LINUX编程-实验五 内存管理实验

实验五内存管理实验1.目的要求（1）学习使用内存管理库函数。

（2）学习分析、改正内存错误。

2.实验内容（1）内存库函数实验●malloc函数原型：extern void *malloc(unsigned int num_bytes);头文件：#include <alloc.h>功能：分配长度为num_bytes字节的内存块。

说明：如果分配成功则返回指向被分配内存的指针，否则返回空指针NULL。

当内存不再使用时，应使用free()函数将内存块释放。

举例：运行程序清单5-1，写明运行结果：_______________________________________________________________________________________________________________________________________________________________●calloc函数原型：extern void *calloc(int num_elems, int elem_size);头文件：#include <alloc.h>功能：为具有num_elems个长度为elem_size元素的数组分配内存。

说明：如果分配成功则返回指向被分配内存的指针，否则返回空指针NULL。

当内存不再使用时，应使用free()函数将内存块释放。

举例：运行程序清单5-2，写明运行结果：_______________________________________________________________________________________________________________________________________________________________●realloc函数原型：extern void *realloc(void *mem_address, unsigned int newsize);头文件：#include <alloc.h>功能：改变mem_address所指内存区域的大小为newsize长度。

说明：如果分配成功则返回指向被分配内存的指针，否则返回空指针NULL。

当内存不再使用时，应使用free()函数将内存块释放。

举例：运行程序清单5-3，写明运行结果：______________________________________________________________________ ___________________________________________________________________ ______________________（2）内存错误分析实验●分析1：指出程序清单5-4的内存错误原因。

错误原因：___ApplyForMem(char *p,int num)是不能传递动态内存的，这样main函数当中Str始终都是NULL_________________________________________________________________ ______________________________________________________________________ _____________________●分析2：指出程序清单5-5的内存错误原因。

错误原因：____(const char *)没有具体指明内存地址,这个写法表示从地址0处取一个字符,而地址0是没有东西的____________________________________________________________________ ____________________________________________________________________ ___________________●分析3：通过比较程序清单5-6、5-7输出结果，分析程序5-3内存错误原因程序5-6运行结果___________________________________________________________________ ___________________________________________________________________ _________________________程序5-7运行结果_______________________________________________________________________________________________________________________________________________________________错误原因__程序5-6释放内存的顺序和分配内存的顺序不对应。

_____________________________________________________________________________________________________________________________________________________________经验总结______堆分配内存后，释放内存的顺序应该和分配内存的逆序，这样才能保证释放内存的顺序的正确性。

