Summary of Compile-Time Breaking Changes
This topic summarizes the compile-time errors and warnings that will now be issued on code that compiled without errors or warnings prior to Visual C++ 2003. However, some conformance-related, compile-time breaking changes were introduced in Visual C++ 2005.
Closing parentheses now required for the defined preprocessor directive (C2004).
Missing typename keyword and explicit specializations no longer find template parameters from primary template (C2146 ).
A protected member (n) can only be accessed through a member function of a class (B) that inherits from the class (A) of which it (n) is a member (C2247).
Improved accessibility checks in compiler now detect inaccessible base classes (C2247).
An explicit specialization can not be a copy constructor or copy assignment operator (C2299).
An exception cannot be caught if the destructor and/or copy constructor is inaccessible (C2316).
Default arguments on pointers to functions no longer allowed (C2383).
A static data member cannot be initialized via derived class (C2477).
The initialization of a typedef is not allowed by the standard and now generates a compiler error (C2513).
bool is now a proper type (C2632).
A UDC can now create ambiguity with overloaded operators (C2666).
A qualification conversion is not the same as identity conversion (C2666).
More expressions are now considered valid null pointer constants (C2668).
template<>is now required in places where the compiler would previously infer it (C2768).The explicit specialization of a member function outside the class is not valid if the function has already been explicitly specialized via a template class specialization. (C2910).
For every explicit specialization, you must chose the parameters of the every explicit specialization, such that, they match the parameters of the primary template (C2912).
Floating point non-type template parameters are no longer allowed (C2993).
Class templates are not allowed as template type arguments (C3206).
Friend function names are no longer introduced into containing namespace (C3767).
Enhanced pointer-to-member conformance (C3867).
The compiler will no longer accept extra commas in a macro (C4002).
An object of POD type constructed with an initializer of the form () will be default-initialized (C4345).
typenameis now required if a dependent name is to be treated as a type (C4346).Functions that were incorrectly considered template specializations are no longer considered so (C4347).
Static data members cannot be initialized via derived class (C4356).
A class template specialization needs to be defined before it was used in a return type (C4686).
The compiler now reports unreachable code (C4702).
A friend declaration that declares a new non-template function must be defined (LNK2019).