Checking NULL pointer segmentation fault in C - c

Question

I have to split an initial char and create a list of said char which has to end with a NULL so i can iterate over in the main without knowing list size. The problem is that i get a seg fault whenever i try to check if last element is NULL. i am sorry i am still trying to learn both C and english. Thank you all
#include <stdlib.h>
#include <stdio.h>
char **split(const char *s) {
char **split;
unsigned m_size = 0, c_size, i, j, k;
// get s size
for (i = 0; s[i] != '\0'; i++) {
if (s[i] == ' ') {
m_size++;
}
}
m_size++;
split = (char**) malloc(sizeof(char) * (m_size + 1));
int sizes[m_size];
c_size = 0;
// get s words size
for (i = 0, j = 0; s[i] != '\0'; i++) {
if (s[i] == ' ') {
c_size++;
sizes[j] = c_size;
c_size = 0;
j++;
} else {
c_size++;
}
}
sizes[j] = c_size;
for (i = 0; i < m_size; i++) {
split[i] = (char *) malloc(sizeof(char) * sizes[i]);
}
split[i] = NULL;
for (i = 0, j = 0, k = 0; s[i] != '\0'; i++) {
if (s[i] != ' ') {
split[j][k] = s[i];
k++;
} else {
split[j][k] = '\0';
j++;
k = 0;
}
}
return split;
}
int main() {
char s[19] = "hello how are you?";
char **splitted;
unsigned i;
splitted = split(s);
if (splitted == NULL) {
return 1;
}
for (i = 0; splitted[i]!=NULL; i++) {
printf("%s\n", splitted[i]);
}
return 0;
}
EDIT
#include <stdlib.h>
#include <stdio.h>
char **split(const char *s) {
char **r;
unsigned word_size = 0;
unsigned list_size = 0, i, j, k;
// get s size
for (i = 0; s[i] != '\0'; i++) {
if (s[i] != ' ') {
word_size++;
} else {
if (word_size > 0) {
list_size++;
word_size = 0;
}
}
}
list_size++;
r = malloc(sizeof(*r) * (list_size + 1));
int char_sizes[list_size];
for (i = 0; i < list_size; char_sizes[i] = 0, i++);
// get s words size
for (i = 0, j = 0; s[i] != '\0'; i++) {
if (s[i] != ' ') {
char_sizes[j]++;
} else {
if (char_sizes[j] > 0) {
j++;
}
}
}
for (i = 0; i < list_size; i++) {
r[i] = malloc(sizeof(char) * char_sizes[i]);
}
r[i] = NULL;
for (i = 0, j = 0, k = 0; s[i] != '\0'; i++) {
if (s[i] != ' ') {
r[j][k] = s[i];
k++;
} else {
if (k > 0) {
r[j][k] = '\0';
j++;
k = 0;
}
}
}
return r;
}
void destroy(char **list) {
unsigned i;
for (i = 0; list[i] != NULL; i++) {
free(list[i]);
}
free(list);
}
int main() {
char s[100] = " hello guys how are? you,d 31 3 ";
char **splitted;
unsigned i;
splitted = split(s);
if (splitted == NULL) {
return 1;
}
for (i = 0; splitted[i]!=NULL; i++) {
printf("%s", splitted[i]);
}
destroy(splitted);
return 0;
}
ok guys i followed your tips and i edited my code. leaving this here if someone wants to point out other errors i will appreciate. now it should work even with multiple spaces. thanks to all

Answer 1

Your are requesting an "array" of pointers to char, but you are allocating an "array" of chars:
split = (char**) malloc(sizeof(char) * (m_size + 1));
should become
split = malloc(sizeof(char*) * (m_size + 1));
Note the sizeof(char*). BTW: Note that in C, you should not cast the result of malloc as explained in this SO post.