在c中以数组作为变量的结构

i need to create a data type (struct in this case) with an array as a property. I have an initialiser function that initialises this data structure and gives the array a specified size. The problem now is declaring the array in the struct. for example "int values[]" will require that I enter a number in the brackets eg values[256]. Th3 256 should be specified wen the structure is initialised. Is there a way I get around this?

我需要创建一个数据类型(本例中为struct)，其中数组作为属性。我有一个initialiser函数，它初始化这个数据结构并给数组一个指定的大小。现在的问题是在结构体中声明数组。例如，“int values[]”要求我在括号中输入数字eg values[256]。当结构被初始化时，应该指定th3256。我有办法解决这个问题吗?

typedef struct 
{
        int values[];      //error here
        int numOfValues;
} Queue;

3 个解决方案

#1

A struct must have a fixed size known at compile time. If you want an array with a variable length, you have to dynamically allocate memory.

结构体必须在编译时具有已知的固定大小。如果想要一个可变长度的数组，就必须动态地分配内存。

typedef struct {
    int *values;
    int numOfValues;
} Queue;

This way you only have the pointer stored in your struct. In the initialization of the struct you assign the pointer to a memory region allocated with malloc:

这样，您就只能将指针存储在结构体中。在struct的初始化过程中，将指针分配给分配给malloc的内存区域:

Queue q;
q.numOfValues = 256;
q.values = malloc(256 * sizeof(int));

Remember to check the return value for a NULL pointer and free() any dynamically allocated memory as soon as it isn't used anymore.

记住，要检查空指针的返回值，并在不再使用任何动态分配内存时检查free()。

#2

#include<stdio.h> 
#include<stdlib.h>
typedef struct Queue {
int numOfValues;
int values[0]; 
} Queue_t;

int main(int argc, char **argv) {
Queue_t *queue = malloc(sizeof(Queue_t) + 256*sizeof(int));
return (1);
}

This way you can declare 'variable length arrays'. And you can access your array 'values' with queue->values[index]

这样就可以声明“可变长度数组”。您可以使用队列->值来访问数组的值[索引]

EDIT: Off course you need to make sure that once you free you take into account the 'n*sizeof(int)' you have allocated along with sizeof(Queue_t) where n=256 in the above example HTH

编辑:Off course，你需要确保一旦你*了，你就会考虑到“n*sizeof(int)”，你已经和sizeof(Queue_t)一起分配了，在上面的例子中，n=256。

#3

You can use C99 features like VLA, e.g.

你可以使用C99特性，比如VLA。

int main()
{
  int len=1234;
  struct MyStruct {int i,array[len];} var;

  var.array[0]=-1;
  var.array[len-1]=1;

  printf( "%i %i %lu", var.array[0],var.array[len-1],(unsigned long)sizeof(var) );

  return 0;
}

#1