分段错误 - 拆分字符串

Question

Can you please help me with fixing below code. Not sure where the segmentation fault is.

 char str[] = "00ab00,00cd00";
 char **strptr;
 int i;

 strptr = malloc(sizeof(char*) * 2);

 strcnt = 0;
 int j=0;
 for(i=0;i<sizeof(str);i++) {

   char c = *(str+i);
   printf("%c", c);

   if(c==',') {
     strcnt++;
     j=0;
   }

   strptr[strcnt][j++] = c;

 }

Please ignore my poor coding :)

PS: I know its possible to split using strtok() easily.

Answer 1

Not sure where the segmentation fault is

As others have mentioned in the comments, you are not assigning memory to the pointers strptr[0] and strptr[1] but, you are trying to access them. This leads to segmentation fault.

Use a for loop to initially assign memory to strptr[0] and strptr[1]

strptr = malloc(sizeof(char*) * 2);
for(i = 0; i < 2; i++) //here, initialise each to 1 byte
{
    strptr[i] = malloc(1); 
}
strcnt = 0;

Here's a question on how to initialise a pointer to a pointer .

---

then, resize them at each step as you add additional character using the realloc() function.

for(i = 0, j = 0; i < sizeof(str); i++) 
{

   strptr[strcnt] = realloc(strptr[strcnt], j + 2); 
   //here, you resize each time to provide space for additional character using realloc() 
   char c = *(str + i);

   printf("%c", c);

   if(c == ',') 
   {
     ++strcnt;
     j=0;
     continue; //use a continue here
   }

   strptr[strcnt][j] = c;
   strptr[strcnt][++j] = '\0'; 
   //to provide null terminating character at the end of string (updated to next position at every iteration)
}

---

don't forget to free() the allocated memory

for( i=0; i<2; i++)
{
    printf("%s\n", strptr[i]); //just to display the string before `free`ing
    free(strptr[i]);
}

free(strptr);

---

Altogether your code would be something like this:

char str[] = "00ab00,00cd00";
char **strptr;

int i, j;
int strcnt; 

strptr = malloc(sizeof(char*) * 2);
for(i = 0; i < 2; i++)
{
    strptr[i] = malloc(1); 
}
strcnt = 0;


for(i = 0, j = 0; i < sizeof(str); i++) 
{

   strptr[strcnt] = realloc(strptr[strcnt], j + 2); 
   char c = *(str + i);

   printf("%c", c);

   if(c == ',') 
   {
     ++strcnt;
     j=0;
     continue;
   }

   strptr[strcnt][j] = c;
   strptr[strcnt][++j] = '\0';
}

for( i=0; i<2; i++)
{
    printf("%s\n", strptr[i]);
    free(strptr[i]);
}

free(strptr);

return 0;