我对 C 相当缺乏经验,并且遇到了我无法理解原因的“总线错误”。我从未听说过 gdb,但在这个论坛上遇到了它,并尝试在我的问题程序中使用它并得到以下输出:
% gdb Proc1 GNU gdb 5.0
...
此 GDB 配置为“sparc-sun-solaris2.8”...
(未找到调试符号)...
(gdb) 运行
启动程序:/home/0/vlcek/CSE660/Lab3/Proc1
(未找到调试符号)...
(未找到调试符号)...
(未找到调试符号)...
程序收到信号 SIGSEGV,分段错误。main() 中的 0x10a64
我不知道这意味着什么,是说我的代码中的第 10 行有错误吗?如果是这样,我的代码中的第 10 行只是“int main()”,所以我不确定那里的问题......当我尝试运行程序时,它所说的只是“总线错误”,所以我不确定在哪里从这里走。我什至尝试在 main 之后放置一个 printf 并且它不打印字符串,只会给我一个总线错误。
下面是我的代码:
// Compilation Command: gcc -o Proc1 Proc1.c ssem.o sshm.o
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include "ssem.h"
#include "sshm.h"
// Code of Proc1
int main()
{int i, internal_reg;
int key1 = 111111, key2 = 222222, key3 = 333333, key4 = 444444;
/* here create and initialize all semaphores */
int sem1 = sem_create(key1, 1);
if (sem1 < 0) {
perror("sem failed");
}
int sem2 = sem_create(key2, 1);
if (sem2 < 0) {
perror("sem failed");
}
int sem3 = sem_create(key3, 1);
if (sem3 < 0) {
perror("sem failed");
}
int sem4 = sem_create(key4, 1);
if (sem4 < 0) {
perror("sem failed");
}
/* here created: shared memory array Account of size 3 */
int *Account;
int shmid = shm_get(123456, (void**) &Account, 3*sizeof(int));
if (shmid < 0) {
perror("shm failed");
}
Account[0]=10000;
Account[1]=10000;
Account[2]=10000;
/* synchronize with Proc2, Proc3 and Proc4 (4 process 4 way synchronization)*/
for (i = 0; i < 1000; i++)
{
sem_signal(sem1);
sem_signal(sem1);
sem_signal(sem1);
internal_reg = Account[0];
internal_reg = internal_reg - 200;
Account[0] = internal_reg;
/* same thing, except we're adding $100 to Account1 now... */
internal_reg = Account[1];
internal_reg = internal_reg + 200;
Account[1] = internal_reg;
if (i % 100 == 0 && i != 0) {
printf("Account 0: $%i\n", Account[0]);
printf("Account 1: $%i\n", Account[1]);
}
if (i == 300 || i == 600) {
sleep(1);
}
sem_wait(sem2);
sem_wait(sem3);
sem_wait(sem4);
}
/* Here add a code that prints contents of each account
and their sum after 100th, 200th, 300th, ...., and 1000th iterations*/
}
/*in the code above include some wait and signal operations on semaphores. Do no
t over-synchronize. */
这是 ssem 和 sshm 的文档:
/*
* ssem.c
*
* Version 1.0.0
* Date : 10 Jan 2002
*
*/
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/types.h>
#include "ssem.h"
#define PERMS 0600
static struct sembuf op_lock[1] = {
0, -1, 0
};
static struct sembuf op_unlock[1] = {
0, 1, IPC_NOWAIT
};
int sem_create(int key,int initval)
{
int semid,i;
semid = semget((key_t)key, 1, IPC_CREAT | PERMS);
for(i=0;i<initval;i++)
semop(semid,&op_unlock[0],1);
return semid;
}
int sem_open(int key)
{
int semid;
semid = semget(key,0,0);
return semid;
}
int sem_wait(int semid)
{
return semop(semid,&op_lock[0],1);
}
int sem_signal(int semid)
{
return semop(semid,&op_unlock[0],1);
}
int sem_rm(int semid)
{
return semctl(semid, 0, IPC_RMID, 0);
}
/*
* sshm.c
*
* Routines for Simpler shared memory operations
* Version : 1.0.0.
* Date : 10 Jan 2002
*
*/
#include <sys/shm.h>
#include <sys/ipc.h>
#include <sys/types.h>
#include "sshm.h"
#define PERMS 0600
int shm_get(int key, void **start_ptr, int size)
{
int shmid;
shmid = shmget((key_t) key, size, PERMS | IPC_CREAT);
(*start_ptr) = (void *) shmat(shmid, (char *) 0, 0);
return shmid;
}
int shm_rm(int shmid)
{
return shmctl(shmid, IPC_RMID, (struct shmid_ds *) 0);
}
在使用 -ggdb 标志编译 Proc1.c 并运行 gdb 后,我得到以下信息:
程序收到信号 SIGSEGV,分段错误。0x10a64 in main () at Proc1.c:36
36 帐户[0]=10000
为什么这会导致分段错误?
将 Account 的声明更改为
int *Account = 0;
并添加
printf("Account == %p\n", Account);
在帐户 [0] = 10000 之前;
我在运行 Proc1 时得到以下信息:
Account == ffffffff
Bus error