[GR-18163] Fix rb_gc_register_mark_object for Float and bignum values

PullRequest: truffleruby/4231

Author: andrykonchin

CHANGELOG.md

@@ -8,14 +8,15 @@ Bug fixes:
 * Fix repeated calling of methods `Dir#{each,each_child,children}` (#3464, @andrykonchin).
 * Fix `IO#{wait,wait_readable,wait_writable}` methods and switch the current thread into a sleep state (@andrykonchin).
 * Fix `rb_global_variable()` for `Float` and bignum values during the `Init_` function (#3478, @eregon).
+* Fix `rb_gc_register_mark_object()` for `Float` and bignum values (#3502, @eregon, @andrykonchin).
 * Fix parsing literal floats when the locale does not use `.` for the decimal separator (e.g. `LANG=fr_FR.UTF-8`) (#3512, @eregon).
 
 Compatibility:
+
 * Move `IO#wait_readable`, `IO#wait_writable`, `IO#wait_priority` and `IO#wait` into core library (@andrykonchin).
 * Change assignment evaluation order for fully qualified constant and evaluate left-hand-side before right-hand-side (#3039, @andrykonchin).
 * Fix evaluation order for multi-assignment and evaluate left-hand-side before right-hand-side (@andrykonchin).
 * Add `Regexp.linear_time?` method (#3039, @andrykonchin).
-
 * Allow null encoding pointer in `rb_enc_interned_str_cstr` (@thomasmarshall).
 
 Performance:

lib/cext/ABI_check.txt

@@ -1 +1 @@
-17
+18

lib/truffle/truffle/cext.rb

@@ -1621,8 +1621,12 @@ def rb_gc
 
   GC_ROOTS = []
 
-  def rb_gc_register_mark_object(obj)
-    GC_ROOTS.push obj
+  def rb_gc_register_mark_object(value)
+    # We save the ValueWrapper here and not the actual value/object, this is important for primitives like double and
+    # not-fixnum-long, as we need to preserve the handle by preserving the ValueWrapper of that handle.
+    # For those cases the primitive cannot itself reference its ValueWrapper, unlike RubyDynamicObject and ImmutableRubyObject.
+    wrapper = Primitive.cext_to_wrapper(value)
+    GC_ROOTS.push wrapper
   end
 
   def rb_gc_latest_gc_info(hash_or_key)

spec/ruby/optional/capi/ext/gc_spec.c

@@ -16,6 +16,8 @@ VALUE registered_after_rb_global_variable_bignum;
 VALUE registered_after_rb_global_variable_float;
 VALUE rb_gc_register_address_outside_init;
 
+VALUE rb_gc_register_mark_object_not_referenced_float;
+
 static VALUE registered_tagged_address(VALUE self) {
   return registered_tagged_value;
 }
@@ -90,6 +92,10 @@ static VALUE gc_spec_rb_gc_register_mark_object(VALUE self, VALUE obj) {
   return Qnil;
 }
 
+static VALUE gc_spec_rb_gc_register_mark_object_not_referenced_float(VALUE self) {
+  return rb_gc_register_mark_object_not_referenced_float;
+}
+
 void Init_gc_spec(void) {
   VALUE cls = rb_define_class("CApiGCSpecs", rb_cObject);
 
@@ -115,6 +121,9 @@ void Init_gc_spec(void) {
   registered_after_rb_global_variable_float = DBL2NUM(6.28);
   rb_global_variable(&registered_after_rb_global_variable_float);
 
+  rb_gc_register_mark_object_not_referenced_float = DBL2NUM(1.61);
+  rb_gc_register_mark_object(rb_gc_register_mark_object_not_referenced_float);
+
   rb_define_method(cls, "registered_tagged_address", registered_tagged_address, 0);
   rb_define_method(cls, "registered_reference_address", registered_reference_address, 0);
   rb_define_method(cls, "registered_before_rb_gc_register_address", get_registered_before_rb_gc_register_address, 0);
@@ -131,6 +140,7 @@ void Init_gc_spec(void) {
   rb_define_method(cls, "rb_gc", gc_spec_rb_gc, 0);
   rb_define_method(cls, "rb_gc_adjust_memory_usage", gc_spec_rb_gc_adjust_memory_usage, 1);
   rb_define_method(cls, "rb_gc_register_mark_object", gc_spec_rb_gc_register_mark_object, 1);
+  rb_define_method(cls, "rb_gc_register_mark_object_not_referenced_float", gc_spec_rb_gc_register_mark_object_not_referenced_float, 0);
   rb_define_method(cls, "rb_gc_latest_gc_info", gc_spec_rb_gc_latest_gc_info, 1);
 }
 

spec/ruby/optional/capi/gc_spec.rb

@@ -108,6 +108,10 @@
     it "can be called with an object" do
       @f.rb_gc_register_mark_object(Object.new).should be_nil
     end
+
+    it "keeps the value alive even if the value is not referenced by any Ruby object" do
+      @f.rb_gc_register_mark_object_not_referenced_float.should == 1.61
+    end
   end
 
   describe "rb_gc_latest_gc_info" do

src/main/c/cext/gc.c

@@ -65,7 +65,8 @@ VALUE rb_gc_latest_gc_info(VALUE key) {
 }
 
 void rb_gc_register_mark_object(VALUE obj) {
-  RUBY_CEXT_INVOKE_NO_WRAP("rb_gc_register_mark_object", obj);
+  // No rb_tr_unwrap() here as the caller actually wants a ValueWrapper or a handle
+  polyglot_invoke(RUBY_CEXT, "rb_gc_register_mark_object", obj);
 }
 
 void* rb_tr_read_VALUE_pointer(VALUE *pointer) {