C语言 柔性数组的使用详解

struct S
{
	int x;
	int a[];
};
int main()
{
	printf("%d", sizeof(S));
}

#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<stdlib.h>
 
struct S
{
	int x;
	int a[];
};
int main()
{
    //为柔性数组a[]开辟了40个字节的空间
	struct S *ps =(struct S*)malloc(sizeof(struct S) + 40);
	if (ps == NULL)                                    //检查是否为空指针
	{
		perror("ps");
		return 1;
	}
	ps->x = 10;												
	int i = 0;					
	for (i = 0; i < 10; i++)								
	{                                                  
		ps->a[i] = i;                                   //数组使用
	}
	for (i = 0; i < 10; i++)
	{
		printf("%d  ",ps->a[i]);                        //数组打印
	}
	//若觉得40不够用，可用realloc扩容
	//如:
	struct S* ptr = (struct S*)realloc(ps, sizeof(struct S) + 80);
	if (ptr == NULL)                                    //检查是否为空指针
	{
		perror("realloc");
		return 1;
	}
	else
	{
		ps = ptr;
	}
 
	free(ps);                                            //释放内存并置为空指针
	ps = NULL;
}

#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<stdlib.h>
 
struct S
{
	int x;
	int *a;
};
int main()
{
	struct S* ps = (struct S*)malloc(sizeof(struct S) );//为结构体变量x开辟空间
	if (ps == NULL)
	{
		return 1;
	}
	ps->a = (int*)malloc(40);							//为字符串指针开辟40个字节的空间
	if (ps->a == NULL)
	{
		free(ps);
		ps = NULL;
		return 1;
	}
	free(ps->a);
	ps->a = NULL;
 
	free(ps);
	ps = NULL;
}