C程序分段故障主（）

时间：2015-04-08 22:08:37

标签： c segmentation-fault argv argc

我是C编程的新手，我已经编写了一个代码来满足需求规范，但是我一直在收到Segmentation Fault而无法继续。 如果文件名是＆＃39; code.c＆＃39;并且它运行时没有传递参数（filename）的错误。但是如果文件名被传递，我们将进入Segmentation Fault。 任何帮助/建议将不胜感激。

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>



struct _data 
{               
   char *firstName;
   char *lastName;
   long number;
}; 

// SCAN FILE
int SCAN(FILE *(*stream))
{
    *stream = fopen("inputFile.data", "r");

    int ch = 0, lines = 0;

    while (!feof(*stream))
    {
        ch = fgetc(*stream);
        if (ch == '\n')
        {
            lines++;
        }
    }
    return lines;
}

// LOAD FILE
struct _data *LOAD(FILE *stream, int size) 
{
    int i;
    size_t chrCount;
    char *text, *number, *firstName, *lastName;
    struct _data *BlackBox;

    if ((BlackBox = (struct _data*)calloc(size, sizeof(struct _data))) == NULL) 
    {
          printf("ERROR - Could not allocate memory.\n");
          exit(0);
    }

    rewind(stream);


    for (i = 0; i < size; i++) 
    {
        getline(&text, &chrCount, stream);
        firstName   = strtok(text, " ");
        lastName    = strtok(text, " ");
        number      = strtok(NULL, "\n");

        // Allocate memory for name part of struct.
        if ((BlackBox[i].firstName = (char*)calloc(strlen(firstName), sizeof(char))) == NULL) 
        {
           printf("ERROR - Could not allocate memory.\n");
           exit(0);
        }
        if ((BlackBox[i].lastName = (char*)calloc(strlen(lastName), sizeof(char))) == NULL)
        {
           printf("ERROR - Could not allocate memory.\n");
           exit(0);
        }

        strcpy(BlackBox[i].firstName, firstName);
        strcpy(BlackBox[i].lastName, lastName);
        BlackBox[i].number = atol(number);
    }
    fclose(stream);
    return BlackBox;
}


void SEARCH(struct _data *BlackBox, char *name, int size, int inputs) 
{
    int i;
    int found = 0;
    char *search = " ";
    char *firstName;
    char *lastName; 

    if (inputs == 2)
    {
        firstName = strtok(name, search);
        lastName = strtok(NULL, search);
    }


    printf("*******************************************\n");
    if (inputs == 2)
    {   
        for (i = 0; i < size; i++) 
        {          
            if (!strcasecmp(firstName, BlackBox[i].firstName) && !strcasecmp(firstName, BlackBox[i].firstName))
            {
                printf("The name was found at the %d entry.\n", i);
                found = 1;
                break;
            }
        }
    }
    else
    {
        for (i = 0; i < size; i++) 
        {          
            if (!strcasecmp(firstName, BlackBox[i].firstName) || !strcasecmp(firstName, BlackBox[i].firstName))
            {
                printf("The name was found at the %d entry.\n", i);
                found = 1;
                break;
            }
        }
    }

    if (found == 0) 
    {
          printf("The name was NOT found.\n");
    }
    printf("*******************************************\n");
}

// FREE MEMORY
void FREE(struct _data *BlackBox, int size) 
{
    int i;
    for (i = 0; i < size; i++) 
    {
        free(BlackBox[i].firstName);
        free(BlackBox[i].lastName);
    } 
    free(BlackBox);
    BlackBox = NULL;
}


// MAIN
int main(int argv, char **argc) 
{
    int size;
    FILE *stream;
    struct _data *BlackBox;

    // argv == 1 WORKS, Below message is printed.
    if (argv == 1) 
    {          
        printf("*******************************************\n");
        printf("* You must include a name to search for.  *\n");
        printf("*******************************************\n");
    }
    // argv == 2 DOES NOT WORK, Segmentation Fault.     
    if (argv == 2) 
    {
        size = SCAN (&stream);
        BlackBox = LOAD(stream, size);
        SEARCH(BlackBox, argc[1], size, 1);
    }
    if (argv == 3) 
    {
        size = SCAN(&stream);
        BlackBox = LOAD(stream, size);
        SEARCH(BlackBox, argc[2], size, 2);
    }
    return 0;
}

3 个答案:

答案 0 :(得分：0)

您在此代码中遇到问题：

    firstName   = strtok(text, " ");
    lastName    = strtok(text, " ");
    number      = strtok(NULL, "\n");

... 

    BlackBox[i].number = atol(number);

第二个strtok()调用应该将NULL作为其第一个参数传递。实际上，第三个strtok()调用是某些以返回NULL，因为第一个调用会修改text，使第二个调用消耗整个事物（当从一开始就再次进行标记时，就像它错误地那样）。但是，您没有对此进行测试，因此atol()尝试取消引用空指针。

<强>更新：

此外，正如@chqrlie和后来的@JamesWilkins所观察到的那样，您没有为BlackBox[i].firstName和BlackBox[i].lastName分配足够的空间，因为您还需要为字符串终结符留出空间。这是一个完全独立的问题，可能也产生段错误。我喜欢@ chqrlie关于切换到strdup()的建议，但只需将每个分配增加一个单位就足够了。

更新2 ：

此外，您对此行有疑问：

    getline(&text, &chrCount, stream);

