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Does Visual Studio 2017 fully support N4266 with the [[deprecated]] attribute?

I am currently exploring new features in C ++ 17. I came across a function N4266 , which says that now enums and namespaces can also use attributes. Various sources say that Visual Studio 2017 already fully supports this feature. I wrote a test with the attribute [[deprecated]]. For namespaces, this works very well. However, no warnings are generated for listings. Is there a mistake in my implementation? Did I miss something?

enum MyEnum { val = 0, vaal[[deprecated]] = val }; void test() { MyEnum e = MyEnum::vaal; //Should emit Warning, but does not MyEnum e2 = MyEnum::val; //No Warning }

I am using Visual Studio Community 2017 Version 15.3.5. It says that it should be supported with VS2015 already. / std: C ++ 17.

And it also says that it must be the correct syntax.

It makes no difference if I use the enum or enum class.

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No, not at all.

I would say that this is the current limitation / error in MSVC2017, which may deserve to be recorded as an error report even if the attribute is also recognized in the case of an enumerator (and does not request warning C5030, as Mark pointed out in the comments to you question).

Application: which has now been verified (as a previously known bug) by the link provided by Hans Passant:

The C ++ 17 standard (working draft), [decl.attr.deprecated] , indicates:

§1 The deprecated token attribute can be used to mark names and entities whose use is still permitted, but the reason is not recommended.

§3 An attribute can be applied to a class declaration, and typedef-name, variable, non-static data member, function, namespace, enumeration, enumeration or pattern specialization ....

Using the /std:c++17 flag when compiling with MSVC2017, the deprecated attribute works for all of the above, but lists:

 // a class class [[deprecated]] MyClass {}; // a typedef-name / type alias [[deprecated]] typedef int MyInt; using MyFloat [[deprecated]] = float; // a variable (see main) // a non-static data member struct DataMember { int b [[deprecated]]; }; // a function [[deprecated]] void myFunction() {} // a namespace namespace [[deprecated]] my_namespace { typedef double MyDouble; } // an enumeration enum [[deprecated]] MyEnum {}; // an enumeration enum MyNewEnum { val[[deprecated]] = 42 }; // a template specialization template <typename T> void myTemplateFunction(const T) {} template<> [[deprecated]] void myTemplateFunction<int>(const int) {} int main() { MyClass m; // warning C4996: 'MyClass': was declared deprecated MyInt i; // warning C4996: 'MyInt': was declared deprecated MyFloat f; // warning C4996: 'MyInt': was declared deprecated int j [[deprecated]]; j = 1; // warning C4996: 'j': was declared deprecated DataMember dm; dm.b = 1; // warning C4996: 'DataMember::b': was declared deprecated myFunction(); // warning C4996: 'myFunction': was declared deprecated my_namespace::MyDouble d; // warning C4996: 'my_namespace': was declared deprecated MyEnum e; // warning C4996: 'MyEnum': was declared deprecated myTemplateFunction(2); // warning C4996: 'myTemplateFunction': was declared deprecated MyNewEnum ne = val; // ... no warning return 0; }

Both gcc and clang cause failure warnings for MyNewEnum ne = val; above for -std=c++14 as well as -std=c++1z .

In a related note, especially the cppreference description of the deprecated attribute does not seem to have been updated with N4266, apart from the "enumerator" and "namespace" in valid usage declarations; although they are both present in the standard version of C ++ 14 (7.6.5 / 2) . This may be an indicator that this is a rarely used function (applied to counters / namespaces), which may explain why it was (partially) skipped in MVCS.

  • Edit: A note about this has been added, and it has since been fixed.

Some ambiguity in the official MVSC documentation

Finally, the section in the MSVC docs does not actually contain details about what types of declarations the deprecated attribute is allowed on; showing only an example of rejecting a function declaration.

Although, as you pointed out (however, by reference to cppreference, and not in your own MSVC docs), MSVS2015 clearly indicates N4266 compliance , at least for C ++ 17.

Compiler functions

C ++ 17 Basic functions of the language

N4266 Attributes for namespaces and counters

Supported: VS2015

However, Support for C ++ 11/14/17 Features (Modern C ++) points to the opposite (for VS2015):

Compiler functions

C ++ 17 Suggested basic language features

N4266 Attributes for namespaces and counters

Supported VS2013: No

Supported VS2015: No

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Source: https://habr.com/ru/post/1272527/

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