6.35.3 ARM Type Attributes
class __declspec(notshared) C {
public:
  __declspec(dllimport) C();
  virtual void f();
}
__declspec(dllexport)
C::C() {}
In this code, C::C is exported from the current DLL, but the virtual table for C is not exported. (You can use __attribute__ instead of __declspec if you prefer, but most Symbian OS code uses __declspec.) 
    © Free Software Foundation
Licensed under the GNU Free Documentation License, Version 1.3.
    https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/ARM-Type-Attributes.html