操作系统 ----- 段错误（核心转储）

今天在linux下面编码程序的时候，出现了个错误   “已放弃（核心已转储）”，此前碰到过几次“段错误（核心已转储）”，做下笔记。

段错误（核心已转储）：通常是内存越界造成的，可以检查是否使用了NULL的指针，或者数组越界。调试收到的信号是SIGSEGV。

已放弃（核心已转储）：我碰到的这次是因为试图用free()函数释放一个全局变量。free只能释放用户申请在堆里的内存，用malloc()函数申请的内存就是在堆里面的，这些内存才能用free释放。使用的时候调用层次多了可能忘了这是一个全局变量。

附主程序代码：

  1 /*主程序main（）（文件名main.c）*/
  2 
  3 #include <string.h>
  4 #include <stdio.h>
  5 #include <arpa/inet.h>
  6 #include "filesys.h"
  7 #include <malloc.h>
  8 #include<string.h>
  9 struct hinode hinode[NHINO];
 10 struct dir dir;
 11 struct file sys_ofile[SYSOPENFILE];
 12 struct filsys filsys;
 13 struct pwd pwd[PWDNUM];
 14 struct user user[USERNUM];
 15 FILE * fd;
 16 struct inode * cur_path_inode;
 17 int user_id,file_block;
 18 
 19 main()
 20 {
 21 unsigned short ab_fd1,ab_fd2,ab_fd3,ab_fd4;
 22 unsigned short bhy_fd1;
 23 char * buf;
 24 printf("\nDo you want to format the disk?\n");
 25 if(getchar()=='y')
 26 {
 27 printf("Format will erase all context on the disk.Are you sure?\n");
 28 getchar();
 29 }
 30 else
 31 return;
 32 if(getchar()=='y')
 33 format();
 34 else
 35 return;
 36 install();
 37 _dir();
 38 login(2118,"abcd");
 39 user_id=0;
 40 mkdir("a2118");
 41 chdir("a2118");
 42 ab_fd1=create(user_id,"file0.c",01777);
 43 file_block=BLOCKSIZ * 6+5;
 44 buf=(char *)malloc(BLOCKSIZ * 6+5);
 45 write(ab_fd1,buf,BLOCKSIZ * 6+5);
 46 close(user_id,ab_fd1);
 47 free(buf);
 48 //delete []buf;
 49 
 50 
 51 mkdir("subdir");
 52 chdir("subdir");
 53 ab_fd2=create(user_id,"file1.c",01777);
 54 file_block=BLOCKSIZ * 4+10;
 55 buf=(char*)malloc(BLOCKSIZ*4+20);
 56 write(ab_fd2,buf,BLOCKSIZ*4+20);
 57 close(user_id,ab_fd2);
 58 buf=NULL;
 59 free(buf);
 60 //delete []buf;
 61 
 62 
 63 chdir("..");
 64 ab_fd3=create(user_id,"file2.c",01777);
 65 file_block=BLOCKSIZ * 3+255;
 66 buf=(char*)malloc(BLOCKSIZ*3+255);
 67 write(ab_fd3,buf,BLOCKSIZ*3+255);
 68 close(user_id,ab_fd3);
 69 buf=NULL;
 70 free(buf);
 71 //delete []buf;
 72 
 73 _dir();
 74 delete("ab_file0.c");
 75 
 76 ab_fd4=create(user_id,"file3.c",01777);
 77 file_block=BLOCKSIZ * 8+300;
 78 buf=(char*)malloc(BLOCKSIZ * 8+300);
 79 write(ab_fd4,buf,BLOCKSIZ * 8+300);
 80 close(user_id,ab_fd4);
 81 buf=NULL;
 82 free(buf);
 83 //delete []buf;
 84 
 85 
 86 _dir();
 87 ab_fd3=open(user_id,"file2.c",FAPPEND);
 88 file_block=BLOCKSIZ * 3+100;
 89 buf=(char*)malloc(BLOCKSIZ * 3+100);
 90 write(ab_fd3,buf,BLOCKSIZ * 3+100);
 91 close(user_id,ab_fd3);
 92 buf=NULL;
 93 free(buf);
 94 //delete []buf;
 95 
 96 _dir();
 97 chdir("..");
 98 logout();
 99 halt();
100 }

 

 

在main函数中我加入了一些信息便于发现内存泄漏的所在，通过执行看结果，发现是format（）方法出现了错误

 

