C++ OOP private variable changes the value itself - c++

Question

So I programmed a simple lexer which I currently studying is Language Implementation Patterns.
The codes in the said book is written in JAVA and I've tried to code it using C++.
It just have to recognized the tokens i provided in the program for example and spaces will be skipped:
'[ABCDE , EFGH]'
[ - LBRACK
ABCDE - NAME
, - COMMA
EFGH - NAME
So I build different classes as I convert the classes in JAVA to C++.
Token.h
#pragma once
#include <string>
#include <vector>
using namespace std;
constexpr auto NAME = 2;
constexpr auto COMMA = 3;
constexpr auto LBRACK = 4;
constexpr auto RBRACK = 5;
class Token
{
public:
Token();
~Token();
Token(int , const char * text );
char * to_string();
string tokenNames[6] = { "n/a" , "<EOF>", "NAME", "COMMA", "LBRACK", "RBRACK" };
int token_type() { return this->type; }
private:
int type = 0;
char * text = NULL;
};
Token.cpp
#include "Token.h"
Token::Token() {
}
Token::~Token(){
}
Token::Token(int type, const char * text) {
this->text = (char *)text;
this->type = type;
}
char* Token::to_string() {
char* out_buffer = new char[255];
vector <string> tokenNames;
int size = sizeof(this->tokenNames) / sizeof(this->tokenNames[0]);
for (int i = 0; i <size; i++)
{
tokenNames.push_back(this->tokenNames[i]);
}
printf("%s", this->text);
sprintf(out_buffer, "%s , %s \n", this->text, tokenNames[this->type].c_str());
return out_buffer;
}
Lexer.h
#pragma once
#include <string>
#include <vector>
#include "Token.h"
#define EOF -1
constexpr auto EOF_TYPE = 1;;
using namespace std;
class Lexer
{
public:
Lexer();
~Lexer();
Lexer(vector <char> input);
void consume();
void match(char x);
char get_c() {
return c;
}
vector<char> input;
char c;
private:
int p = 0;
};
Lexer.cpp
#include "Lexer.h"
Lexer::Lexer()
{
}
Lexer::~Lexer()
{
}
Lexer::Lexer(vector <char> input) {
this->input = input;
c = input.at(p);
}
void Lexer::consume() {
p++;
if (p >= this->input.size()) c = EOF;
else c = this->input.at(p);
}
void Lexer::match(char x) {
if (this->c == x) consume();
else throw "wrong input";
}
ListLexer.h
#pragma once
#include <vector>
#include "Token.h"
#include "Lexer.h"
class ListLexer : public Lexer, Token
{
public:
ListLexer();
~ListLexer();
Lexer* lexer;
ListLexer(vector <char> x) {
lexer = new Lexer(x);
c = lexer->get_c();
}
char* get_token_names(int x);
Token* next_token();
void skip_space();
bool is_letter();
char * name();
private:
char c = NULL;
};
ListLexer.cpp
#include "ListLexer.h"
ListLexer::ListLexer()
{
c = lexer->c;
}
ListLexer::~ListLexer()
{
}
char* ListLexer::get_token_names(int x) {
char out_buffer[100];
sprintf(out_buffer, "%s", Token::tokenNames[x]);
return out_buffer;
}
Token* ListLexer::next_token() {
while ((c= lexer->c) != EOF) {
switch (c) {
case ' ': case '\t': case '\n': case '\r': skip_space(); continue;
case '[':
lexer->consume();
return new Token(LBRACK, "LBRACK");
case ']':
lexer->consume();
return new Token(RBRACK, "RBRACK");
case ',':
lexer->consume();
return new Token(COMMA, "COMMA");
default:
if (is_letter()) return new Token(NAME, name());
throw "wrong input";
}
}
return new Token(EOF_TYPE, "EOF");
}
void ListLexer::skip_space() {
while (c == ' ' || c == '\t' || c == '\n' || c == '\r')
consume();
}
bool ListLexer::is_letter() {
return (lexer->c >= 'a' && lexer->c <= 'z') || (lexer->c >= 'A' && lexer->c <= 'Z');
}
char* ListLexer::name() {
vector <char> buffer;
char out_buffer[255];
while (is_letter()) {
buffer.push_back(lexer->c);
lexer->consume();
}
buffer.push_back('\x00');
std::copy(buffer.begin(), buffer.end(), out_buffer);
printf("%s", out_buffer);
return out_buffer;
}
main.cpp
#include <stdio.h>
#include <vector>
#include "Token.h"
#include "Lexer.h"
#include "ListLexer.h"
using namespace std;
int main(int argc, char* argv[])
{
vector <char> vec;
vec.push_back('a');
vec.push_back('b');
vec.push_back('c');
vec.push_back('d');
vec.push_back(',');
vec.push_back('e');
vec.push_back('f');
vec.push_back('g');
vec.push_back('h');
vec.push_back('\xff');
ListLexer* listlexer = new ListLexer(vec);
try {
Token* t = listlexer->next_token();
while (t->token_type() != EOF_TYPE)
{
printf("%s", t->to_string());
t = listlexer->next_token();
}
printf("%s", t->to_string());
}
catch (const char * e) {
printf("Error: %s \n", e);
}
return 0;
}
However, everytime it calls the t->to_string(), the value of text which is should be name "ABCD" or "EFGH" is different.
The highlighted figures are from the ListLexer::name().
The value of the text which is private from the instantiated token class is modified.
Did I miss something? Please help me. Im just learning OOP through this.