為什么即使包含標頭我也會收到這些警告？

Question

GCC 發出警告，這對我來說毫無意義。 我已經包含了所需的stdio庫。 該程序的執行按預期工作，我在 EDX 上也獲得了 100% 的分數。 還有關於size 6和size 5的這些警告是什么？

到目前為止的代碼：

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

struct student {
      char name[50];
      int age;
      struct student *next;
};

struct student *createStudent(char studentName[50], int studentAge);
struct student * append(struct student * end, struct student * newStudptr);
void printStudents(struct student *start);
void copyStr(char [], char []);
/* add other prototypes here if needed*/

int main(void) {
    struct student *start, *newStudptr, *end, *tmp;
    int ageP, ageR, ageM;

    scanf("%d %d %d", &ageP, &ageR, &ageM);

    start = createStudent("Petra", ageP);
    end = start;

    newStudptr = createStudent("Remi", ageR);
    end = append(end, newStudptr);

    newStudptr = createStudent("Mike", ageM);
    end = append(end, newStudptr);

    printStudents(start);
    tmp = start->next;

    free(start);

    start = tmp;
    tmp = start->next;

    free(start);
    free(tmp);

    return 0;
}

struct student* createStudent(char studentName[50], int studentAge) {
    struct student* newStud;

    newStud = (struct student*) malloc(sizeof(struct student));

    copyStr(studentName, newStud->name);
    newStud->age = studentAge;
    newStud->next = NULL;

    return newStud;
}

struct student* append(struct student* end, struct student* newStudPtr) {
    end->next = newStudPtr;
    end = newStudPtr;

    return end;
}

void copyStr(char source[], char target[]) {
    int i = 0;

    while(source[i] != '\0') {
        target[i] = source[i];
        i++;
    }

    target[i] = '\0';
}

void printStudents(struct student* start) {
    struct student* ptr = start;

    while(ptr != NULL) {
        printf("%s is %d years old.\n", ptr->name, ptr->age);
        ptr = ptr->next;
    }
}

/* Place your function definitions here. Be sure to include the definitions for 
   createStudent() and append() as well as any other functions you created for 
   the previous tasks. */

警告：

:!gcc -Wall -std=c17 edx_PrintLinkedList.c -o bin/edx_PrintLinkedList                                                                                                                 
edx_PrintLinkedList.c: In function ‘main’:
edx_PrintLinkedList.c:22:13: warning: ‘createStudent’ accessing 50 bytes in a region of size 6 [-Wstringop-overflow=]
   22 |     start = createStudent("Petra", ageP);
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
edx_PrintLinkedList.c:22:13: note: referencing argument 1 of type ‘char *’
edx_PrintLinkedList.c:45:17: note: in a call to function ‘createStudent’
   45 | struct student* createStudent(char studentName[50], int studentAge) {
      |                 ^~~~~~~~~~~~~
edx_PrintLinkedList.c:25:18: warning: ‘createStudent’ accessing 50 bytes in a region of size 5 [-Wstringop-overflow=]
   25 |     newStudptr = createStudent("Remi", ageR);
      |                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~
edx_PrintLinkedList.c:25:18: note: referencing argument 1 of type ‘char *’
edx_PrintLinkedList.c:45:17: note: in a call to function ‘createStudent’
   45 | struct student* createStudent(char studentName[50], int studentAge) {
      |                 ^~~~~~~~~~~~~
edx_PrintLinkedList.c:28:18: warning: ‘createStudent’ accessing 50 bytes in a region of size 5 [-Wstringop-overflow=]
   28 |     newStudptr = createStudent("Mike", ageM);
      |                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~
edx_PrintLinkedList.c:28:18: note: referencing argument 1 of type ‘char *’
edx_PrintLinkedList.c:45:17: note: in a call to function ‘createStudent’
   45 | struct student* createStudent(char studentName[50], int studentAge) {

Answer 1

我們不知道您可以更改哪些線路

但是 gcc 正在抱怨這個

你說

   struct student* createStudent(char studentName[50], int studentAge)

但后來你做了

   start = createStudent("Petra", ageP);

它試圖調用它作為

  struct student* createStudent(char studentName[6], int studentAge)

function

你可以做

  struct student* createStudent(char studentName[], int studentAge)

那可行

編輯

---

你也可以這樣修

  char name[50];
  ....
  strcpy(name, "Petra");
  start = createStudent(name, ageP);