Second stack prints blank using GList

Question

I'm implementing this data structure (infix to postfix) using stack.

Basically, I'm testing with push and print, no pop operation. The first stack ie., stack holds the operator and numbers while the second stack stack_precedence records precedence. I think both stacks work fine but I don't understand why precedence stack is not printing the precedence numbers and instead returns blank output.

Partial implementation:

#include <iostream>
#include <glib.h>

using namespace std;

int main(int argc, char *argv[])
{
        GList *stack = nullptr;
        GList *stack_precedence = nullptr;

        int size = 0;
        for (int i = 0; argv[1][i] != '\0'; i++) {
                int precedence = 0;
                bool is_precedence_set = false;
                switch (argv[1][i]) {
                /*
                 * Precedence order:
                 * 3) ^
                 * 2) / *
                 * 1) + -
                 * 0) ( )
                 */
                case '^':
                        precedence = 3;
                        is_precedence_set = true;
                case '/':
                case '*':
                        if (!is_precedence_set) {
                                precedence = 2;
                                is_precedence_set = true;
                        }
                case '+':
                case '-':
                        if (!is_precedence_set) {
                                precedence = 1;
                                is_precedence_set = true;
                        }
                case '(':
                        if (!is_precedence_set) {
                                precedence = 0;
                                is_precedence_set = true;
                        }

                        stack = g_list_append(
                                        stack, GINT_TO_POINTER(argv[1][i]));
                        stack_precedence = g_list_append(
                                        stack_precedence, GINT_TO_POINTER(precedence));
                        size++;
                        break;
                case ')':
                        if (!is_precedence_set) {
                                precedence = 0;
                                is_precedence_set = true;
                        }
                        break;
                default:
                        if (argv[1][i] >= '0' and argv[1][i] <= '9') {
                                precedence = 9;
                                stack = g_list_append(
                                                stack, GINT_TO_POINTER(argv[1][i]));
                                stack_precedence = g_list_append(
                                                stack_precedence, GINT_TO_POINTER(precedence));
                                size++;
                        }
                }
        }

        cout << "Stack size: " << size << endl;

        stack = g_list_first(stack);
        while (stack != nullptr) {
                char c = GPOINTER_TO_INT(stack->data);
                cout << c;
                stack = g_list_next(stack);
        }
        cout << endl;

        stack_precedence = g_list_first(stack_precedence);
        while (stack_precedence != nullptr) {
                char c = GPOINTER_TO_INT(stack_precedence->data);
                cout << c;
                stack_precedence = g_list_next(stack_precedence);
        }
        cout << endl;

        return 0;
}

I pass in 2+2 as an argument to my program and stack works printing 2+2 exactly but stack_precedence returns blank.

My expected outcome is

2+2
919

And not

2+2
blank

Answer 1

Precedences are integers not characters

int c = GPOINTER_TO_INT(stack_precedence->data);
^^^ change here