Don't insist that all declarations should be at the top of a function

Reason

The "all declarations on top" rule is a legacy of old programming languages that didn't allow initialization of variables and constants after a statement. This leads to longer programs and more errors caused by uninitialized and wrongly initialized variables.

Example, bad

int use(int x)
{
    int i;
    char c;
    double d;

    // ... some stuff ...

    if (x < i) {
        // ...
        i = f(x, d);
    }
    if (i < x) {
        // ...
        i = g(x, c);
    }
    return i;
}

The larger the distance between the uninitialized variable and its use, the larger the chance of a bug. Fortunately, compilers catch many "used before set" errors. Unfortunately, compilers cannot catch all such errors and unfortunately, the bugs aren't always as simple to spot as in this small example.

Alternative

• Always initialize an object
• ES.21: Don't introduce a variable (or constant) before you need to use it