What is the meaning of this error??

Question

I am creating an program for parenthesis matching in C using stack, but i am getting an error .
https://code.sololearn.com/cPcXK5PIJoPY/?ref=app

Answer 1

Rei ,you are absolutely right.

Vinayak Dutt , you are only declaring a pointer of type (struct stack), you have to make it point to something.

Here is the fix👇
https://code.sololearn.com/cQZfTWLQEFlq/?ref=app

Answer 2

Thank you Arsenic and Rei

Answer 3

i'm not good with C but my guess is *sp is not pointing to any memory, so maybe do this
struct stack *sp = malloc(sizeof(struct stack));