index check in std::array

[Gabriel Dos Reis]

On Tue, Oct 30, 2012 at 1:52 AM, Michael Buro <michael.buro@gmail.com> wrote:
>
> I am wondering why in g++ 4.7.2 (and possibly later versions) indexes
> still are not checked in std::array operator[] when compiling in debug
> mode, which is IMHO the biggest advantage std::array has over
> C-arrays. boost::array has this feature.
>
> The task can be accomplished quite easily - as shown in several forum
> threads. E.g.
>
>       // Element access.
>       reference
>       operator[](size_type __n)
>       {
> // added
> #ifndef NDEBUG
>         if (__n >= _Nm)
>           std::__throw_out_of_range(__N("array::[]"));
> #endif
>         return _M_instance[__n];
>       }
>
>       constexpr const_reference
>       operator[](size_type __n) const noexcept
>       {
> // added
> #ifndef NDEBUG
>         if (__n >= _Nm)
>           std::__throw_out_of_range(__N("array::[]"));
> #endif
>         return _M_instance[__n];
>       }
>
> /MB

Techically, you would get an ODR violation unless
you set NDEBUG consistently in all translation units.

Use at().

-- Gaby