# V302\. Member operator\[\] of 'foo' class has a 32\-bit type argument\. Use memsize\-type here\.


> This rule belongs to the "Diagnosis of 64\\\-bit errors" group\\\. The rules in this group are no longer developed and may be disabled in the future\\\. If you use these rules, please \[contact our support team\]\(https://pvs\-studio\.com/en/about\-feedback/\)—we will help you find a replacement or suggest an alternative solution\\\.

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: 

```cpp
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:

```cpp
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:

```cpp
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;
```

The related diagnostic warnings are [V108](https://pvs-studio.com/en/docs/warnings/v108/) and [V120](https://pvs-studio.com/en/docs/warnings/v120/)\.