I use the C/C++ extension for VSCode and I wanted to give a shot to c23, gcc does recognize nullptr but the VSCode IDE doesn't, and even tho my code works, I dont like the error message in the IDE. Any solutions??

I'm making a basic stack class. But I haven't used generics before, and I'm seeing all sorts of weird errors when I try to compile.

Stack.h:

//My name

#include "StackNode.h"

template <class T> class Stack {
	public:
		void push(T const&);
		T pop();
		T peek() const;
		void clear();
		bool isEmpty() const;
	private:
		StackNode<T>* top;
		void clearHelper(StackNode<T>* start);
};

Stack.cpp:

//My name

#include "Stack.h"

template <class T> void Stack<T>::push(T const& val) {
	StackNode<T>* newNode(val, top);
	top = newNode;
}

template <class T> T Stack<T>::pop() {
	if(top == nullptr) {
		return nullptr;
	}
	T tempaT = top.getValue();
	StackNode<T>* tempNode = top;
	top = tempNode.getPrev();
	delete tempNode;
	return tempaT;
}

template <class T> T Stack<T>::peek() const {
	if(top == nullptr) {
		return nullptr;
	} else {
		return top.getValue();
	}
}

void Stack<T>::clear() {
	if(top == nullptr) {return;}
	clearHelper(top);
	top = nullptr;
}

void Stack<T>::clearHelper(StackNode<T>* start) {
	if(start == nullptr) {
		return;
	} else {
		clearHelper(start.getPrev());
		delete start;
	}
}

bool Stack<T>::isEmpty() const {
	return top == nullptr;
}

The errors are as follows. I can't even find other people with the nullptr error.

Stack.cpp:11:12: error: use of undeclared identifier 'nullptr'
        if(top == nullptr) {
                  ^
Stack.cpp:12:10: error: use of undeclared identifier 'nullptr'
                return nullptr;
                       ^
Stack.cpp:14:16: error: member reference base type 'StackNode<T> *' is not a structure or union
        T tempaT = top.getValue();
                   ~~~^~~~~~~~~
Stack.cpp:16:16: error: member reference base type 'StackNode<T> *' is not a structure or union
        top = tempNode.getPrev();
              ~~~~~~~~^~~~~~~~
Stack.cpp:22:12: error: use of undeclared identifier 'nullptr'
        if(top == nullptr) {
                  ^
Stack.cpp:23:10: error: use of undeclared identifier 'nullptr'
                return nullptr;
                       ^
Stack.cpp:25:13: error: member reference base type 'StackNode<T> *const' is not a structure or union
                return top.getValue();
                       ~~~^~~~~~~~~
Stack.cpp:29:12: error: use of undeclared identifier 'T'
void Stack<T>::clear() {
           ^
Stack.cpp:29:16: warning: extra qualification on member 'clear' [-Wextra-qualification]
void Stack<T>::clear() {
               ^
Stack.cpp:29:16: error: out-of-line definition of 'clear' does not match any declaration in the global namespace
void Stack<T>::clear() {
               ^~~~~
Stack.cpp:30:5: error: use of undeclared identifier 'top'
        if(top == nullptr) {return;}
           ^
Stack.cpp:30:12: error: use of undeclared identifier 'nullptr'
        if(top == nullptr) {return;}
                  ^
Stack.cpp:31:14: error: use of undeclared identifier 'top'
        clearHelper(top);
                    ^
Stack.cpp:32:2: error: use of undeclared identifier 'top'
        top = nullptr;
        ^
Stack.cpp:32:8: error: use of undeclared identifier 'nullptr'
        top = nullptr;
              ^
Stack.cpp:35:12: error: use of undeclared identifier 'T'
void Stack<T>::clearHelper(StackNode<T>* start) {
           ^
Stack.cpp:35:38: error: use of undeclared identifier 'T'
void Stack<T>::clearHelper(StackNode<T>* start) {
                                     ^
Stack.cpp:35:38: error: use of undeclared identifier 'T'
Stack.cpp:35:16: warning: extra qualification on member 'clearHelper' [-Wextra-qualification]
void Stack<T>::clearHelper(StackNode<T>* start) {
               ^
Stack.cpp:36:14: error: use of undeclared identifier 'nullptr'
        if(start == nullptr) {
                    ^
Stack.cpp:44:12: error: use of undeclared identifier 'T'
bool Stack<T>::isEmpty() const {
           ^
Stack.cpp:44:16: warning: extra qualification on member 'isEmpty' [-Wextra-qualification]
bool Stack<T>::isEmpty() const {
               ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
3 warnings and 20 errors generated.

Hello,

I'm writing a program in which it generates a random number between 0-100 and the user has to guess. The program will respond with whether or not their guess is correct, too high, or too low, etc. However, in putty my source code is not compiling with the error lab2.cpp:13: error: 'nullptr' was not declared in this scope lab2.cpp:35: error: expected ';' before '}' token

My code is as follows:

#include <iostream>
#include <cstdlib>
#include <ctime>

using namespace std;

int main()
{
int n = 0;
bool do_more = true;

srand(time(nullptr));
int target = rand() % 100 + 1;
cout << "Welcome to the number guessing game! " << endl;
cout << "Please enter your guess, between 0 and 100. " <<     endl;

do {
	cout << "Enter your guess: ";
	cin >> n;
	if (n == 0) {
		cout << "Bye! ";
		do_more = false;
	}
	else if (n > target) {
		cout << "Guess is too high! Try again! " << endl;
	}
	else if (n < target) {
		cout << "Guess is too low. Try again! " << endl;
	}
	else {
		cout << "You win! ";
		cout << "Answer is " << n << endl;
		do_more = false;
		}
} while (do_more);
return 0;
}

Thanks in advance for any help with this confusing error.

Sorry if this question is really simple, but I've been trying to find out if (x > x), (x < x), (x >= x) and (x <= x) where one x is nullptr and the other x is a valid pointer is undefined behavior. I've been trying to test it with "-fsanitize=undefined" and it hasn't complained so far. So I just wanted some confirmation from people who know way more than me.

So for example, does this test code invoke undefined behavior?

#include <iostream>

struct CheckStatus
{
    bool first = false;
    bool second = false;
    bool third = false;
    bool fourth = false;
};

[[nodiscard]] CheckStatus Check()
{
    CheckStatus cs;
    char c1('a');
    char* cp1(&c1);
    char* cp2(nullptr);
    
    if(cp1 < cp2) cs.first = true;
    if(cp1 > cp2) cs.second = true;
    if(cp1 <= cp2) cs.third = true;
    if(cp1 >= cp2) cs.fourth = true;
    
    return cs;
}

int main()
{
    CheckStatus cs(Check());
    
    if(cs.first) std::cout << "1st: true" << std::endl;
    if(cs.second) std::cout << "2nd: true" << std::endl;
    if(cs.third) std::cout << "3rd: true" << std::endl;
    if(cs.fourth) std::cout << "4th: true" << std::endl;
    
    return 0;
}

(In case for some reason the code isn't formatted correctly for you, please see it here: "https://pastebin.com/nNetU7pu")