C++ static_cast

Table of contents

::: important Prefer C++ casts over C- style casts

• C++ casts, static_cast<> is jut one of them, make your intent very clear
• They are easy to search for in code
• static_cast<>() is checked by the compiler, and if the types are not

  double x{12.5};
  double y{34.6};

  unsigned char cc[] = {0, 0, 0, 0};

  auto sum1 = static_cast<int>(x) + static_cast<int>(y);
  auto sum2 = static_cast<int>(x + y);

  fmt::print("sizeof(sum1) = {} sum1 = {} <- (12+34)\n", sizeof(sum1), sum1);
  fmt::print("sizeof(sum2) = {} sum2 = {} <- (47.1)\n", sizeof(sum2), sum2);

  fmt::print("{} {} {} {} {}\n", static_cast<int>(*cc), cc[0], cc[1], cc[2],
             cc[3]);

  cc[1] = 254;  // this does not affect the static_cast below
  fmt::print("{} {} {} {} {}\n", static_cast<int>(*cc), cc[0], cc[1], cc[2],
             cc[3]);
  cc[0] = 14;
  fmt::print("{} {} {} {} {}\n", static_cast<int>(*cc), cc[0], cc[1], cc[2],
             cc[3]);

  fmt::print("Buffer overflow\n");
  unsigned char c = 253;
  for (int i = 0; i < 5; ++i) {
    fmt::print("i: {} -> {}\n", i, static_cast<int>(++c));
  }

  fmt::print("Buffer underflow\n");
  for (int i = 0; i < 5; ++i) {
    fmt::print("i: {} -> {}\n", i, static_cast<int>(--c));
  }

Possible output

sizeof(sum1) = 4 sum1 = 46 <- (12+34)
sizeof(sum2) = 4 sum2 = 47 <- (47.1)
0 0 0 0 0
0 0 254 0 0
14 14 254 0 0
Buffer overflow
i: 0 -> 254
i: 1 -> 255
i: 2 -> 0
i: 3 -> 1
i: 4 -> 2
Buffer underflow
i: 0 -> 1
i: 1 -> 0
i: 2 -> 255
i: 3 -> 254
i: 4 -> 253

References

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