# V669. Argument is a non-constant reference. The analyzer is unable to determine the position where this argument is modified. Consider checking the function for an error.

The analyzer has detected that an argument is being passed by reference into a function but not modified inside the function body. This may indicate an error which is caused by a misprint.

Consider a sample of incorrect code:

    void foo(int &a, int &b, int c)
    {
      a = b == c;
    }

Because of a misprint, the assignment operator ('=') has turned into the comparison operator ('=='). As a result, the 'b' variable is used only for reading, although this is a non-constant reference. The way of fixing the code is chosen individually in each particular case. The important thing is that such a code requires more thorough investigation.

This is the fixed code:

    void foo(int &a, int &b, int c)
    {
      a = b = c;
    }

Note. The analyzer might make mistakes when trying to figure out whether or not a variable is modified inside the function body. If you get an obvious false positive, please send us the corresponding code fragment for us to study it.

You may also add the comment "//-V669" to suppress the false positive in a particular line.

You can look at examples of errors detected by the V669 diagnostic.