[英]C Passing char array to function using structs
我们有一个小程序,其中输入来自文本文件(请参阅下面的文本示例),用于扫描某些学生信息并将其写入不同的结构变量。 然而,当add_student()函数被调用时,它给出了这个奇怪的输出(见下面的截图)。
struct student_list sl;
struct teacher_list tl;
struct data {
char *name;
int number;
char index;};
struct student {
struct data *d;
struct student *next;};
struct student_list{
int size;
struct student *front;
struct student *tail;};
struct teacher{
struct data *d;
struct teacher *next;};
struct teacher_list{
int size;
struct teacher *front;
struct teacher *tail;};
void main()
{
readAndLoad();
print_students();
}
void readAndLoad()
{
int c;
int i=0;
char line[200];
int number, semNum;
char name[100];
char index;
while ((c=getchar())!=EOF)
{
if(c != '\n')
{
line[i++] = c;
line[i] = '\0';
/*printf("%c ", c);
printf("%s \n", line);*/
}else
{
//printf("\n");
int j, b;
b = 0;
for (j = 0; j < sizeof(line); j++)
{
if (line[j] == ' ')
++b;
}
//printf("%s \n", line);
if (b == 2)
{
if (line[0] == 'S')
{
sscanf(line, "S %d %s", &number, name);
struct student *studentnode;
studentnode = malloc(sizeof(struct student));
add_student(&studentnode, number, &name);
} else if (line[0] == 'T')
{
sscanf(line, "T %d %s", &number, name);
struct teacher *teachernode;
teachernode = malloc(sizeof(struct teacher));
add_teacher(&teachernode, number, &name);
}
}
memset(&line[0], 0, sizeof(line));
i=0;
}
}
//printf(line);
}
void add_student(struct student *n, int student_number, char *student_name)
{
//---------------------------------------------------
printf("%s\n", student_name);
n->d->name = student_name;
n->d->number = student_number;
n->d->index = 'S';
n->next = 0;
printf("%s\n", n->d->name);
//---------------------------------------------------
if (sl.size == 0)
{
sl.front = n;
sl.tail = n;
printf("%s %d \n", n->d->name, n->d->number);
} else
{
sl.tail->next = n;
sl.tail = n;
printf("%s %d \n", n->d->name, n->d->number);
}
sl.size++;
printf("Student added\n");
}
void add_teacher(struct teacher *n, int number, char *name)
{
n->d->name = name;
n->d->number = number;
n->d->index = 'T';
n->next = 0;
if (tl.size == 0)
{
tl.front = n;
tl.tail = n;
} else
{
tl.tail->next = n;
tl.tail = n;
}
tl.size++;
printf("Teacher added\n");
}
void print_students()
{
int i;
struct student *s = sl.front;
for (i = 0; i < sl.size; i++)
//while (s->next != 0)
{
if (i == (sl.size - 2))
{
printf("%c %s %d", s->d->index, s->d->name, s->d->number);
} else
{
printf("%c %s %d \n", s->d->index, s->d->name, s->d->number);
s = s->next;
}
}
}
在代码中突出显示的部分 //------------------- 之间,我们可以看到第一个 printf() 的名称的正确输出,但是当我们转到第二个时printf() 它只打印空格...你知道可能是什么问题吗?
输入文本文件:
S 123456 Ivan
S 654321 Georgi
T 123456 Jesper
T 123457 Ole
T 123458 Lars
T 123459 Erland
C 31 CALI1 3
C 11 WDDI1 1
C 21 SDJI2 2
E 123456 31
E 123456 11
E 654321 21
A 123456 31
A 123457 11
控制台输出:
Ivan
123456
Student added
Georgi
,▒( 654321
Student added
Teacher added
Teacher added
Teacher added
Teacher added
E 0▒( 2673448E 0▒( 2673448
studentnode = malloc(sizeof(struct student));
只为student
实例分配内存。 studentnode->d
的内存尚未分配。 因此, add_student()
任何n->d->something
都是无效的,从而调用未定义的行为。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.