read lines c

#include <stdio.h>
#include <stdlib.h>
#define NULL_CHECK(p) if (p == NULL) return NULL;
#define CHUNK_CHARS 32
#define CHUNK_POINTERS 8

char *readLine(FILE *file) {
  char *line = NULL, ch;
  int index = 0, currSize = 0;
  while ((ch = fgetc(file)) != EOF) {
    if (index == currSize) {
      currSize += CHUNK_CHARS;
      line = realloc(line, sizeof(char) * currSize);
      NULL_CHECK(line);
    }
    if (ch != '\n') {
      line[index++] = ch;
    } else {
      break;
    }
  }
  NULL_CHECK(line);
  if (index == currSize) {
    currSize++;
    line = realloc(line, sizeof(char) * currSize);
  } else {
    currSize = index + 1;
    line = realloc(line, sizeof(char) * currSize);
  }
  NULL_CHECK(line);
  line[index] = 0;
  return line;
}

char **readLines(FILE *file) {
  char **lines = NULL, *line = NULL;
  int index = 0, currSize = 0;
  while ((line = readLine(file)) != NULL) {
    if (index == currSize) {
      currSize += CHUNK_POINTERS;
      lines = realloc(lines, sizeof(char*) * currSize);
      NULL_CHECK(lines);
    }
    lines[index++] = line;
  }
  NULL_CHECK(lines);
  if (index == currSize) {
    currSize++;
    lines = realloc(lines, sizeof(char*) * currSize);
  } else {
    currSize = index + 1;
    lines = realloc(lines, sizeof(char*) * currSize);
  }
  NULL_CHECK(lines);
  lines[index] = NULL;
  return lines;
}

void free2d(char **p2p) {
  for (int i = 0; p2p[i] != NULL; i++) {
    free(p2p[i]);
  }
  free(p2p);
}

void writeLines(char **lines) {
  for (int i = 0; lines[i] != NULL; i++) {
    puts(lines[i]);
  }
}

int main(void) {
  char **lines = NULL;
  lines = readLines(stdin);
  writeLines(lines);
  free2d(lines);
  return 0;
}