Wat in C++

wat.cpp

// http://madebyevan.com/obscure-cpp-features/
// ptr[3] is *(ptr + 3) and is therefore 3[ptr]

// Is this:
// 1) A variable of type std::string initialized to a std::string()?
// 2) The declaration of a function that returns a std::string and has one argument,
//    which is a pointer to a function with no arguments that returns a std::string?
std::string foo(std::string());

// Is this:
// 1) A variable of type int initialized to int(x)?
// 2) The declaration of a function that returns an int and has one argument,
//    which is an int named x?
int bar(int(x));

// Parentheses resolve the ambiguity
std::string foo((std::string()));
int bar((int(x)));

// Redefining keywords via the preprocessor is technically supposed to cause an error but tools allow it in practice
#define class struct
#define private public
#define protected public

// Placement new 
#include <iostream>
using namespace std;

struct Test {
  int data;
  Test() { cout << "Test::Test()" << endl; }
  ~Test() { cout << "Test::~Test()" << endl; }
};

int main() {
  // Must allocate our own memory
  Test *ptr = (Test *)malloc(sizeof(Test));

  // Use placement new
  new (ptr) Test;

  // Must call the destructor ourselves
  ptr->~Test();

  // Must release the memory ourselves
  free(ptr);

  return 0;
}