我有一个问题需要解决，但它给了我错误：
2009-EE-182-Part2.c: In function ‘main’:
2009-EE-182-Part2.c:35:13: error: expected identifier or ‘(’ before ‘->’ token
2009-EE-182-Part2.c:40:22: error: expected identifier or ‘(’ before ‘->’ token
2009-EE-182-Part2.c:41:14: error: expected identifier or ‘(’ before ‘->’ token
2009-EE-182-Part2.c:42:22: error: expected expression before ‘shared_data’
2009-EE-182-Part2.c:44:15: error: expected identifier or ‘(’ before ‘->’ token
2009-EE-182-Part2.c:54:15: error: expected expression before ‘shared_data’
2009-EE-182-Part2.c:55:19: error: expected expression before ‘shared_data’
代码是：
# include <stdio.h>
# include <sys/shm.h>
# include <sys/stat.h>
# include <sys/types.h>
# include <unistd.h>
# define MAX_SEQUENCE 10
typedef struct{
long fib_sequence[MAX_SEQUENCE];
int sequence_size;
} shared_data;
char* shared_memory; /* a pointer to the shared memory segment */
int main()
{
int a,b,m,n,i,j;
a=0; b=1;
printf("Enter the number of a Fibonacci Sequence:\n");
scanf("%d", &m);
if (m < 0)
printf("Please enter a non-negative integer\n");
else if (m> MAX_SEQUENCE)
printf("Please enter an integer less than 10\n");
int segment_id; /* the identifier for the shared memory segment */
int segment_size = sizeof(shared_data); /* the size (in bytes) of the shared memory segment */
segment_id = shmget(IPC_PRIVATE, segment_size, S_IRUSR | S_IWUSR); /** allocate a shared memory segment */
shared_data *shared_memory = shmat(segment_id, NULL, 0); /** attach the shared memory segment */
printf("\nshared memory segment %d attached at address %p\n", segment_id, shared_memory);
shared_data->sequence_size = m;
pid_t pid;
pid = fork();
if (pid == 0){
printf("Child is producing the Fibonacci Sequence...\n");
shared_data->fib_sequence[0] = a;
shared_data->fib_sequence[1] = b;
for (i=2;i<shared_data->sequence_size;i++){
n=a+b;
shared_data->fib_sequence[i] = n;
a=b;
b=n;
}
printf("\nChild ends\n");
}
else{
printf("Parent is waiting for child to complete...\n");
wait(NULL);
printf("Parent ends\n");
for(i=0;i<= shared_data->sequence_size;i++)
printf("%ld ", shared_data->fib_sequence[i]);
}
/**printf("%s \n", shared_memory); now print out the string from shared memory */
/** now detach the shared memory segment */
if ( shmdt(shared_memory) == -1) {
fprintf(stderr, "Unable to detach\n");
}
/** now remove the shared memory segment */
shmctl(segment_id, IPC_RMID, NULL);
return 0;
}
声明是 “设计斐波纳契程序的方法是在父进程和子进程之间建立共享内存段。 这种技术允许孩子将斐波那契序列的内容写入共享 - 内存段并在子项完成时让父输出序列。 由于内存是共享的，因此子进程所做的任何更改都将反映在父级中 过程也是如此。该程序将使用POSIX共享内存进行结构化，如中所述 http://graphics.im.ntu.edu.tw/~robin/courses/os07/code/03proc/shm-posix.c 该程序首先需要为共享内存段创建数据结构。使用结构最容易实现。此数据结构将包含两个项目： 1.一个固定大小的数组，其大小为MAX_SEQUENCE，用于保存Fibonacci值和 2.子进程要生成的序列的大小，即sequence_size，其中 sequence_size≤MAX_SEQUENCE。
这些项目可以在结构中表示如下：
# define MAX_SEQUENCE 10
typedef struct{
long fib_sequence[MAX_SEQUENCE];
int sequence_size;
} shared_data;
父进程将通过以下步骤进行： 一个。接受命令行上传递的参数并执行错误检查以确保 该参数≤MAX_SEQUENCE。 湾创建大小为shared_data的共享内存段。 C。将共享内存段附加到其地址空间。 d。将sequence_size的值设置为命令行上的参数。 即fork子进程并调用wait（）系统调用以等待子进程 完。 F。输出共享内存段中Fibonacci序列的值。 G。分离并删除共享内存段。
