使用strsep / strdup将C字符串操纵为结构变量时出现C分段错误

Question

我又遇到了另一个分割错误（ 吟 ）。

为了到达我现在的位置，我在这里的其他问题上得到了帮助。

该功能的思想是：

• 传递一个字符*
• 将传入的char *复制到堆上并指向此位置
• 使用strsep来基于'，'分隔符分割“字符串”
• 将这些拆分标记分配给结构变量
• 释放指针

这就是我传递给函数的内容：

gga_sentence结构：

typedef struct gga_sentence{

    const char *untouched_sentence;
    gsa_sentence *gsa;
    char *sentence_id;
    int time_stamp;
    double latitude;
    char north_south_id;
    double longitude;
    char east_west_id;
    int quality;
    int no_of_satellites;
    double horizontal_dillution;
    double altitude;
    char altitude_units;
    double geodial_seperation;
    char geodial_seperation_units;
    char* age_of_data_in_seconds;
    char *checksum;

}gga_sentence;

gga_parsed是：

    gga_sentence *ggas_parsed;
    ggas_parsed = malloc(10*sizeof(gga_sentence));

其中line是一个char [100]，使用从文件中读取的行填充，这可以正常工作。

strncpy(&ggas_parsed[number_of_gga_parsed].untouched_sentence, line, strlen(line));
            printf("GGA UNTOUCHED: %s", &ggas_parsed[number_of_gga_parsed].untouched_sentence);

initiative_gga_values（＆ggas_parsed [number_of_gga_parsed]，＆ggas_parsed [number_of_gga_parsed] .untouched_sentence）;

上面的printf语句：

printf("GGA UNTOUCHED: %s", &ggas_parsed[number_of_gga_parsed].untouched_sentence);

产生：

GGA UNTOUCHED: $GPGGA,151019.000,5225.9627,N,00401.1624,W,1,09,1.0,38.9,M,51.1,M,,0000*72

所以当我通过以下方式将其传递给上述函数时：

initiate_gga_values(&ggas_parsed[number_of_gga_parsed], &ggas_parsed[number_of_gga_parsed].untouched_sentence);

函数itef定义为：

void initiate_gga_values(gga_sentence* gga_ptr, const char* sentence){

    char *temp_sentence, *second_temp_ptr;
    char *token;
    int token_no = 0;

    temp_sentence = strdup(sentence);
    second_temp_ptr = temp_sentence;

    printf("TS: %s", temp_sentence);
    printf("2nd: %s", second_temp_ptr);

    token = strsep (&second_temp_ptr,",");

    while (token != NULL) {
        /*if a sentence has missing data then make that clear by settings it's value to
         * <EMPTY>*/
        if(strlen(token)==0){
            token = "<EMPTY>";
        }
        switch(token_no){
        case 0:
            gga_ptr->sentence_id = token;
            //printf("%s,",gga_ptr->sentence_id);
            break;
        case 1:
            /*atoi converts a string to an int, well a c string anyways so a char* */
            gga_ptr->time_stamp = atoi(token);
            //printf("%d,",gga_ptr->time_stamp);
            break;
        case 2:
            /*strtod coverts a string to a double, well a c string anyways so a char* */
            gga_ptr->latitude = strtod(token, NULL);
            //printf("%f,",gga_ptr->latitude);
            break;
        case 3:
            gga_ptr->north_south_id = *token;
            //printf("%c,",gga_ptr->north_south_id);
            break;
        case 4:
            gga_ptr->longitude = strtod(token, NULL);
            //printf("%f,",gga_ptr->longitude);
            break;
        case 5:
            gga_ptr->east_west_id = *token;
            //printf("%c,",gga_ptr->east_west_id);
            break;
        case 6:
            gga_ptr->quality = atoi(token);
            //printf("%d,",gga_ptr->quality);
            break;
        case 7:
            gga_ptr->no_of_satellites = atoi(token);
            //printf("%d,",gga_ptr->no_of_satellites);
            break;
        case 8:
            gga_ptr->horizontal_dillution = strtod(token, NULL);
            //printf("%f,",gga_ptr->horizontal_dillution);
            break;
        case 9:
            gga_ptr->altitude = strtod(token, NULL);
            //printf("%f,",gga_ptr->altitude);
            break;
        case 10:
            gga_ptr->altitude_units = *token;
            //printf("%c,",gga_ptr->altitude_units);
            break;
        case 11:
            gga_ptr->geodial_seperation = strtod(token, NULL);
            //printf("%f,",gga_ptr->geodial_seperation);
            break;
        case 12:
            gga_ptr->geodial_seperation_units = *token;
            //printf("%c,",gga_ptr->geodial_seperation_units);
            break;
        case 13:
            /*This is never used in the sentenced given*/
            gga_ptr->age_of_data_in_seconds = token;
            //printf("%s,",gga_ptr->age_of_data_in_seconds);
            break;
        case 14:
            gga_ptr->checksum = token;
            //printf("%s",gga_ptr->checksum);
            break;
        }
        token_no++;
        token = strsep (&second_temp_ptr, ",");

    }

    printf("untouched: %s\n", sentence);
    printf("Second print of TS: %s\n", temp_sentence);
    printf("second print of second_temp: %s\n", second_temp_ptr);

    free(temp_sentence);
    exit(1); //DBUGGING PURPOSES
}

该函数的输出为：

TS: $GPGGA,151019.000,5225.9627,N,00401.1624,W,1,09,1.0,38.9,M,51.1,M,,0000*72
2nd: $GPGGA,151019.000,5225.9627,N,00401.1624,W,1,09,1.0,38.9,M,51.1,M,,0000*72
untouched: $GPGGA,151019.00�(m
Second print of TS: $GPGGA
second print of second_temp: (null)

因此，如果我添加此printf语句：

printf("testing untouched: %s", gga_ptr->untouched_sentence);

进入initiate_gga_values函数，就在exit（1）之前我遇到了分段错误。 使用额外的打印行再次运行代码的输出将打印出gga_ptr-> untouched_sentence，从而产生：

GGA UNTOUCHED: $GPGGA,151019.000,5225.9627,N,00401.1624,W,1,09,1.0,38.9,M,51.1,M,,0000*72
TS: $GPGGA,151019.000,5225.9627,N,00401.1624,W,1,09,1.0,38.9,M,51.1,M,,0000*72
2nd: $GPGGA,151019.000,5225.9627,N,00401.1624,W,1,09,1.0,38.9,M,51.1,M,,0000*72
untouched: $GPGGA,151019.00��b
Second print of TS: $GPGGA
second print of second_temp: (null)
Segmentation fault (core dumped)

我不知道发生了什么。

有任何想法吗？

干杯，克里斯。

Answer 1

这是错误的：

const char* untouched_sentence;

strncpy(&ggas_parsed[number_of_gga_parsed].untouched_sentence, line, strlen(line));
            printf("GGA UNTOUCHED: %s", &ggas_parsed[number_of_gga_parsed].untouched_sentence);

strncpy的第一个参数应该是将副本放入其中的缓冲区，您已为其提供了指向结构的指针。 第三个参数应该是目标缓冲区的大小，而不是输入！

您需要做：

char* untouched_sentence;

ggas_parsed[number_of_gga_parsed].untouched_sentence = malloc(<size>);

如果担心长行， <size>需要用一些限制strlen（line）。

然后：

strncpy(ggas_parsed[number_of_gga_parsed].untouched_sentence, line, strlen(line));
printf("GGA UNTOUCHED: %s",ggas_parsed[number_of_gga_parsed].untouched_sentence);

我认为您需要从一个简单的示例开始，着手进行内存管理。