How many ways to create object(s) in C++?

Only heard of T a and new T()? You are not a REAL™ C++ programmer.

Checkout how many ways you can think of to create some objects.

Rules

• Write your snippet in snippet/**/*.hpp:
  • We will #include <stdlib.h> for you at the beginning.
  • It should have one (1) function definition named create:
  • You may use auxilliary typedef, function, etc.
  • You may NOT do anything irrelevent to the object creation.
  • You MUST use auto whenever possible.
  • The creation method should be universal - not just for our stub.
• Checkout main.cpp and see what is considered valid.
  • Remember, MAGIC_NUMBER is 114514.
• Two creation methods are considered identical if they:
  • are lexically the same (adding comments); or
  • are syntactically the same (adding parentheses); or
  • are (trivially) semantically the same (1+1 v.s. 2); or
  • are identical after preprocessor;
  • only differ quantitatively (repeating something)
• Two methods are NEVER considered identical if they:
  • call different constructors
• Dirty methods are allowed as long as they:
  • are not identical to previous methods;
  • are compilable by both g++ and clang++ on ubunut xenial;
  • don't triggering any warnings (-Wextra);
  • are not "evil" (rm -rf /*)
• Additional rules for single:
  • with template typename T;
  • of signature T ();
  • invoke the constructor of T exactly once (1);
    • copy-constructor and move-constructor are NOT included
  • return an instance of T.
• Additional rules for array:
  • with template typename T;
  • of signature void (check_t<T>), where check_t<T> = void (*)(size_t, T (*)[3]));
  • invoke the constructor of T exactly three (3) times
    • copy-constructor and move-constructor are NOT included
  • treat the three values equally (i.e., construct them the same way)
  • invoke the function pointer exactly once (1):
    • the first parameter should be the sizeof of the array
    • the second parameter should be the pointer to the created array

Example

snippet/single/named-default.hpp: c++ template <typename T> T create() { T a; return a; }

snippet/single/new-empty.hpp: c++ template <typename T> T create() { return *new T(); }

snippet/array/named-default.hpp: c++ template <typename T> void create(check_t check) { T a[3]; check(sizeof(a), &a); }

License

We don't want you to think about legal consequence every time before creating an object. This project is proudly licensed as Creative Commons Zero v1.0 Universal