共享内存段将附加到子地址空间以及 父母的地址空间。然后子进程将Fibonacci序列写入
共享内存段。必须同步父进程和子进程，以便进行同步 在孩子完成生成之前，父母不会输出Fibonacci序列 序列。 注意：在控制台上显示足够的消息，以便用户知道某个操作的时间 例如，执行创建和终止子进程等“
专家的心意请帮助。
答案 0 :(得分：3)
第一个问题：
int a,b,m,n,i,j;
sequence.fib_sequence[0] = a;
sequence.fib_sequence[1] = b;
您永远不会初始化a和b，因此您会获得垃圾（和未定义的行为）。初始化
a = 0;
b = 1;
更深层次的问题：您设置了共享内存段，但从不使用它。您使用全局
shared_data sequence;
写入子项，并从父项中读取。由于该全局与您设置的共享内存无关，因此子进程的操作不会修改父进程sequence。
您应该使用shared_memory，指向共享内存的指针来写入和读取。因此，而不是char*，它应该是
shared_data *shared_memory = shmat(...);
然后使用shared_memory->sequence[i]等。
修复shared_data/shared_memory混合并添加一些错误检查后，程序可能看起来像
# include <stdlib.h>
# include <stdio.h>
# include <sys/shm.h>
# include <sys/stat.h>
# include <sys/types.h>
# include <unistd.h>
# include <sys/wait.h>
# include <errno.h>
// So we could use other sizes without editing the source.
#ifndef MAX_SEQUENCE
# define MAX_SEQUENCE 10
#endif
// Check that MAX_SEQUENCE is large enough!
#if MAX_SEQUENCE < 2
#error MAX_SEQUENCE must be at least 2
#endif
typedef struct{
long fib_sequence[MAX_SEQUENCE];
int sequence_size;
} shared_data;
int main()
{
int a, b, m, n, i;
a = 0; b = 1;
printf("Enter the number of a Fibonacci Sequence:\n");
// Always check whether input conversion worked
if (scanf("%d", &m) != 1) {
printf("Invalid input, couldn't be converted.\n");
return EXIT_FAILURE;
}
if (m <= 0) {
printf("Please enter a positive integer\n");
return EXIT_FAILURE; // exit if input is invalid
} else if (m > MAX_SEQUENCE) {
printf("Please enter an integer less than %d\n", MAX_SEQUENCE);
return EXIT_FAILURE; // exit if input is invalid
}
/* the identifier for the shared memory segment */
int segment_id;
/* the size (in bytes) of the shared memory segment */
size_t segment_size = sizeof(shared_data);
/* allocate a shared memory segment */
segment_id = shmget(IPC_PRIVATE, segment_size, S_IRUSR | S_IWUSR);
// Check result of shmget
if (segment_id == -1) {
perror("shmget failed");
return EXIT_FAILURE;
}
/* attach the shared memory segment */
shared_data *shared_memory = shmat(segment_id, NULL, 0);
// Check whether attaching succeeded
if ((void*)shared_memory == (void*)-1) {
perror("shmat failed");
goto destroy; // clean up
}
printf("\nshared memory segment %d attached at address %p\n", segment_id, (void*)shared_memory);
shared_memory->sequence_size = m;
pid_t pid;
pid = fork();
if (pid == 0){
printf("Child is producing the Fibonacci Sequence...\n");
shared_memory->fib_sequence[0] = a;
shared_memory->fib_sequence[1] = b;
for (i = 2; i < shared_memory->sequence_size; i++){
n = a+b;
shared_memory->fib_sequence[i] = n;
a = b;
b = n;
}
printf("\nChild ends\n");
}
else{
printf("Parent is waiting for child to complete...\n");
wait(NULL);
printf("Parent ends\n");
for(i = 0; i < shared_memory->sequence_size; i++) {
printf("%ld ", shared_memory->fib_sequence[i]);
}
printf("\n");
}
/* now detach the shared memory segment */
if (shmdt(shared_memory) == -1) {
fprintf(stderr, "Unable to detach\n");
}
destroy:
/* now remove the shared memory segment */
shmctl(segment_id, IPC_RMID, NULL);
return 0;
}