Use smart-pointer and generate C++ code for bison/flex/bnfc

[hangingman]

ref #293

PR description:
I modified C++ code related with issue #293 .

PR contents

• Makefile changes:

  • If bnfc received --ansi flag, Makefile would have -std=c++14 compile option otherwise --ansi.
  • If bnfc not received --ansi flag, bnfc will generate .ll and .yy files

• Fix PARSER_HEADER_FILE

  • C++ source should have same name interface like "psProgram" in header file and source file. But, currently it looks Parser.H doesn't match function name.

• C++ AST/Test code generator switching

  • If bnfc not received --ansi flag, bnfc would genrate codes using smart-pointer (std::unique_ptr), otherwise bnfc generate codes same as before.

Sample code:

use using instead of typedef

/********************   TypeDef Section    ********************/

using Integer = int;
using Char = char;
using Double = double;
using String = std::string;
using Ident = std::string;

clone() returns instance wrapped std::unique_ptr

/********************   Abstract Syntax Classes    ********************/

class Program : public Visitable
{
public:
  virtual std::unique_ptr<Program> clone() const = 0;
};

• Impl classes have each copy constructors
  • I referred the book "More Effective C++" to implement it.

class Prog : public Program
{
private:
  std::unique_ptr<ListStatement> liststatement_;

public:
  // for "std::move"
  Prog(Prog&& rhs);
  Prog& operator=(Prog&& rhs);
  // for normal copy
  Prog(const Prog& rhs);
  Prog& operator=(const Prog& rhs);
  Prog(const ListStatement& p1);
  ~Prog();
  virtual void accept(Visitor *v);
  std::unique_ptr<Program> clone() const override;
};

• [WIP] Bison/Flex code genrator switching

  • Still work in progress, but code might require Bison3.2
  • I think I will modify process switching some code in bison

• Use smart pointer in test C++ source

  • This enables test.C to use unique_ptr, however this is just a example. I think this kind of smart-pointer can apply for other C++ code generated by bnfc also. To use smart pointer, I added #include <memory>.
  • will generate following code

  if (parse_tree)
  {
    printf("\nParse Successful!\n");
    if (!quiet) {
      printf("\n[Abstract Syntax]\n");
      std::unique_ptr<ShowAbsyn> s(new ShowAbsyn());
      printf("%s\n\n", s->show(parse_tree));
      printf("[Linearized Tree]\n");
      std::unique_ptr<PrintAbsyn> p(new PrintAbsyn());
      printf("%s\n\n", p->print(parse_tree));
    }
    delete(parse_tree);
    return 0;
  }