Type Casting

[gothic_coder]

Hello All, I am always confused between static, dynamic, and reinterpret casting. I tried to find answers but somehow they all are confusing... Could anyone clears this concept. Thanks.

[Cedric Moonen]

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Cédric Moonen Software developer
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[gothic_coder]

Cool, Thanks... I'm checking :)

[Sauro Viti]

static_cast and reinterpret_cast work in the same way than the classic C-style cast, but they are used in two different context:

• static_cast is used when casting between two related types, for instance from a numeric type to another. The conversion could generate a loss of data, but without the cast operator the code compile; the compiler could generate a warning.

  char a, b;
  int x = 123;
  double y = 123.456;
  a = static_cast<char>(x); // From int to char
  b = static_cast<char>(y); // From double to char

• reinpterpret_cast is used when casting between two unrelated types, usually pointers, for instance from a pointer to a struct to a pointer to char. Without the cast operator the code doesn't compile; the compiler generate an error.

  POINT pt = { 10, 21 };
  unsigned char *pb = reinterpret_cast<unsigned char *>(&pt);
  // Print to screen the content of the structure in raw format
  for(int i = 0; i < sizeof(POINT); i++)
  printf("%02X ", pb[i]);

Finally, dynamic_cast is a polymorphic cast operator; it's used only with pointers, and its main property is that if the conversion is possible it return the pointer value, otherwise it returns NULL. It's useful when working with inheritance.