[harshreality]

Recently there was a HN thread [1] about the conservative garbage collection used in some 32bit VMs (the complaint started with Go), because the way their GC works is by scanning portions of process memory for 32 bit values that map to valid address space for that process. Those values are treated as pointers even if they're not pointers, so the data they point to is assumed to be used and is not garbage collected.

Architectures/ABIs with 64bit pointers have a much lower probability of arbitrary values mapping to active memory space for the process, so memory bloat caused by the conservative GC strategy is much more limited.

The x32 abi looks like it would suffer from this 32bit conservative garbage collection problem too. Short of changing the VM strategy, using 64 bit pointers is the only way to ensure that such VMs do not accumulate so much unused but not-garbage-collectable memory allocations.

[1] http://news.ycombinator.com/item?id=3814020