Annex C (informative) Compatibility [diff]

C.4 C++ and ISO C++ 2011 [diff.cpp11]

C.4.5 [dcl.dcl]: declarations [diff.cpp11.dcl.dcl]

Affected subclause: [dcl.constexpr]
Change: constexpr non-static member functions are not implicitly const member functions.

Rationale: Necessary to allow constexpr member functions to mutate the object.

Effect on original feature: Valid C++ 2011 code may fail to compile in this revision of C++.
For example, the following code is valid in C++ 2011 but invalid in this revision of C++ because it declares the same member function twice with different return types: struct S { constexpr const int &f(); int &f(); };
Affected subclause: [dcl.init.aggr]
Change: Classes with default member initializers can be aggregates.

Rationale: Necessary to allow default member initializers to be used by aggregate initialization.

Effect on original feature: Valid C++ 2011 code may fail to compile or may change meaning in this revision of C++.
For example: struct S { // Aggregate in C++ 2014 onwards. int m = 1; }; struct X { operator int(); operator S(); }; X a{}; S b{a}; // uses copy constructor in C++ 2011, // performs aggregate initialization in this revision of C++