Demo: Copy a File Using a Heap Buffer

The third of four variants of the file-copy program. This one asks the allocator for its buffer at run time with malloc(), which means the size need not be known when the program is compiled -- and that the buffer now has to be released on every path out of main(), including the error paths.

Together with the teaching assistant you will fill in the TODOs in copy_file.c, paying particular attention to the labels at the end of main() and to which of them each failure has to reach, then run the result under valgrind to confirm nothing leaks.

Compare the labels at the end of main() with the ones in the first two variants. That difference is the point.