________________________________________________________________________________________________________________________________________________________3.主要仪器设备及软件(1)硬件：计算机、网络(2)软件：VMWare workstation、RedHat 9.04.附录：程序清单if()(1)5-1#include <syslib.h>#include <alloc.h>main(){char *p;clrscr(); // clear screenp=(char *)malloc(100);if(p)printf("Memory Allocated at: %x",p);elseprintf("Not Enough Memory!\n");free(p);return 0;}(2)5-2#include <syslib.h>#include <alloc.h>main(){char *p;clrscr(); // clear screenp=(char *)calloc(100,sizeof(char));if(p)printf("Memory Allocated at: %x",p);elseprintf("Not Enough Memory!\n");free(p);return 0;}(3)5-3#include <syslib.h>#include <alloc.h>main(){char *p;clrscr(); // clear screenp=(char *)malloc(100);if(p)printf("Memory Allocated at: %x",p);elseprintf("Not Enough Memory!\n");p=(char *)realloc(p,256);if(p)printf("Memory Reallocated at: %x",p);elseprintf("Not Enough Memory!\n");free(p);return 0; }(4)5-4……Void ApplyForMem(char *p,int num){p=(char*)malloc(sizeof(char)*num);return;}int main(){char *str=NULL;………….ApplyForMem(str,300);free(str);infile.close();return 0;}(5)5-5#include <unistd.h>#include <stdlib.h>#include <stdio.h>int main() {char z = *(const char *)0;exit(EXIT_SUCCESS);}(6)5-6#include “stdlib.h”#define HEAP_BLOCK_SIZE 32int main(){// 分配申明heap 内存块1char *pbuf1 = (char *) malloc(HEAP_BLOCK_SIZE);printf("HeapTest block 1 (%d bytes) at %08Xh", sizeof(pbuf1), pbuf1);*pbuf1 = '1';//分配申明heap 内存块2char *pbuf2 = (char *) malloc(HEAP_BLOCK_SIZE);printf("HeapTest block 2 (%d bytes) at %08Xh", sizeof(pbuf2), pbuf2);*pbuf2 = '2';//分配申明heap 内存块 3char *pbuf3 = (char *) malloc(HEAP_BLOCK_SIZE);printf("HeapTest block 3 (%d bytes) at %08Xh", sizeof(pbuf3), pbuf3);*pbuf3 = '3';// 释放heap 内存块1printf("HeapTest block 1 (%d bytes) at %08Xh freed",sizeof(pbuf1), pbuf1);free(pbuf1);printf("HeapTest block 2 (%d bytes) at %08Xh freed",sizeof(pbuf2), pbuf2);free(pbuf2);//释放heap内存块 3printf("HeapTest block 3 (%d bytes) at %08Xh freed",sizeof(pbuf3), pbuf3);free(pbuf3);//分配申明heap 内存块4char *pbuf4 = (char *) malloc( HEAP_BLOCK_SIZE);printf("HeapTest block 4 (%d bytes) at %08Xh", sizeof(pbuf4), pbuf4);*pbuf4 = '4';//分配申明heap 内存块5char *pbuf5 = (char *) malloc( HEAP_BLOCK_SIZE);printf("HeapTest block 5 (%d bytes) at %08Xh", sizeof(pbuf5), pbuf5);*pbuf5 = '5';//分配申明heap 内存块6char *pbuf6 = (char *) malloc( HEAP_BLOCK_SIZE);printf("HeapTest block 6 (%d bytes) at %08Xh", sizeof(pbuf6), pbuf6);*pbuf6= '6';for(;;) {Sleep(1000);}return 0;}(7)5-7#include “stdlib.h”#define HEAP_BLOCK_SIZE 32int main(){// 分配申明heap 内存块1char *pbuf1 = (char *) malloc(HEAP_BLOCK_SIZE);printf("HeapTest block 1 (%d bytes) at %08Xh", sizeof(pbuf1), pbuf1);*pbuf1 = '1';//分配申明heap 内存块2char *pbuf2 = (char *) malloc(HEAP_BLOCK_SIZE);printf("HeapTest block 2 (%d bytes) at %08Xh", sizeof(pbuf2), pbuf2);*pbuf2 = '2';//分配申明heap 内存块 3char *pbuf3 = (char *) malloc(HEAP_BLOCK_SIZE);printf("HeapTest block 3 (%d bytes) at %08Xh", sizeof(pbuf3), pbuf3);*pbuf3 = '3';// 释放heap 内存块3printf("HeapTest block 3 (%d bytes) at %08Xh freed",sizeof(pbuf3), pbuf3);free(pbuf3);printf("HeapTest block 2 (%d bytes) at %08Xh freed",sizeof(pbuf2), pbuf2); free(pbuf2);//释放heap内存块 1printf("HeapTest block 1 (%d bytes) at %08Xh freed",sizeof(pbuf1), pbuf1); free(pbuf1);//分配申明heap 内存块4char *pbuf4 = (char *) malloc( HEAP_BLOCK_SIZE);printf("HeapTest block 4 (%d bytes) at %08Xh", sizeof(pbuf4), pbuf4);*pbuf4 = '4';//分配申明heap 内存块5char *pbuf5 = (char *) malloc( HEAP_BLOCK_SIZE);printf("HeapTest block 5 (%d bytes) at %08Xh", sizeof(pbuf5), pbuf5);*pbuf5 = '5';//分配申明heap 内存块6char *pbuf6 = (char *) malloc( HEAP_BLOCK_SIZE);printf("HeapTest block 6 (%d bytes) at %08Xh", sizeof(pbuf6), pbuf6);*pbuf6= '6';for(;;) {Sleep(1000);}return 0;}。