Multiplication result converted to larger type #363
Description
This rule finds code that converts the result of an integer multiplication to a larger type. Since the conversion applies after the multiplication, arithmetic overflow may still occur. The rule flags every multiplication of two non-constant integer expressions that is (explicitly or implicitly) converted to a larger integer type. The conversion is an indication that the expression would produce a result that would be too large to fit in the smaller integer type.
POC
int i = 2000000000;
long j = i * i; //Wrong: due to overflow on the multiplication between ints,
//will result to j being -1651507200, not 4000000000000000000
long k = (long) i * i; //Correct: the multiplication is done on longs instead of ints,
//and will not overflow
long l = static_cast<long>(i) * i; //Correct: modern C++