namespace bug, ICE.

[Peter Nordlund <peter dot nordlund at lentus dot se>]

This code produces an ICE on gcc 2000-06-04.
The code doesnt work on KCC 3.4 either, but with quite a different
behaviour.
See compilation commands and output att the bottom of the code.

Best regards,
Peter
//------------

#ifndef NSBUG
#  define NAMESPACE_BUG //GCC gets an ICE if explicit scoping is used.
#else
#  define NAMESPACE_BUG ManagedSingleton::
#endif

namespace ManagedSingleton {

template <typename T /* Singleton type */, typename MANAGER>
class Singleton {
public:
  typedef MANAGER ManagerType;
  typedef T       SingletonType;
  inline static T& instance();            //>x
  inline static const T& constInstance(); //>x
protected:
  Singleton()  { };                       // NOTHROW
  ~Singleton() { };                       // NOTHROW
};

// Master template, should never be used.
template <typename T, typename MANAGER> class InstanceManager{};

/////////////////////////////////////////////////////////
// Implementations
//
template <typename T, typename MANAGER>
inline T& Singleton<T, MANAGER>::instance() {
  T* typeArg = 0;
  return MANAGER::instance(typeArg); //>x
}

template <typename T, typename MANAGER>
inline const T& Singleton<T, MANAGER>::constInstance() { return
instance(); }

}; // namespace ManagedSingleton

//##########################

namespace ManagedSingleton {

  // Simple Singleton Manager with no cleanup.
  // (Has bad performance under Cygwin and gcc 2.95.2.)
  //
  struct NoCleanupMgr2 {
    template <typename T> static T& instance(T*) {         //>x
      return InstanceManager<T, NoCleanupMgr2>::instance();//>x
    }
  };

  // Template specialization.
  template <typename T>
  class InstanceManager<T, NoCleanupMgr2> {
    friend class NoCleanupMgr2;
    static T& instance() {          //>x
      static T* instance_ = new T;  //>x
      return *instance_;            // NOTHROW
    }
  };

}; // namespace ManagedSingleton

//##################################################

using namespace ManagedSingleton;

// Test class
template <int I, typename MGR>
class Test: public Singleton<Test<I, MGR>, MGR> {
  template <typename DS, typename MGR2> friend class NAMESPACE_BUG
InstanceManager;
private:
  Test() {};
};

typedef Test<1, NoCleanupMgr2> Test1;

int main(int argc, const char** argv){
  Test1::constInstance();
  return 0;
}
//##############################################
#if 0
This code produces an ICE on gcc.
The code doesnt work on KCC either, but with quite a different
behaviour.
See compilation commands and output below:
>>uname -a
Linux peternl 2.2.12-20 #1 Wed May 24 16:03:15 CEST 2000 i686 unknown
>>g++ -v
Reading specs from
/home/petern/gcc/install/gcc/2000-06-04/lib/gcc-lib/i686-pc-linux-gnu/2.96/specs

gcc version 2.96 20000604 (experimental)

// ## Gcc 2000-06-04
>>g++ bug.cpp // ###### Works ok!
>>g++ -DNSBUG bug.cpp
bug.cpp: In instantiation of Test<1, ManagedSingleton::NoCleanupMgr2>:
bug.cpp:79:   instantiated from here
bug.cpp:70: Internal compiler error.
bug.cpp:70: Please submit a full bug report.
bug.cpp:70: See <URL:http://www.gnu.org/software/gcc/bugs.html> for
instructions.


// ## KCC 3.4
>>KCC -DNSBUG bug.cpp // ###### Works ok!
>>KCC bug.cpp
"bug.cpp", line 57: error: "Test<I, MGR>::Test() [with I=1,
          MGR=ManagedSingleton::NoCleanupMgr2]" is inaccessible
        static T* instance_ = new T;  //>x
                                  ^
          detected during:
            instantiation of "T &ManagedSingleton::InstanceManager<T,
                      ManagedSingleton::NoCleanupMgr2>::instance() [with

                      T=Test<1, ManagedSingleton::NoCleanupMgr2>]" at
line 48
            instantiation of "T
&ManagedSingleton::NoCleanupMgr2::instance(T
                      *) [with T=Test<1,
ManagedSingleton::NoCleanupMgr2>]" at
                      line 31
            instantiation of "T &ManagedSingleton::Singleton<T,
                      MANAGER>::instance() [with T=Test<1,
                      ManagedSingleton::NoCleanupMgr2>,
                      MANAGER=ManagedSingleton::NoCleanupMgr2]" at line
35
            instantiation of "const T &ManagedSingleton::Singleton<T,
                      MANAGER>::constInstance() [with T=Test<1,
                      ManagedSingleton::NoCleanupMgr2>,
                      MANAGER=ManagedSingleton::NoCleanupMgr2]" at line
79

1 error detected in the compilation of "bug.cpp".
KCC: Compilation failed.

#endif // #if 0