(malloc/freeを用いた) デバッグ用 allocator

#include <cstdio>
#include <cstdlib>
#include <new>
#include <typeinfo>

namespace epi {

  template<typename T> struct mallocator {
    typedef T value_type;
    template<typename U> mallocator(const mallocator<U>&) {}

    mallocator() {}
    bool operator==(const mallocator&) const{ return true;  }
    bool operator!=(const mallocator&) const{ return false; }

    T* allocate(const size_t n) const {
      if ( n == 0 ) 
        return nullptr;
      if (n > static_cast<size_t>(-1) / sizeof(T) )
        throw std::bad_array_new_length();
      void* pv = std::malloc(n * sizeof(T));
      if ( !pv )
        throw std::bad_alloc();
      printf("%d %s MALLOC : %p\n", n, typeid(T).name(), pv);
      return static_cast<T*>(pv);
    }

    void deallocate(T* const p, size_t n) const {
        printf("%d %s FREE :   %p\n", n, typeid(T).name(), p);
        std::free(p);
    }

    void construct(T* p, const T& val) { new ((void*)p) T(val); }

    void destroy(T* p) { p->T::~T(); }

    template<typename Other> struct rebind {
        typedef mallocator<Other> other;
    };
  };

}

/*
 * おためし
 */
#include <vector>
#include <string>
#include <iostream>

// epi::mallocator を使った vector と string (alias templates)
template<typename T> using my_vec = std::vector<T, epi::mallocator<T>>;
template<typename T> using my_str = std::basic_string<T, std::char_traits<T>, epi::mallocator<T>>;

using namespace std;

int main() {
  my_vec<int> vi;
  my_vec<my_str<char>> vs;
  vi.emplace_back(1); vi.emplace_back(2); vi.emplace_back(3);
  vs.emplace_back("one"); vs.emplace_back("two"); vs.emplace_back("three");
  for (int n : vi) { cout << n << ' '; } cout << endl;
  for (my_str<char> s : vs) { cout << s << ' '; } cout << endl;
}

/* 実行結果: (Visaul C++ 2013)
1 int MALLOC : 00B3B1D0
2 int MALLOC : 00B3B0E0
1 int FREE : 00B3B1D0
3 int MALLOC : 00B37B18
2 int FREE : 00B3B0E0
1 class std::basic_string<char, struct std::char_traits<char>, struct epi::mallocator<char> > MALLOC : 00B34F58
2 class std::basic_string<char, struct std::char_traits<char>, struct epi::mallocator<char> > MALLOC : 00B37810
1 class std::basic_string<char, struct std::char_traits<char>, struct epi::mallocator<char> > FREE : 00B34F58
3 class std::basic_string<char, struct std::char_traits<char>, struct epi::mallocator<char> > MALLOC : 00B3AF18
2 class std::basic_string<char, struct std::char_traits<char>, struct epi::mallocator<char> > FREE : 00B37810
1 2 3
one two three
3 class std::basic_string<char, struct std::char_traits<char>, struct epi::mallocator<char> > FREE : 00B3AF18
3 int FREE : 00B37B18
*/