c - 获取结构体数组内结构体的值

Question

typedef struct{
  int number;
  char name[100];
} Apple

typedef struct{
  Apple *apple;
  int bit[2];
} AppleArray;

int main(){
  AppleArray *aArray;
  loadApple(&aArray);
}

loadApple(AppleArray **aArray){
  *aArray = NULL;
  for(i=0; i<100; i++){
    *aArray = realloc(*aArray, (i+1) * sizeof(AppleArray));

    /*SEGFAULT here*/
    aArray[i]->apple = NULL;

    for(j=0; j<2; j++){
      aArray[i]->apple = realloc(aArray[i]->apple, sizeof(Apple) * (j+1))
    }
  }

}

我想要一个具有特定大小的AppleArray。每个 AppleArray 将有两个 Apple。但是，当我将 NULL 分配给 aArray[i]->apple 时，出现段错误。那里有什么问题？

编辑:

loadApple(AppleArray **aArray){
  *aArray = malloc(100 * sizeof(AppleArray));
  for(i=0; i<100; i++){

    /*SEGFAULT here*/
    aArray[i]->apple = NULL;

    for(j=0; j<2; j++){
      aArray[i]->apple = realloc(aArray[i]->apple, sizeof(Apple) * (j+1))
    }
  }
}

Answer 1

您可以调用realloc()仅在由先前的内存分配函数返回给您的地址上，例如 malloc()或calloc()否则它会给你未定义的行为。

C99 标准 7.20.3.4-3:realloc 函数:

void *realloc(void *ptr, size_t size);

If ptr is a null pointer, the realloc function behaves like the malloc function for the specified size. Otherwise, if ptr does not match a pointer earlier returned by a memory management function, or if the space has been deallocated by a call to the free or realloc function, the behavior is undefined.