get size of malloc'd object

[Andrew Koenig]

There is a very simple way to do this portably:

	struct chunk {
		unsigned size;
		char *mem;
	};

	struct chunk
	challoc (n)
		unsigned n;
	{
		struct chunk ch;
		ch.size = n;
		ch.mem = malloc (n);
		return ch;
	}

	void
	chfree (ch)
		struct chunk ch;
	{
		if (ch.mem)
			free (ch.mem);
	}

Now rewrite your program to deal with memory through chunk structures
instead of through simple pointers.  It should be possible to make this
easier by using macros.