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  1. #include <iostream>
  2. #include <iomanip>
  3. #include <memory>
  4. #include <map>
  5.  
  6. using namespace std;
  7.  
  8. template < typename T >
  9. struct MyAllocator : std::allocator< T > {
  10.  
  11.     // ctors
  12.     MyAllocator() = default;
  13.     MyAllocator( MyAllocator const & ) = default;
  14.     template < typename U >
  15.     MyAllocator( MyAllocator<U> const & ) { }
  16.  
  17.     // member function
  18.     typename std::allocator< T >::pointer
  19.     allocate( typename std::allocator< T >::size_type n,
  20.               std::allocator<void>::const_pointer hint = 0 ) {
  21.  
  22.         typename std::allocator< T >::pointer result = std::allocator< T >::allocate( n, hint );
  23.  
  24.         cout << "allocate(" << n << ", " << hint << ") -> " << result << " "
  25.              << "size = " << sizeof( T ) * n << endl;;
  26.  
  27.         return result;
  28.     }
  29.  
  30.     // member type
  31.     template < typename U >
  32.     struct rebind {
  33.         typedef MyAllocator<U> other;
  34.     };
  35.  
  36. };
  37.  
  38. int main() {
  39.  
  40.     typedef int iIndex;
  41.     typedef std::string Data;
  42.  
  43.     typedef map<
  44.                 iIndex,
  45.                 Data,
  46.                 std::less< iIndex >,
  47.                 MyAllocator< std::pair<const iIndex, Data> >
  48.                > mapData;
  49.  
  50.     typedef int iType;
  51.     typedef map<
  52.                 iType,
  53.                 mapData,
  54.                 std::less< iType >,
  55.                 MyAllocator< std::pair<const iType, mapData> >
  56.                > Foo;
  57.     Foo foo;
  58.  
  59.     foo[ 1 ].insert( make_pair(1, "aaa") );
  60.  
  61. }
  62.  
Success #stdin #stdout 0s 3024KB
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stdin
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Standard input is empty
stdout
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allocate(1, 0) -> 0x93c1020 size = 44
allocate(1, 0) -> 0x93c1050 size = 24
https://ideone.com/yOLvLj
language:
C++14 (gcc 8.3)
created:
13 years ago
visibility:
public

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