On Nov 1, 2008, at 9:38 AM, Andrew Coppin wrote:
Alberto G. Corona wrote:
Is there a way to know the number of memory references for a variable?. The runtime must know it but i do not know if this available for the program trough any low level trick
More precisely, the GC computes it each time it runs. (And only computes it precisely during a "major" pass, not the more frequent "minor" passes.)
Even this isn't quite true for most GC algorithms. The GC only needs to compute whether there is 0 or >= 1 reference to a given location (with some special weasel words for stuff with finalizers defined). If you can see it, the answer is always >=1, so this information is much less useful than you might think! Usually the clever thing you want to know is "this is the sole reference to the pointed-to object". If that's what you're interested in, try looking up "one-bit reference counting", but note that like any accurate reference counting technique it's really inefficient in practice compared to GC. [There are efficient reference counting techniques, but they defer refcount updates in various subtle ways. Also, every ref count technique requires a cycle detector.] -Jan-Willem Maessen