Re: Compile Time Garbage Collection impossible?

A.L. wrote:


(snip)


> Determining what objects could be deallocated during compilation is
> equivalent to "halting problem" that is undecidable. i.e. there is
> no algorithm possible that could do this for all possible programs.


I don't disagree, but determining deallocation at run-time isn't so
easy, either.


In addition to circular linked lists, which as already mentioned are a
problem for reference count GC, there is memory allocated in main and
not referenced later. Those two are often indicated in Java
documentation. Consider in the main program:


double x[]=new double[100000000];
/* use x here, but never again */
/* long and complicated code goes here */


Now, throughout the rest of the program that array will remain
allocated as it is in scope. It might even be that a compile time GC
would know that there are no more references, and no path back to code
that does reference x, but at run time there is no way to know.


-- glen

Return to the comp.compilers page.
Search the comp.compilers archives again.