c - Problems with pointers and allocation - c

Question

I have to dynamically allocate a pointer inside a while.
char * allocationg_memory(char [] path p) {
char message[4000];
char c;
unsigned int i = 0;
unsigned int count;
FILE *f;
//open the file
f = fopen(p, "rt");
count = 0;
//copy the contain of the file in message
if (f) {
while ((c = getc(f)) != EOF) {
count++;
message[i] = c;
i++;
}
fclose(f);
}
//allocating the memory
char *str = (char *) malloc(sizeof (char) * (count));
if (str == NULL) {
printf("error allocating memory for string\n");
exit(1);
}
//copy the message
strncpy (str, message, count);
return str;
}
void main {
char * ptr;
do {
//my path dynamically changing
path = path_of_file;
ptr = allocating_memory(path);
printf("%s", ptr);
free(ptr);
} while (1);
}
If I set ptr = NULL it gives me segmentation fault, if I don't, if the next print is bigger than the previus, the 2nd is printed over the 1st. What's wrong with my code?

Answer 1

For starters:
Your initial allocation is for 0 bytes.
You are trying to print what you have allocated as if it were a string.
Your loop never ends.

Answer 2

This works for me. Hopefully it helps
#include<stdlib.h>
#include<stdio.h>
#include<string.h>
char * allocating_memory(int c) {
char *str = malloc ( c + 1); // allow an extra for the null
strncpy ( str, "abcdefghijklmnopqustuvwxyx", c);
str[c] = '\0'; // make sure the string is null terminated
return str;
}
int main () {
char * ptr;
int counter = 2;
do {
ptr = NULL;
ptr = allocating_memory(counter);
printf("%s\n", ptr);
free(ptr);
counter++;
} while (counter < 27);
return 0;
}