Interesting talk. It seems there are a few features D could
provide which would make for some more powerful GCs:
- Hook for when generating code which reads/writes a pointer
allowing GC to put in read/write barriers where necessary.
- Hook for union assignment so that the GC could emplace the
correct type bits
- Hook for passing pointers to extern(XXX) functions so that the
GC can pin the arguments allowing a compacting GC
- Hook for function call/return so that stack type-info can be
stored. There's actually another way to do this which would have
less overhead - at compile time the compiler could write the
address range of each function along with a bitmap for possible
pointers in that function to some known location. When the GC
runs it could unwind the stack and look each frame pointer up in
the list of functions to find the bit pattern to use. When
calling a function that does some low-level stuff and might
prevent the unwinding from working correctly it would be possible
to switch back to conservative mode until the function returns.
