
++	yes	>>=	yes	~	no	!=	no
--	yes	&=	no	!	no	&&	no
=	no	\|=	no	un +	no	\|\|	no
+=	yes	^=	no	un -	yes	?:	no

The following sections examine specific operations that are susceptible to integer overflow. The specific tests that are required to guarantee that the operation does not result in an integer overflow depend on the signedness of the integer types. When operating on small types (smaller than int), integer conversion rules apply. The usual arithmetic conversions may also be applied to (implicitly) convert operands to equivalent types before arithmetic operations are performed. Make sure you understand implicit conversion rules before trying to implement secure arithmetic operations.

----