c - 错误: Syntax error before 'struct'

Question

我的代码基本上是用于创建/使用堆栈的函数。我几乎尝试了所有方法，但我不知道为什么我的程序显示此错误:

Error: Syntax error before 'struct'

#include "stack.h"

#include <stdio.h>
#include <stdlib.h>
#define CAPACITY 128

struct stack_struct {
    ElemType items[CAPACITY];
    int top;
};


StackPtr stk_create(){
    StackPtr s = malloc(sizeof(struct stack_struct));

    s->top = -1;  // stack initially empty
    return s;
}

// TODO
StackPtr stk_clone(StackPtr s) {
  return NULL;  // temporary placeholder
}

void stk_free(StackPtr s) {
    free(s);
}

int stk_push(StackPtr s, ElemType val){
    if(s->top == CAPACITY - 1)
     struct stack_struct * temp;
    temp = (struct stack_struct*)malloc(sizeof(struct stack_struct));
    s->top++;
    s->items[s->top] = val;
    return 1;
}

ElemType stk_pop(StackPtr s){
    if(s->top == -1)
        abort();  // library function which terminates program!!!
    s->top--;
    return s->items[s->top+1];
}

int stk_is_full(StackPtr s){
    return s->top == CAPACITY-1;
}

int stk_is_empty(StackPtr s){
    return s->top == -1;
}

int stk_size(StackPtr s) {
    return s->top+1;
}

void stk_clear(StackPtr s){
    s->top = -1;
}

void stk_print(StackPtr s) {
    int i;
    printf("\n----TOP-----\n");

    for(i=s->top; i>=0; i--) {
        printf(FORMAT_STRING, s->items[i]);
    }
    printf("---BOTTOM---\n");
}

int main() {

    StackPtr sptr;

    sptr = stk_create();

    stk_push(sptr, 1.7);
    stk_push(sptr, 3.14);
    stk_print(sptr);

    stk_pop(sptr);

    stk_print(sptr);

    stk_free(sptr);

}

Answer 1

正如我所见，函数 stack_push 应该如下所示

int stk_push(StackPtr s, ElemType val){
    if(stk_is_full(s))
       return -1; // stack already full, we couldn't push new elem
    s->top++;
    s->items[s->top] = val;
    return 1;
}