Bug 21243

This problem may be related to Bug report 17470.
The typeinfo of a template class instantiation can not be changed with
 __attribute__ ((visibility("default"))).
Example:

template<typename T> class Abc{
public:
  virtual ~Abc(){}
};
template class __attribute__ ((visibility("default"))) Abc<int>;
Abc<int> tmp;

pesch@kstbu027[~/src/c++/test]1238: g++ -fPIC -fvisibility=hidden
-fvisibility-inlines-hidden -c visibility.cpp
pesch@kstbu027[~/src/c++/test]1239: g++ -shared visibility.o -o libvisibility.so
pesch@kstbu027[~/src/c++/test]1240: nm -C libvisibility.so | grep Abc
00000764 t Abc<int>::Abc()
0000072a t Abc<int>::~Abc()
000006f0 t Abc<int>::~Abc()
000006b6 t Abc<int>::~Abc()
00001930 d typeinfo for Abc<int>
000007ee r typeinfo name for Abc<int>
00001938 d vtable for Abc<int>


Using pragma works:

template<typename T> class Abc{
public:
  virtual ~Abc(){}
};
#pragma GCC visibility push(default)
template class Abc<int>;
#pragma GCC visibility pop
Abc<int> tmp;

pesch@kstbu027[~/src/c++/test]1241: g++ -fPIC -fvisibility=hidden
-fvisibility-inlines-hidden -c visibility.cpp
pesch@kstbu027[~/src/c++/test]1242: g++ -shared visibility.o -o libvisibility.so
pesch@kstbu027[~/src/c++/test]1243: nm -C libvisibility.so | grep Abc
000007c4 t Abc<int>::Abc()
0000078a t Abc<int>::~Abc()
00000750 t Abc<int>::~Abc()
00000716 t Abc<int>::~Abc()
00001990 V typeinfo for Abc<int>
0000084e V typeinfo name for Abc<int>
00001998 V vtable for Abc<int>


Because #pragma can not be used in a macro I would prefer to
use the __attribute__ syntax.