On the type accuracy of garbage collection

We describe a novel approach to obtaining type-accurate information for garbage collection in a hardware and language independent way. Our approach uses a run-time analysis to propagate pointer/non-pointer information from significant type events (such as allocation, which always returns a pointer). We use this technique to perform a detailed comparison of garbage collectors with different levels of accuracy and explicit deallocation on a range of C programs. We take advantage of the portability of our approach to conduct our experiments on three hardware platforms, Alpha/Digital UNIX 4.0D, Pentium/Linux 2.2, and SPARC/Solaris 2. We find that the choice of hardware platform (which includes the architecture, operating system, and libraries) greatly affects whether or not type accuracy enhances a garbage collector's ability to reclaim objects.