附上format()方法：

  1 ormat()
  2 {
  3 struct inode *inode;
  4 struct direct dir_buf[BLOCKSIZ/(DIRSIZ+2)];
  5 struct filsys;
  6 unsigned int block_buf[BLOCKSIZ/sizeof(int)];
  7 char *buf;
  8 int i,j;
  9 
 10 fd=fopen("filesystem","r+w+b");
 11 buf=(char* )malloc((DINODEBLK+FILEBLK+2)*BLOCKSIZ*sizeof(char));
 12 if(buf==NULL)
 13 {
 14 printf("\nfile system file create failed!\n");
 15 exit(0);
 16 }
 17 fseek(fd,0,SEEK_SET);
 18 fwrite(buf,1,(DINODEBLK+FILEBLK+2)*BLOCKSIZ*sizeof(char),fd);
 19 
 20 pwd[0].p_uid=2116;
 21 pwd[0].p_gid=03;
 22 strcpy(pwd[0].password,"dddd");
 23 pwd[1].p_uid=2117;
 24 pwd[1].p_gid=03;
 25 strcpy(pwd[1].password,"bbbb");
 26 pwd[2].p_uid=2118;
 27 pwd[2].p_gid=04;
 28 strcpy(pwd[2].password,"abcd");
 29 pwd[3].p_uid=2119;
 30 pwd[3].p_gid=04;
 31 strcpy(pwd[3].password,"cccc");
 32 pwd[4].p_uid=2220;
 33 pwd[4].p_gid=05;
 34 strcpy(pwd[4].password,"eeee");
 35 
 36 
 37 inode=iget(0);
 38 inode->di_mode=DIEMPTY;
 39 iput(inode);
 40 inode=iget(1);
 41 inode->di_number=1;
 42 inode->di_mode=DEFAULTMODE|DIDIR;
 43 inode->di_size=3*(DIRSIZ+2);
 44 inode->di_addr[0]=0;
 45 strcpy(dir_buf[0].d_name,"..");
 46 dir_buf[0].d_ino=1;
 47 strcpy(dir_buf[1].d_name,".");
 48 dir_buf[1].d_ino=1;
 49 strcpy(dir_buf[2].d_name,"etc");
 50 dir_buf[2].d_ino=2;
 51 fseek(fd,DATASTART,SEEK_SET);
 52 fwrite(dir_buf,1,3*(DIRSIZ+2),fd);
 53 iput(inode);
 54 
 55 inode=iget(2);
 56 inode->di_number=1;
 57 inode->di_mode=DEFAULTMODE|DIDIR;
 58 inode->di_size=3*(DIRSIZ+2);
 59 inode->di_addr[0]=1;
 60 strcpy(dir_buf[0].d_name,"..");
 61 dir_buf[0].d_ino=1;
 62 strcpy(dir_buf[1].d_name,".");
 63 dir_buf[1].d_ino=2;
 64 strcpy(dir_buf[2].d_name,"password");
 65 dir_buf[2].d_ino=3;
 66 fseek(fd,DATASTART+BLOCKSIZ*1,SEEK_SET);
 67 fwrite(dir_buf,1,3*(DIRSIZ+2),fd);
 68 iput(inode);
 69 
 70 
 71 inode=iget(3);
 72 inode->di_number=1;
 73 inode->di_mode=DEFAULTMODE|DIDIR;
 74 inode->di_size=BLOCKSIZ;
 75 inode->di_addr[0]=2;
 76 for(i=5;i<PWDNUM;i++)
 77 {
 78 pwd[i].p_uid=0;
 79 pwd[i].p_gid=0;
 80 
 81 
 82 strcpy(pwd[i].password,"    ");
 83 }
 84 fseek(fd,DATASTART+2*BLOCKSIZ,SEEK_SET);
 85 fwrite(pwd,1,BLOCKSIZ,fd);
 86 iput(inode);
 87 
 88 filsys.s_isize=DINODEBLK;
 89 filsys.s_fsize=FILEBLK;
 90 filsys.s_ninode=DINODEBLK*BLOCKSIZ/DINODESIZ-4;
 91 filsys.s_nfree=FILEBLK-3;
 92 for(i=0;i<NICINOD;i++)
 93 {
 94 filsys.s_inode[i]=4+i;
 95 }
 96 
 97 filsys.s_pinode=0;
 98 filsys.s_rinode=NICINOD+4;
 99 
100 block_buf[NICFREE-1]=FILEBLK+1;
101 for(i=0;i<NICFREE-1;i++)
102 block_buf[NICFREE-2-i]=FILEBLK-i;
103 fseek(fd,DATASTART+BLOCKSIZ*(FILEBLK-NICFREE-1),SEEK_SET);
104 fwrite(block_buf,1,BLOCKSIZ,fd);
105 for(i=FILEBLK-NICFREE-1;i>2;i-=NICFREE)
106 {
107 for(j=0;j<NICFREE;j++)
108 {
109 block_buf[j]=i-j;
110 }
111 block_buf[j]=50;
112 fseek(fd,DATASTART+BLOCKSIZ*(i-1),SEEK_SET);
113 fwrite(block_buf,1,BLOCKSIZ,fd);
114 }
115 j=i+NICFREE;
116 for(i=j;i>2;i--)
117 {
118 filsys.s_free[NICFREE-1+i-j]=i;
119 }
120 filsys.s_pfree=NICFREE-1-j+3;
121 filsys.s_pinode=0;
122 fseek(fd,BLOCKSIZ,SEEK_SET);
123 fwrite(&filsys,1,sizeof(filsys),fd);
124 fseek(fd,BLOCKSIZ,SEEK_SET);
125 fread(&filsys.s_isize,1,sizeof(filsys),fd);
126 }

 

posted @ 2016-06-26 21:14  #ifndef  阅读(5067)  评论(1)  编辑  收藏  举报