Implement Write Barrier and dsize for FFI::Pointer

As well as FFI::MemoryPointer and FFI::AbstractMemory

Write barrier protected objects are allowed to be promoted to the old generation, which means they only get marked on major GC.

The downside is that the RB_BJ_WRITE macro MUST be used to set references, otherwise the referenced object may be garbaged collected.

This commit also implement a dsize function so that these instance report a more relevant size in various memory profilers.

1 files changed, 8 insertions, 0 deletions

diff --git a/spec/ffi/pointer_spec.rb b/spec/ffi/pointer_spec.rb
index 9c85da7..c8242c7 100644
--- a/spec/ffi/pointer_spec.rb
+++ b/spec/ffi/pointer_spec.rb
@@ -381,5 +381,13 @@ describe "AutoPointer" do
       expect(mptr[1].read_uint).to eq(0xcafebabe)
     end
   end
+
+  it "has a memsize function", skip: RUBY_ENGINE != "ruby" do
+    base_size = ObjectSpace.memsize_of(Object.new)
+
+    pointer = FFI::Pointer.new(:int, 0xdeadbeef)
+    size = ObjectSpace.memsize_of(pointer)
+    expect(size).to be > base_size
+  end
 end