Question: Is there any mechanism like destructors in C? Or is there another way to achieve it?

My requirement is that when a program terminates all memory allocated at runtime should be freed. I keep a list of memory that is allocated using `malloc`.

Answer: 
Another alternative is to write a memory manager.

The idea is that the memory manager allocates large blocks of memory and divides it into smaller pieces for the rest of the program to use. When the program terminates, the memory manager can just delete the large blocks.

That's the basic idea, although the memory manager may need to be more complex depending on the memory usage profile of the program.

There's a basic memory manager in the Doom source code you could examine: <http://doom.wikia.com/wiki/Zone_memory>
At application termination all memory allocated through malloc() will be freed unless the application becomes some kind of a zombie process. Normal termination should free all space otherwise.

The malloc() function uses operating system calls to allocate memory and when the process terminates the memory allocated to the process is reclaimed by the operating system.

I have seen cases of zombie processes under Windows in which a process stayed in memory hanging around until it was terminated via the Task Manager application.