Automatic Array Repeated Initialization

Automatic Array Repeated Initialization

A simple example of unnecessary double initializations is any type of large local variable, such as an automatic array. When a function makes use of a large array variable with constant data, or even a large constant object, the variable should probably be declared as both “const” and “static”, even if it need not retain its value between calls. Consider the following code example:

    char *convert(int day)
    {
        char *days[] = { "Monday", "Tuesday", "Wednesday",
                    "Thursday", "Friday", "Saturday", "Sunday" };
        return days[day];
    }

The initialization of array “days” illustrates an inefficiency. The initialization of “days” occurs every time the convert function is entered. It would be much more efficient to declare “days” as a static variable to avoid it being re-initialized, and also “const” to help the compiler optimize.

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