Use M$FREE to release a memory block allocated by M$ALLOC. This memory is returned to the pool of memory available for use by the runtime. On most operating systems, this memory is still associated with the runtime's process, so it cannot be used by any other processes. On a few systems, this memory may be made available to the operating system for re-use by other processes.
It is an error to attempt to use a block of memory once it has been freed. It is also an error to free a block of memory more than once or to free a memory address that has never been allocated. Any of these errors can lead to memory access violations. The runtime attempts to detect these errors and avoid them, but it cannot detect all such errors.