doesntwork.c

#include <stdnoreturn.h>
#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>

typedef enum {
    PUSH,
    POP,
    ADD,
    SUB,
    MUL,
    DIV,
    PRINT,
    FINISH,
} op_code;

typedef struct op {
    int32_t opcode;
    double arg;
} op;

typedef op program[];

typedef double stack[];

typedef noreturn void (*opfunc)(program, stack, double);

static noreturn void dispatch(program, stack);

static noreturn void push(program p, stack s, double arg)
{
    *s++ = arg;
    dispatch(p, s);
}

static noreturn void pop(program p, stack s, double arg)
{
    s--;
    dispatch(p, s);
}

static noreturn void add(program p, stack s, double arg)
{
    double b = *s--;
    double a = *s--;
    *s++ = a + b;
    dispatch(p, s);
}

static noreturn void sub(program p, stack s, double arg)
{
    double b = *s--;
    double a = *s--;
    *s++ = a - b;
    dispatch(p, s);
}

static noreturn void mul(program p, stack s, double arg)
{
    double b = *s--;
    double a = *s--;
    *s++ = a * b;
    dispatch(p, s);
}

static noreturn void opdiv(program p, stack s, double arg)
{
    double b = *s--;
    double a = *s--;
    *s++ = a / b;
    dispatch(p, s);
}

static noreturn void print(program p, stack s, double arg)
{
    printf("%f\n", *s);
    dispatch(p, s);
}

static noreturn void finish(program p, stack s, double arg)
{
    int rc = *s--;
    exit(rc);
}

static noreturn void dispatch(program p, stack s)
{
    static opfunc dispatch_table[] = {
        push,
        pop,
        add,
        sub,
        mul,
        opdiv,
        print,
        finish,
    };
    op nxt = *p++;
    dispatch_table[nxt.opcode](p, s, nxt.arg);
}

int main()
{
    program prog = {
        {PUSH, 1},
        {PUSH, 1},
        {ADD, 0},
        {PUSH, 2},
        {MUL, 0},
        {PRINT, 0},
        {PUSH, 0},
        {FINISH, 0},
    };
    double s[100];
    dispatch(prog, s);
}