User-defined attributes in C++11?

Question

Is there a way to create user-defined attributes in C++11 or later?

For example,

[[noreturn]] void exit();

is a compiler-defined C++11 attribute.

I'd like to define something like:

[[comingsoon]] int function(int);

Is there a mechanism for this?

Edit: I should mention I'm using Clang.

Check [here](http://stackoverflow.com/questions/9864328/using-c11-attributes). _Attributes (a new C++11 feature) are just a standardized syntax for compiler extensions. Because they're intended for compiler extensions, there's no standard way of creating your own attributes, like you can with Java annotations or C# attributes._ — Michael, Jan 15 '16 at 19:12
It looks like [you can in MSVS](https://msdn.microsoft.com/en-us/library/yd21828z.aspx) but it is a compiler extension. — NathanOliver, Jan 15 '16 at 19:12

score 11 · Answer 1 · answered Apr 29 '17 at 14:12

For now it's not possible to define user-attributes.

There is, as far as i know, no information about if this feature is planned or not. However, look at this FAQ answer from Stroustrup : https://isocpp.org/wiki/faq/cpp11-language-misc#attributes, especially this part :

One planned use for attributes is improved support for OpenMP. For example:

for [ [ omp::parallel() ] ] (int i=0; i<v.size(); ++i) {
    // ...
}

It could mean that they plan to allow programmer to define it's own attribute. Wait & see.

score 7 · Accepted Answer · answered Jan 15 '16 at 20:19

7

The language provides no way of adding attributes.

Of course, if you are using Clang, you can edit the source of Clang, and add any attributes you like.

answered Jan 15 '16 at 20:19

1

Do you know if there are plans for future versions of C++ to allow users to add attributes? – oconnor0 Jan 15 '16 at 20:51
1

I don't know. I would guess not. C++ doesn't have the sort of reflection capabilities that would make it useful. – Martin Bonner supports Monica Jan 15 '16 at 21:03
Not sure this answer remains true. https://msdn.microsoft.com/en-us/library/60e6k732.aspx – S Meaden Aug 01 '16 at 20:26
2

I think that is talking about C++/CLI which is MS's extension to C++. There is very little chance of that working it's way back into the standard language. – Martin Bonner supports Monica Aug 02 '16 at 05:26
whats the point of implementing attributes if users cannot define custom ones ? seems like unnecessary bloat – Dec 21 '20 at 14:18
@orenrevenge - it allows *compiler writers* to add their own. – Martin Bonner supports Monica Dec 21 '20 at 15:44

2 Answers2