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Subject: Re: [std-proposals] New attribute to change the default specifiers and qualifiers
From: Bo Persson (bo_at_[hidden])
Date: 2021-01-19 13:28:02


On 2021-01-19 at 15:35, Vinícius Costa via Std-Proposals wrote:
> Hi!
>
> I'd like to propose a new attribute to change the default specifiers and
> qualifiers in a given scope.
>
> Often there's a lot of boilerplate code involved because the default
> specifiers and qualifiers are not the "correct" ones (stress on the
> quotation marks).
> So we need to explicitly make variables const, functions const, noexcept
> or final, etc.
>
> It would be a lot simpler to have a way to switch the default specifiers
> and qualifiers, making them more permissive or stricter.
>
> The idea is to create an attribute that would apply to a scope. With
> that, we won't mess with back-compatibility and it would allow an easy
> migration towards the new standard.
> Furthermore, it would help to enforce some good practices like
> const-correctness.
>
> For example, the following two codes will be the same.
>
> namespace example [[strict]] {
> class Foo : public Bar
> {
> void do_it(double *ptr) override
> {
> int x = /* some initialization code here*/
> /* more code here */
> }
> };
> }
>
> namespace example {
> class Foo final : public Bar
> {
> void do_it(double * __restrict ptr) const noexcept override final
> {
> const int x = /* some initialization code here*/
> /* more code here */
> }
> };
> }
>

The committee seems to not want attributes to change the meaning of
programs. If a compiler ignores [[noreturn]] or [[nodiscard]] or
[[gnu::special]], the program still works the same (although perhaps
using less optimal code).

Here [[strict]] really affects the meaning!

Also, if I want all the specifiers - except final - how do I do that? :-)

     Bo Persson


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