Couldn't the JIT provide me a way of allocating new blocks of memory? and freeing blocks of memory back to the 'OS'? At least allocating new blocks? I don't mi

Couldn't the JIT provide me a way of allocating new blocks of memory? and freeing blocks of memory back to the 'OS'? At least allocating new blocks? I don't mind no GC, but having to allocate the maximum memory your program will use before it starts can be painful.