kilo commentary: realloc is not magic

I'm now starting the "make this an actual text editor" part of implementing kilo. The first step, naturally, is to write code that inserts a new character. Here's the implementation of editorRowInsertChar given in step 101:

void editorRowInsertChar(erow *row, int at, int c) {
  if (at < 0 || at > row->size) at = row->size;
  row->chars = realloc(row->chars, row->size + 2);
  memmove(&row->chars[at + 1], &row->chars[at], row->size - at + 1);
  row->size++;
  row->chars[at] = c;
  editorUpdateRow(row);
}

So yeah, hence the title of this post. The call of memmove every time a character is inserted is pretty bad, too. But... well, this is actually probably good enough for a toy editor that no one is actually going to use for real editing work. Still, I wish the author had at least mentioned that this is very much a quick-and-dirty way to do it, and that there's better ways to do it.