Segmentation fault from referencing function of Pointer Object - c++

Question

alright, this is a bit complicated for me to understand but ill explain it simply. Right now I in the middle of making a parser. part of making that parser is to make a parse tree. the first code snip below is the class for the parse tree where the label is like the node itself. nonTerms is just an enum of non-terminal names. the children here can either be terminals(tokens in the tk[]) or another non-terminal(nodeTK in children[]).
node.h
enum nonTerms{
PARSER,
PROG,
BLOCK,
VARS,
STATS,
STAT,
MSTAT,
IN,
OUT,
IF_,
LOOP,
ASSIGN,
GOTO_,
LABEL,
R0_,
EXPR,
N_,
A_,
M_,
R_,
none = -1
};
class nodeTK{
public:
nonTerms label;
std::vector<int> printOrder;
int tkIndex = 0;
Token* tk[5] = {nullptr, nullptr, nullptr, nullptr, nullptr};
int ntIndex = 0;
nodeTK* children[4] = {nullptr, nullptr, nullptr, nullptr};
nodeTK(); // creates a null node
nodeTK(nonTerms); //creates a node with specified nonterminal name
void pushTk(Token); //adds a token to the tk[]
void pushChild(nodeTK*); // adds a child to the children[]
nonTerms getLabel(); // returns the label of the current node
std::string printLabel(); // prints the string equivalent of the label
Token* getTk(int); // retrieves a specific tk in current node
nodeTK* getChild(int); // retrieves a child from current node
};
node.cpp
std::string myLabels[21] = {
"PARSER",
"PROG",
"BLOCK",
"VARS",
"STATS",
"STAT",
"MSTAT",
"IN",
"OUT",
"IF",
"LOOP",
"ASSIGN",
"GOTO",
"LABEL",
"R0",
"EXPR",
"N",
"A",
"M",
"R",
"none"
};
nodeTK::nodeTK(){
label = none;
}
nodeTK::nodeTK(nonTerms non_terminal){
std::cout << non_terminal << std::endl;
label = non_terminal;
}
void nodeTK::pushTk(Token token){
if(tkIndex < 5){
printOrder.push_back(1);
tk[tkIndex] = &token;
tkIndex++;
}else{
std::cout << "your pushing too many tokens in this node with tk " << token.getInstance() << std::endl;
}
}
void nodeTK::pushChild(nodeTK* nodeChild){
if(ntIndex < 4){
printOrder.push_back(0);
children[ntIndex] = nodeChild;
std::cout << children[ntIndex]->getLabel() << std::endl;
ntIndex++;
}
else{
std::cout << "your pushing too many non-terminals in this node" << std::endl;
}
}
nonTerms nodeTK::getLabel(){
std::cout << "hello" << std::endl;
return label;
}
std::string nodeTK::printLabel(){
std::string str = myLabels[label];
return str;
}
Token* nodeTK::getTk(int index){
return tk[index];
}
nodeTK* nodeTK::getChild(int index){
return children[index];
}
void nodeTK::preOrder(){
std::cout << printLabel() << std::endl;
int tkIndex = 0;
int childIndex = 0;
for(int i = 0; i < printOrder.size(); i++){
if(printOrder.at(i) == 1){
std::cout << getTk(tkIndex)->getInstance() << std::endl;
tkIndex++;
}else if(printOrder.at(i) == 0){
nodeTK * temp;
std::cout << getChild(childIndex)->getLabel() << std::endl;
childIndex++;
}else{
std::cout << "something went wrong" << std::endl;
}
}
}
this is where the issue is. As you can see this function receives a node pointer which I then assign to one of the still null children in the children[]. all I want to do is print the label of the child node after it has received the pointer to check that it was retrieved correctly. getLabel() should return an enumerated value and the cout should just output some number. Every time I attempt to run getLabel() in the program ends with a segmentation fault at exactly that function call. I know it partly runs because I put some dummy cout statements to see if the function runs and the couts to appear in the terminal. I'm not sure exactly what I'm doing wrong though. Sorry if my question is not super clear, I feel like I'm still a noob to pointers.
void nodeTK::pushChild(nodeTK* nodeChild){
if(ntIndex < 4){
printOrder.push_back(0);
children[ntIndex] = nodeChild;
std::cout << children[ntIndex]->getLabel() << std::endl;
ntIndex++;
}
else{
std::cout << "your pushing too many non-terminals in this node" << std::endl;
}
}
here's the getLabel function:
nonTerms nodeTK::getLabel(){
std::cout << "hello" << std::endl;
return label;
}
here's the output of the code.
hello
Segmentation fault
thank you again