A minimalistic VM in C

main.c

#include "tvm.c"

int main(void)
{
    int code[] = {
        Const,
        -5564,
        Const,
        184841,
        Add,
        Print,
        Exit,
    };
  
    execute(code);

    return 0;
}

tvm.c

#include <stdio.h>

enum {
    Const,
    Add,
    Sub,
    Jeq,
    Jne,
    Load,
    Store,
    Print,
    Exit
};

#define STACK_SIZE 1024

#define push(val) stack[sp++] = val
#define pop() stack[--sp]

int execute(int* code)
{
    int stack[STACK_SIZE];
    int mem[512];
    int pc = 0, sp = 0;

    int x, y, n;
    while (1) {
        switch (code[pc]) {
        case Const:
            push(code[++pc]);
            break;
        case Add:
            x = pop();
            y = pop();
            push(x + y);
            break;
        case Sub:
            x = pop();
            y = pop();
            push(x - y);
            break;
        case Jeq:
            x = pop();
            y = pop();
            n = pop();
            if (x == y)
                pc += n;
            break;
        case Jne:
            x = pop();
            y = pop();
            n = pop();
            if (x != y)
                pc += n;
            break;
        case Load:
            n = pop();
            push(mem[n]);
            break;
        case Store:
            x = pop();
            n = pop();
            mem[n] = x;
            break;
        case Print:
            x = pop();
            printf("%d\n", x);
            break;
        case Exit:
            return stack[pc];
        }
        pc++;
    }

    return stack[sp];
}