错误:预期标识符或'(''''''令牌之前

Question

AC

#include<stdio.h>
#include "a.h"

int main(){
        s.a = 10;
        printf("\n add : %d \n",add(2,2));
        printf("\n sub : %d \n",sub(2,2));
        printf("\n struct is : %d \n",s.a);
        return 0;
}

bc:

#include<stdio.h>
int add(int a,int b){
        return (a+b);
}
int sub(int a,int b){
        return (a-b);
}

啊:

#ifndef A_HEADER
#define A_HEADER

typedef struct _s{
        int a;
        int b;
}s;

int add(int a,int b);
int sub(int a,int b);

#endif

O/P:

[root@s new]# ls
a.c  a.h  b.c  include 

[root@s new]# gcc -c a.c -o a.o
a.c: In function ‘main’:
a.c:4: error: expected identifier or ‘(’ before ‘.’ token
a.c:7: error: expected expression before ‘s’

我上面收到了一个错误.找不到错误的原因

Answer 1

s是一种类型 - 您需要声明此类型的实例:

int main(){
    s my_s;       // my_s is an instance of the struct type `s`
    my_s.a = 10;  // initialise the `a` element of `my_s`
    printf("\n add : %d \n",add(2,2));
    printf("\n sub : %d \n",sub(2,2));
    printf("\n struct is : %d \n",my_s.a); // <<<
    return 0;
}