Bounds checked array that shorts out static access

Question

C++. Imagine I'm putting together a class for statically sized, bounds checked array:

template<typename T, int N>
class MyArray
{
    T a[N];
public:
    T & operator[](int i)
    {
         if(i < 0 || i >= N)
             OnError(); //Crash and die horribly
         return a[i];
    }
};

Is there a way to avoid performing a bound check at run time if the array access operator is invoked with a compile time constant as an argument?

"I'm putting together a class for statically sized, bounds checked array" - so, you are intentionally reproducing what std::array and its at() method already do? — Remy Lebeau
– Remy Lebeau, Commented Mar 4, 2021 at 2:32
@Remy: long story there. std::array as it is won't do. The question says "imagine". — Seva Alekseyev
– Seva Alekseyev, Commented Mar 4, 2021 at 14:39

eerorika · Accepted Answer · 2021-03-04 03:00:48Z

1

Is there a way to avoid performing a bound check at run time if the array access operator is invoked with a compile time constant as an argument?

You don't necessarily need to do anything yourself other than enable the optimiser. Compilers are smart, can expand function calls inline and can fold branches that are known at compile time.

answered Mar 4, 2021 at 3:00

eerorika

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