Segmentation fault (core dumped) runtime error in C - c

Question

Hi so I am new to C and just wrote my first program in the language and keep getting the segmentation fault error when I try to run it. I'm sure there are multiple small mistakes I have made throughout the code. I have gone through it and I can't figure out where my mistake is. Here is my code:
// $Id: crpn.c,v 1.1 2013-10-22 13:28:04-07 - - $
#include <assert.h>
#include <libgen.h>
#include <stdio.h>
#include <stdlib.h>
int exit_status = EXIT_SUCCESS;
#define EMPTY (-1)
#define SIZE 16
typedef struct stack stack;
struct stack {
int top;
int capacity;
int size;
double numbers[SIZE];
};
void bad_operator (const char *oper) {
fflush (NULL);
fprintf (stderr, "oper=\"%s\"\n", oper);
fflush (NULL);
exit_status = EXIT_FAILURE;
printf("%s: invaild operator\n", oper);
}
void push (stack *the_stack, double number) {
if (the_stack->size == the_stack->capacity) {
printf("%a:stack overflow", number);
}
else {
the_stack->numbers[the_stack->size++]=number;
}
}
void do_binop (stack *the_stack, char oper) {
if ((the_stack->top)<1) {
printf("oper=\"%c\":stack underflow\n", oper);
}
else {
double right = the_stack->numbers[the_stack->size--];
double left = the_stack->numbers[the_stack->size--];
switch (oper) {
case '+': push (the_stack, left + right); break;
case '-': push (the_stack, left - right); break;
case '*': push (the_stack, left * right); break;
case '/': push (the_stack, left / right); break;
}
}
}
void do_print (stack *the_stack) {
if (the_stack->top == -1) {
printf("stack is empty\n");
}
else {
int pos;
for (pos = 0; pos <= the_stack->top; ++pos) {
printf("%a\n",the_stack->numbers[pos]);
}
}
}
void do_clear (stack *the_stack) {
the_stack->top = -1;
}
void do_operator (stack *the_stack, const char *oper) {
switch (oper[0] ) {
case '+': do_binop (the_stack, '+'); break;
case '-': do_binop (the_stack, '-'); break;
case '*': do_binop (the_stack, '*'); break;
case '/': do_binop (the_stack, '/'); break;
case ';': do_print (the_stack); break;
case '#': do_clear (the_stack); break;
default : bad_operator (oper); break;
}
}
int main (int argc, char **argv) {
if (argc != 1) {
fprintf (stderr, "Usage: %s\n", basename (argv[0]));
fflush (NULL);
exit (EXIT_FAILURE);
}
stack the_stack;
the_stack.top = EMPTY;
char buffer[1024];
for (;;) {
int scanrc = scanf ("%1023s", buffer);
if (scanrc == EOF) break;
assert (scanrc == 1);
if (buffer[0] == '#') {
scanrc = scanf ("%1023[^\n]", buffer);
continue;
}
char *endptr;
double number = strtod (buffer, &endptr);
if (*endptr == '\0') {
push (&the_stack, number);
}else if (buffer[1] != '\0') {
bad_operator (buffer);
}else {
do_operator (&the_stack, buffer);
}
}
return exit_status;
}

Answer 1

Let me "teach you to fish":
A debugger will tell you exactly where the fault is. If you're using an IDE (Xcode, Eclipse, VS) it has a nice interface to one and you should use that. If not:
Compile your program with the -g switch: gcc -g mycode.c. This adds debugging information to the executable (makes the debugger give you much better info).
$ gdb my_executable
...
> run
...
Segmentation fault
> where
This will give you the exact location (which function on which line number).

Answer 2

You're never initializing the_stack.size and the_stack.capacity.
stack the_stack;
the_stack.top = EMPTY;
the_stack.size = 0;
the_stack.capacity = SIZE;
It's also not clear what the intended difference between top and size is. The push function increments size, but do_binop and do_print use top, which is never incremented.

Answer 3

The problem is this, in your push() function:
the_stack->numbers[the_stack->size++]=number;
You never initialize the size member of your struct, so it's just random garbage, and you're going way out of bounds on the array. It also doesn't seem to make a lot of sense, since you also have a top member, which won't be updated if you do this. Seems like you should stick to either a top or a size member.