Question

我在下面的fscanf行中遇到了分段错误。我添加了每个变量的字符宽度来尝试修复它，所以我不明白它为什么会出错。

我从CSV文件读取结构数组。

结构是：

typedef struct Person
    {
    int ID;
    int salary;
    int deleted;
    char salutation[4];
    char firstName[21];
    char surName[31];
    char job[16];
    } Person;

我声明了结构数组：

Person* persons;
persons = (Person*)malloc(SIZE * sizeof(Person));

然后使用while循环将CSV文件读入值：

（我初始化为0）

while(fscanf(f, "%d,%3[^,],%20[^,],%30[^,],%15[^,],%d,%d", &inPersons[i].ID, inPersons[i].salutation, inPersons[i].firstName, inPersons[i].surName, inPersons[i].job, &inPersons[i].salary, &inPersons[i].deleted)!=EOF)
            {
            newID = inPersons[i].ID;
            i++;
            }

在fscanf语句中发生了段错误。我对valgrind没有经验，但它给了我这行错误：

==16810== Invalid write of size 4
==16810==    at 0x578215: _IO_vfscanf (in /lib/libc-2.12.so)
==16810==    by 0x585368: __isoc99_fscanf (in /lib/libc-2.12.so)
==16810==    by 0x8048951: loadDb (Database.c:23)
==16810==    by 0x8048711: menu (Menu.c:37)
==16810==    by 0x804861E: main (main.c:6)
==16810==  Address 0x27230128 is not stack'd, malloc'd or (recently) free'd

我也在同一条线上得到这些Valgrind错误：

==18457== Use of uninitialised value of size 4
==18457==    at 0x405A215: _IO_vfscanf (in /lib/libc-2.12.so)
==18457==    by 0x4067368: __isoc99_fscanf (in /lib/libc-2.12.so)
==18457==    by 0x8048943: loadDb (Database.c:23)
==18457==    by 0x8048711: menu (Menu.c:37)
==18457==    by 0x804861E: main (main.c:6)


==18457== Process terminating with default action of signal 11 (SIGSEGV)
==18457==  Access not within mapped region at address 0x5C5E4128
==18457==    at 0x405A215: _IO_vfscanf (in /lib/libc-2.12.so)
==18457==    by 0x4067368: __isoc99_fscanf (in /lib/libc-2.12.so)
==18457==    by 0x8048943: loadDb (Database.c:23)
==18457==    by 0x8048711: menu (Menu.c:37)
==18457==    by 0x804861E: main (main.c:6)

Answer 1

如果你有一个字母或标点字符，你应该有一个数字，你有一个无限循环，你溢出你分配的人数组的界限。你应该检查：

while (i < SIZE && (num = fscanf(f, "...", ...)) == 7)
{
    ...process valid input...
}
...consider what to do here, using `num` to distinguish between EOF and failed conversions...

valgrind无法识别记忆的事实令人费解。您已经采取了大部分相关步骤来确保不会出现缓冲区溢出（除了正确检查fscanf()的状态之外的所有步骤）。

哦......你分配persons;你正在阅读inPersons ......这是正确的吗？

我想我会编写一个函数来调用fscanf()并检测并报告错误，然后从while循环中调用它：

while (i < SIZE && get_person(&persons[i]) != EOF)
   ...

或：

while (i < SIZE && get_person(&inPersons[i]) != EOF)
   ...

这也允许您从fscanf()切换到fgets()和sscanf()，或getline()和sscanf()。

使用fscanf时无法调试seg故障

1 个答案: