A small question about using strtok

Today, when I got a little program, I reported an error and encountered a problem. Let's look at the code first.

int main(int argc, char* argv[]){        char *filename = "interface_ipset_1_1.json";char* split1 = "_";char* split2 = ".";char  splitfile1[4][NAME_MAX];        sagent_string_split(filename,split1,splitfile1,4);printf("1 = %s.",splitfile1[0]);        reuturn 0;}

int32_t sagent_string_split(char * str, const char * split,        char split_str[][NAME_MAX], int32_t max_num){    if (st== NULL || split == NULL || split_str == NULL || max_num <= 0)    {        printf("sagent_string_split params have error!\n");    }char* result = NULL;char* endstr = NULL;    result = strtok_r(str, split,&endstr);    int32_t i = 0;    while (result )        {        if (i >= max_num)        {            printf("split num is more than max_num = %d.", max_num);            return -1;        }        printf("i = %d,result = %s",i,result);        strncpy(split_str[i++], result, NAME_MAX - 1);        result = strtok(NULL, split);      }    return 0;}int main(int argc, char* argv[]){        char *filename = "interface_ipset_1_1.json";char* split1 = "_";char* split2 = ".";char  splitfile1[4][NAME_MAX];        sagent_string_split(filename,split1,splitfile1,4);printf("1 = %s.",splitfile1[0]);    reuturn 0;}

When executing this program, an error is reported, such as segmentation fault. Where should I step on the memory. The original char * filename = "interface_ipset_1_1.json"; this declaration is a constant and cannot be changed. strtok will modify it during use, resulting in an error. So pay attention to it. You can declare char filename [64] = "interface_ipset_00001.json"