Demo: Copy a File Using a Heap Buffer

The second of three variants of the same file-copy program. This one asks the C runtime for its buffer at run time with malloc(), which means the size need not be known when the program is compiled — and that every allocation now has to be released on every path out of the function, including the error paths.

Together with the teaching assistant you will fill in the TODOs in copy_file.c, paying particular attention to the early returns, then run the result under valgrind to confirm nothing leaks.

There are more TODOs here than in the global-buffer variant, and most of them are free() calls. That imbalance is the point of the exercise.