This is the problem: cc-mode relies somewhat on the assumption that keywords are single words. Adding support for enum_class instead of enum class would just be a matter of changing a few regexps. Instead Emacs treats this as a class. The correct way of solving this would be teaching Emacs that this is an enum. … Read more
The official name is not universal reference, but forwarding reference. The Standard states that only rvalue references to cv-unqualified template parameters fall in this category: 14.8.2.1 Deducing template arguments from a function call [temp.deduct.call] 3 If P is a cv-qualified type, the top level cv-qualifiers of P’s type are ignored for type deduction. If P … Read more
You can’t declare nested types outside the class definition. If you need to use them outside the class, you will have to either include the class definition, or move them into a namespace.
This is definitely a compiler bug, and actually one that has been known for quite some time: GCC #47346 (first reported in Jan 2011) and Clang #15914 (first reported May 2013). Your __tklass is clearly private, and the template alias is not marked friend, so this should be a simple access error. The simplest reproduction … Read more
In c++17, with the addition of auto in template arguments (P0127), I think you can now do: template<auto value> struct MyStruct {}; template<typename Class, typename Result, Result Class::* value> struct MyStruct<value> { // add members using Class, Result, and value here using containing_type = Class; }; typename MyStruct<&Something::theotherthing>::containing_type x = Something();
The rule for this situation changed between 2011 and 2014. The compiler should now treat localB as an rvalue. The applicable rule for return statements is found in §12.8 [class.copy]/p32, which reads in C++14 (quoting N3936, emphasis mine): When the criteria for elision of a copy/move operation are met, but not for an exception-declaration, and … Read more
Somewhere under the covers, unique_ptr<foo> has a data member of type foo*. However, it’s not legitimate for a user of the class to directly modify that data member. Doing so would not necessarily preserve the class invariants of unique_ptr, in particular it wouldn’t free the old pointer value (if any). In your special case you … Read more
Since the implicit constructor is actually constexpr in your case… [C++11: 12.1/6]: [..] If that user-written default constructor would satisfy the requirements of a constexpr constructor (7.1.5), the implicitly-defined default constructor is constexpr. [..] [C++11: 7.1.5/3]: The definition of a constexpr function shall satisfy the following constraints: it shall not be virtual (10.3); its return … Read more
In C++98/03 there was good reason to not have a non-const data() due to the fact that string was often implemented as COW. A non-const data() would have required a copy to be made if the refcount was greater than 1. While possible, this was not seen as desirable in C++98/03. In Oct. 2005 the … Read more
Andrei Alexandrescu, C++ programmer extraordinaire who wrote “Modern C++ Design” once wrote a great article about building different string implementations with customizable storage systems. His article (linked here) describes how you can do what you’ve described above as a special case of a much more general system that can handle all sorts of clever memory … Read more