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INT31-EX1: C99 defines minimum ranges for standard integer types. For example, the minimum range for an object of type unsigned short int is 0 to 65,535, while the minimum range for int is -32,767 to +32,767. This means that it is not always possible to represent all possible values of an unsigned short int as an int. However, on the IA-32 architecture, for example, the actual integer range is from -2,147,483,648 to +2,147,483,647, meaning that it is quite possible to represent all the values of an unsigned short int as an int for this architecture. As a result, it is not necessary to provide a test for this conversion on IA-32. It is not possible to make assumptions about conversions without knowing the precision of the underlying types. If these tests are not provided, assumptions concerning precision must be clearly documented, as the resulting code cannot be safely ported to a system where these assumptions are invalid. A good way to document these assumptions is by using static assertions (see DCL03-AC. Use a static assertion to test the value of a constant expression).
Risk Assessment
Integer truncation errors can lead to buffer overflows and the execution of arbitrary code by an attacker.
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