在第一次调用之前，您不会初始化变量text，因此它包含垃圾值。该函数仅在其第一个参数指向NULL指针时才分配缓冲区;否则它将该行写入由解除引用第一个参数获得的指针所指向的缓冲区。写入内存中的随机位置肯定会产生未定义的行为，实际上这通常表现为段错误。

此外，除非您可以依赖文件的行不长于第一行，否则还需要在每次循环迭代结束时释放text指针并将其值重置为NULL ，以便getline()在下一次迭代中分配一个新的缓冲区。如果你没有在每次迭代时释放它，那么你需要在循环结束后释放它;否则你会泄漏记忆。

答案 1 :(得分：0)

试试这个（虽然我在Windows上使用Visual Studio）。我添加了代码以检查最后一行中是否缺少'\ n'，并且还允许可变数量的搜索项。我还将字符串的内存分配增加了1，以便考虑空终止字符。我注意到你正在使用getline(const char*...，我认为它是GNU（Linux？），所以我将其更改为fgets()，这样我就可以在VS中编译和测试它（所以你可以改回来，如果你喜欢）。我也进行了各种空检查，以便更安全。

#include <iostream>

using namespace std;

struct _data
{
    char *firstName;
    char *lastName;
    long number;
};

// SCAN FILE
int SCAN(FILE *(*stream))
{
    *stream = fopen("inputFile.data", "r");
    if (*stream == NULL)
    {
        perror("Error opening file");
        return 0;
    }

    char ch = 0, lines = 0, linesize = 0;

    while ((ch = fgetc(*stream)) != EOF)
    {
        if (ch == '\n')
        {
            lines++;
            linesize = 0;
        }
        else linesize++;
    }

    if (linesize > 0)
        lines++; // (last line doesn't have '\n')

    return lines;
}

// LOAD FILE
struct _data *LOAD(FILE *stream, int lineCount)
{
    int i;
    size_t chrCount = 256;
    char text[256], *result, *number, *firstName, *lastName;
    struct _data *BlackBox;

    if ((BlackBox = (struct _data*)calloc(lineCount, sizeof(struct _data))) == NULL)
    {
        printf("ERROR - Could not allocate memory.\n");
        exit(0);
    }
    else memset(BlackBox, 0, sizeof(struct _data) * lineCount); // (make sure all data members are null to begin)

    rewind(stream);


    for (i = 0; i < lineCount; i++)
    {
        result = fgets(text, chrCount, stream);
        if (result == NULL)
            break; // (EOF)

        firstName = strtok(text, " ");
        lastName = strtok(NULL, " ");
        number = strtok(NULL, "\n");

        // Allocate memory for name part of struct.
        if ((BlackBox[i].firstName = (char*)calloc(strlen(firstName) + 1, sizeof(char))) == NULL)
        {
            printf("ERROR - Could not allocate memory.\n");
            exit(0);
        }
        if ((BlackBox[i].lastName = (char*)calloc(strlen(lastName) + 1, sizeof(char))) == NULL)
        {
            printf("ERROR - Could not allocate memory.\n");
            exit(0);
        }

        strcpy(BlackBox[i].firstName, firstName);
        strcpy(BlackBox[i].lastName, lastName);
        BlackBox[i].number = atol(number);
    }

    fclose(stream);

    return BlackBox;
}


void SEARCH(struct _data *BlackBox, char **names, int lineCount, int inputs)
{
    int i, l;
    int found = 0;

    printf("*******************************************\n");

    for (i = 0; i < inputs; ++i)
    {
        for (l = 0; l < lineCount; ++l)
        {
            if (BlackBox[l].firstName != NULL && !_stricmp(names[i], BlackBox[l].firstName)
                || BlackBox[l].lastName != NULL && !_stricmp(names[i], BlackBox[l].lastName))
            {
                printf("The name was found on line %d.\n", 1 + l);
                found = 1;
                break;
            }
        }
        if (found) break;
    }

    if (!found)
        printf("The name was NOT found.\n");

    printf("*******************************************\n");
}

// FREE MEMORY
void FREE(struct _data *BlackBox, int lineCount)
{
    int i;
    for (i = 0; i < lineCount; i++)
    {
        if (BlackBox[i].firstName != NULL)
            free(BlackBox[i].firstName);
        if (BlackBox[i].lastName != NULL)
            free(BlackBox[i].lastName);
    }
    free(BlackBox);
}


// MAIN
int main(int argc, char **argv)
{
    int lineCount;
    FILE *stream;
    struct _data *BlackBox;

    // argc == 1 WORKS, Below message is printed.
    if (argc == 1)
    {
        printf("*******************************************\n");
        printf("* You must include a name to search for.  *\n");
        printf("*******************************************\n");
    }
    // argc == 2 DOES NOT WORK, Segmentation Fault.     
    if (argc > 1)
    {
        lineCount = SCAN(&stream);
        if (lineCount > 0)
        {
            BlackBox = LOAD(stream, lineCount);
            SEARCH(BlackBox, argv + 1, lineCount, argc - 1);
            FREE(BlackBox, lineCount);
        }
    }
    return 0;
}

在命令行上测试它，它可以工作。

答案 2 :(得分：-2)

问题在于argv和argc。 argc应该是一个int（思考参数 count ），而argv应该是char**。你将它们混合在main。

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