Segmentation fault on calling function more then once - c

Question

running this function more then once will cause a Segmentation fault and i cannot figure out why. Im not looking for alternative ways to split a string.
SplitX will continue splitting for x ammount of delimiters (be it '|' or '\0') and return the x or the number of substrings it could make.
I should note i have just restarted coding in C after 3 years of easy JavaScript and PHP so i could be missing something obvious.
int splitX(char **array, char *string, int x) {
int y;
int z;
int index = 0;
int windex = 0;
for(y = 0; y < x; y++) {
z = index;
while(string[index] != '\0' && string[index] != '|') {
index++;
}
char **tempPtr = realloc(array, (y+1)*sizeof(char *));
if(tempPtr == NULL) {
free(array);
return -3;
}
array = tempPtr;
array[y] = malloc(sizeof(char) * (index - z + 1));
windex = 0;
for(; z < index; z++) {
array[y][windex] = string[z];
windex++;
}
array[y][windex] = '\0';
if(string[index] == '\0')
break;
index++;
}
return y+1;
}
int main() {
char **array;
int array_len = splitX(array, query, 2);
printf("%s %s %d\n", array[0], array[1], array_len);
while(array_len > 0) {
free(array[array_len-1]);
array_len--;
}
free(array);
array_len = splitX(array, "1|2\0", 2);
printf("%s %s %d\n", array[0], array[1], array_len);
while(array_len > 0) {
free(array[array_len-1]);
array_len--;
}
free(array);
}

Answer 1

char **array;
int array_len = splitX(array, query, 2);
This lets splitX() use the uninitialized array, which results in undefined behavior.
Furthermore, C has no pass-by-reference - when you write
array = tempPtr;
inside the function, that has no visible effect outside it.
Im not looking for alternative ways to split a string.
You should really be. Your current approach is at best non-idiomatic, but it also has some other mistakes (like returning y + 1 for some reason where y would do certainly, etc.).
You are also reinventing the wheel: for string and character searching, use strstr(), strchr() and strtok_r() from the C standard library; for duplicaitng a string, use strdup() instead of going through the string manually, etc., etc...
What else:
use size_t for sizes instead of int;
maintain const correctness by using const char * for input strings.
char **split(const char *s, size_t *sz)
{
char **r = NULL;
size_t n = 0, allocsz = 0;
const char *p = s, *t = p;
int end = 0;
do {
const char *tmp = strchr(p, '|');
if (tmp == NULL) {
p = p + strlen(p);
end = 1;
} else {
p = tmp;
}
if (++n > allocsz) {
if (allocsz == 0)
allocsz = 4;
else
allocsz <<= 1;
char **tmp = realloc(r, sizeof(*r) * allocsz);
if (!tmp) abort(); // or whatever, handle error
r = tmp;
}
r[n - 1] = malloc(p - t + 1);
memcpy(r[n - 1], t, p - t);
r[n - 1][p - t] = 0;
p++;
t = p;
} while (!end);
*sz = n;
return r;
}