2.3、预备知识-动态内存的分配和释放

大多数值得做的事情都不简单~

动态内存的分配和释放

打个例子：

#include <stdio.h>
#include <malloc.h>
int main(void)
{
    
	int a[5] = {
    10, 22, 2021, 2001, 2020};
	int len;
	printf("请输入需要分配的数组的长度：len = ");
	scanf("%d",&len);
	
	int * pArr = (int *)malloc(sizeof(int) * len);
	
	int i;
	// 可以将pArr当作一个普通数组来使用 
	for(i = 0; i < len; i++)
	{
    
		scanf("%d",&pArr[i]);
	}
	
	for(i = 0; i < len; i++)
	{
    
		printf("%d\t",*(pArr+i));
		//等价于 printf("%d\t",pArr[i]);
	}
	free(pArr); //将pArr所代表的动态分配的4*len个字节的内存释放 
	return 0;
}

跨函数使用内存

#include<stdio.h>
#include<malloc.h>
struct Student
{
    
	int sid;
	int age;
};

// 函数申明
struct Student * CreateStudent(void);
void ShowStudent(struct Student * ps);

int main(void)
{
    
	struct Student * ps;
	
	ps = CreateStudent();
	ShowStudent(ps);
	return 0;	
} 

struct Student * CreateStudent(void)
{
    
	struct Student * p = (struct Student *)malloc(sizeof(struct Student));
	p->sid = 1001;
	p->age = 21;
	return p;
}

void ShowStudent(struct Student * pst)
{
    
	printf("%d %d\n", pst->sid,pst->age);
}