Should _GLIBCXX_DEBUG affect tr1/array?

[Jonathan Wakely]

On 17 January 2012 11:17, Edward Rosten wrote:
>
> How interesting! I didn't realist that. In that case, is the following OK?
>
> It seems to fit the bill about being both constexpr and bound checking
> with the libstdc++ standard error messages:
>
> #define _GLIBCXX_DEBUG
> #include <debug/debug.h>
>
>
> template<int Size> struct Die
> {
>        int size() const
>        {
>                return Size;
>        }
>
>        Die(int n)
>        {
>                __glibcxx_check_subscript(n);
>        }
> };
>
> template<int Size, class C> struct Array
> {
>        constexpr int operator[](int n) noexcept
>        {
>                return n>=Size?throw Die<Size>(n):0;
>        }

I'm surprised that you can throw a non-literal type (i.e. one without
a constexpr constructor) from a constexpr function, but apparently
it's OK.

> };
>
> int main()
> {
>        Array<10, int> a;
>
>        a[11];
> }
> I think the main refinement would be not to be some conditional
> compilation so that throw is never used in non-debug mode to allow for
> better optimization.

Yes, and so the comparison isn't done except in debug mode.