Attributes in C++11/C++14

Specifying Annotations in C++11

C++11 took one big step to minimize the need to use vendor specific syntax. By introducing the standard format, we can move a lot of compiler-specific attributes to the universal set.

C++11 provides a cleaner format of specifying annotations over our code.

The basic syntax is just [[attr]] or [[namespace::attr]].

You can use [[attr]] over almost anything: types, functions, enums, etc., etc.

For example:

[[attrib_name]] void foo() { }      // on a function
struct [[deprecated]] OldStruct { } // on a struct

Attributes in C++11

[[noreturn]]:

It tells the compiler that control flow will not return to the caller. Examples:

• [[noreturn]] void terminate() noexcept;
• functions like std::abort or std::exit are also marked with this attribute.

[[carries_dependency]]:

Indicates that the dependency chain in release-consume std::memory_order propagates in and out of the function, which allows the compiler to skip unnecessary memory fence instructions. Mostly to help to optimise multi-threaded code and when using different memory models.

C++14 Additions

[[deprecated]] and [[deprecated("reason")]]:

Code marked with this attribute wil​l be reported by the compiler. You can set a “reason” why.

Example of [[deprecated]]: