The analyzer detected a potential error of working with classes that contain operator[]. Classes with an overloaded operator[] are usually a kind of an array where the index of the item being called is operator[] argument. If operator[] has a 32-bit type argument it might indicate an error.
Let us consider an example leading to the warning V302:
class MyArray {
std::vector<float> m_arr;
...
float &operator[](int i) //V302
{
DoSomething();
return m_arr[i];
}
} A;
...
int x = 2000;
int y = 2000;
int z = 2000;
A[x * y * z] = 33;If the class is designed to work with many arguments, implementing operator[] like this is incorrect because it does not allow addressing the items whose numbers are more than UINT_MAX. To diagnose the error in the example above you should point to the potentially incorrect operator[]. The expression "x * y * z" does not look suspicious because there is no implicit type conversion. When we correct operator[] in the following way:
float &operator[](ptrdiff_t i);PVS-Studio analyzer warns about a potential error in the line "A[x * y * z] = 33;" and now we can make the code absolutely correct. Here is an example of the corrected code:
class MyArray {
std::vector<float> m_arr;
...
float &operator[](ptrdiff_t i) //V302
{
DoSomething();
return m_arr[i];
}
} A;
...
ptrdiff_t x = 2000;
ptrdiff_t y = 2000;
ptrdiff_t z = 2000;
A[x * y * z] = 33;