Type-preserving operator new

type-preserving-new.cc

// Test code of http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=6080813.
// Actually, it doesn't require to make type_identifier_to_string.
// The mapping can be obtained from a linker.

#include <map>
#include <string>
#include <typeinfo>

std::map<void *, char *> pointer_to_type_identifier;
std::map<void *, const std::type_info*> pointer_to_type_info;
std::map<char *, std::string> type_identifier_to_string;

template<class T>
class TYPE_IDENTIFIER {
 public:
  static char mDummy;
};

class NoVirtual {
 private:
  int a_value_;
};

class Base {
 public:
  virtual int func() { ; }
 private:
  int a_value_;
};

class Sub : public Base {
 public:
  virtual int func() { ; }
};

template<class T> char TYPE_IDENTIFIER<T>::mDummy = 0;

struct NewTrick {
  template<class T>
  T* operator* (T* pointer) {
    pointer_to_type_identifier[pointer] = &TYPE_IDENTIFIER<T>::mDummy;
    pointer_to_type_info[pointer] = &typeid(T());
    return pointer;
  }
};

#include <iostream>

#define new NewTrick() * new

#define FIND_AND_PRINT_TYPE_IDENTIFIER(p) std::cout << #p << ":" << type_identifier_to_string[pointer_to_type_identifier[((void *)(p))]] << std::endl;
#define FIND_AND_PRINT_TYPE_INFO(p) std::cout << #p << ":" << pointer_to_type_info[((void *)(p))]->name() << std::endl;

int main() {
  type_identifier_to_string[&TYPE_IDENTIFIER<char>::mDummy] = "char";
  type_identifier_to_string[&TYPE_IDENTIFIER<int>::mDummy] = "int";
  type_identifier_to_string[&TYPE_IDENTIFIER<NoVirtual>::mDummy] = "NoVirtual";
  type_identifier_to_string[&TYPE_IDENTIFIER<Base>::mDummy] = "Base";
  type_identifier_to_string[&TYPE_IDENTIFIER<Sub>::mDummy] = "Sub";

  int* x = new int;
  char* y = new char;
  Base* o = new Base;
  NoVirtual* p = new NoVirtual;
  int* z = new int;
  Sub* q = new Sub;

  FIND_AND_PRINT_TYPE_IDENTIFIER(x);
  FIND_AND_PRINT_TYPE_IDENTIFIER(y);
  FIND_AND_PRINT_TYPE_IDENTIFIER(o);
  FIND_AND_PRINT_TYPE_IDENTIFIER(p);
  FIND_AND_PRINT_TYPE_IDENTIFIER(z);
  FIND_AND_PRINT_TYPE_IDENTIFIER(q);
  FIND_AND_PRINT_TYPE_INFO(x);
  FIND_AND_PRINT_TYPE_INFO(y);
  FIND_AND_PRINT_TYPE_INFO(o);
  FIND_AND_PRINT_TYPE_INFO(p);
  FIND_AND_PRINT_TYPE_INFO(z);
  FIND_AND_PRINT_TYPE_INFO(q);

  delete q;
  delete z;
  delete p;
  delete o;
  delete y;
  delete x;
}

typeid() works.

x:int
y:char
o:Base
p:NoVirtual
z:int
q:Sub
x:FivE
y:FcvE
o:F4BasevE
p:F9NoVirtualvE
z:FivE
q:F3SubvE