# V695. Range intersections are possible within conditional expressions.

The analyzer has detected a potential error in a condition. The program must perform different actions depending on which range of values a certain variable meets.

For this purpose, the following construct is used in the code:

    if ( MIN_A < X && X < MAX_A ) {
      ....
    } else if ( MIN_B < X && X < MAX_B ) {
      ....
    }

The analyzer generates the warning when the ranges checked in conditions overlap. For example:

    if ( 0 <= X && X < 10)
      FooA();
    else if ( 10 <= X && X < 20)
      FooB();
    else if ( 20 <= X && X < 300)
      FooC();
    else if ( 30 <= X && X < 40)
      FooD();

The code contains a typo. The programmer's fingers faltered at some moment and he wrote "20 <= X && X < 300" instead of "20 <= X && X < 30" by mistake. If the X variable stores, for example, the value 35, it will be the function FooC() that will be called instead of FooD().

The fixed code:

    if ( 0 <= X && X < 10)
      FooA();
    else if ( 10 <= X && X < 20)
      FooB();
    else if ( 20 <= X && X < 30)
      FooC();
    else if ( 30 <= X && X < 40)
      FooD();

Here is another example:

    const int nv_ab = 5;
    const int nv_bc = 10;
    const int nv_re = 15;
    const int nv_we = 20;
    const int nv_tw = 25;
    const int nv_ww = 30;
    ....
    if (n < nv_ab) { AB(); }
    else if (n < nv_bc) { BC(); }
    else if (n < nv_re) { RE(); }
    else if (n < nv_tw) { TW(); }   // <=
    else if (n < nv_we) { WE(); }   // <=
    else if (n < nv_ww) { WW(); }

Depending on the value of the 'n' variable, different actions are performed. Poor variable naming may confuse a programmer - and so it did in this example. The 'n' variable should have been compared to 'nv_we' first and only then to 'nv_tw'.

To make the mistake clear, let's substitute the values of the constants into the code:

    if (n < 5) { AB(); }
    else if (n < 10) { BC(); }
    else if (n < 15) { RE(); }
    else if (n < 25) { TW(); }
    else if (n < 20) { WE(); } // Condition is always false
    else if (n < 30) { WW(); }

The fixed code:

    if (n < nv_ab) { AB(); }
    else if (n < nv_bc) { BC(); }
    else if (n < nv_re) { RE(); }
    else if (n < nv_we) { WE(); }    // <=
    else if (n < nv_tw) { TW(); }    // <=
    else if (n < nv_ww) { WW(); }

This diagnostic is classified as:

CWE-561 CWE-670 CERT-MSC01-C

You can look at examples of errors detected by the V695 diagnostic.