==== reinterpret_cast ====

=== What is the proper way to initialize a pointer member in C++ (11)? ===
	

Any hint to do proper const static member pointer initialization using C++ 11 and later ?

Source:

struct App {
  static const App* ok;
  static constexpr App* ko = reinterpret_cast<App*>(0xBADC0DE); // <= FTBFS
};
const App* App::ok = reinterpret_cast<App*>(0xBADC0DE);

Try it on latest gcc or clang it will fail :

    http://melpon.org/wandbox/permlink/IlXTqNiVoJtnFDg0
    http://cpp.sh/96mau
    http://coliru.stacked-crooked.com/a/e031835a72ed2172

The reason of fail is clear : reinterpret_cast and constexpr are exclusives according to C++11 standard (but was accepted in some compiler).

    http://eel.is/c++draft/expr.const#2
    http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3797.pdf (p125)

But older 2 steps method still works but not single one (on gcc-6.2.0 at least).

This code looks a bit odd, I agree on that but how to get it working or clang or latest g++.

Declaration and init in 2 places can be a workaround but it does not fully explain (init to nullptr is working of course).

Related errors are :

  error: 'constexpr' needed for in-class initialization of static data member
  error: reinterpret_cast from integer to pointer

More resources:

    reinterpret_cast<> and portabilty


   * http://stackoverflow.com/questions/39441338/what-is-the-proper-way-to-initialize-a-pointer-member-in-c-11
   * http://stackoverflow.com/questions/23401489/reinterpret-cast-and-portabilty#

</code>
==== C cast ====

  /// @author: http://rzr.online.fr/contact.htm
  #include <cstdlib>
  // #define FIX // uncomment
  /// show why anonymous types are evil in C++
  struct foo {
  #ifndef FIX
    struct  {} *m; // anonymous type make cast impossible in C++ (ok on C)
  #else
    struct foo_m {} *m; // this way the type is named and can be used
  #endif
  };
  int main(int /* argc*/ , char* /* argv*/ [])
  {
    struct foo o; o.m = 0;
  #ifndef FIX
    o.m = malloc(sizeof( o.m ));  //error:
    //  invalid conversion from 'void*' to 'foo::<anonymous struct>*'
  #else
    o.m =
      (struct foo::foo_m*)  //mandatory in c++
      malloc(sizeof( o.m ));
  #endif
    return 0;
  }
  //#eof "$Id: rzr --  --  $"

  * http://bugs.debian.org/447196
  * http://sourceforge.net/tracker/index.php?func=detail&aid=1816107&group_id=12349&atid=312349


==== reinterpret_cast ====


  error: reinterpret_cast from integer to pointer

  * http://stackoverflow.com/questions/39441338/what-is-the-proper-way-to-intialize-a-pointer-member-in-c-11
  * http://stackoverflow.com/questions/10369606/constexpr-pointer-value# ConstExpr
  * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63715# ConsT
  * http://stackoverflow.com/questions/27946241/workaround-for-gcc-4-9-constexpr-bug
  * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63715# CasT
  * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70172# ExpressioN
  * http://stackoverflow.com/questions/32790106/passing-reference-pointing-to-struct-as-template-parameter
  * http://stackoverflow.com/questions/13499658/constexpr-initializing-with-pointers# StatiC
  * http://stackoverflow.com/questions/23401489/reinterpret-cast-and-portabilty# ReinterpretCast


   error: 'constexpr' needed for in-class initialization of static data member 


@TaG: [[CPlusPlus]] [[gcc]]