# V778. Two similar code fragments. Perhaps, it is a typo and 'X' variable should be used instead of 'Y'.

The analyzer detected a possible typo in a code fragment that was very likely written by using the Copy-Paste technique.

The V778 diagnostic looks for two adjacent code blocks with similar structure and different variable names. It is designed to detect situations where a code block is copied to make another block and the programmer forgets to change the names of some of the variables in the resulting block.

Consider the following example:

    void Example(int a, int b)
    {
      ....
      if (a > 50)
        doSomething(a);
      else if (a > 40)
        doSomething2(a);
      else
        doSomething3(a);

      if (b > 50)
        doSomething(b);
      else if (a > 40)    // <=
        doSomething2(b);
      else
        doSomething3(b);
      ....
    }

This code was written by using Copy-Paste. The programmer skipped one of the instances of the 'a' variable that was to be replaced with 'b'. The fixed code should look like this:

    void Example(int a, int b)
    {
      ....
      if (a > 50)
        doSomething(a);
      else if (a > 40)
        doSomething2(a);
      else
        doSomething3(a);

      if (b > 50)
        doSomething(b);
      else if (b > 40)
        doSomething2(b);
      else
        doSomething3(b);
      ....
    }

The following example is taken from a real project:

    ....
    if(erendlinen>239) erendlinen=239;
    if(srendlinen>erendlinen) srendlinen=erendlinen;

    if(erendlinep>239) erendlinep=239;
    if(srendlinep>erendlinen) srendlinep=erendlinep;   // <=
    ....

Unlike the previous example, the problem in this one is not clearly visible. The variables have similar names, which makes it much more difficult to diagnose the error. In the second block, variable 'erendlinep' should be used instead of 'erendlinen'.

Obviously, 'erendlinen' and 'erendlinep' are poorly chosen variable names. An error like that is almost impossible to catch during code review. Well, even with the analyzer pointing at it directly, it is still not easy to notice. Therefore, take your time and make sure to examine the code closely when getting a V778 warning.

This diagnostic is classified as:

CWE-682

You can look at examples of errors detected by the V778 diagnostic.