Fix rb_global_variable() for Float and bignum values during the Init_ function

* We need to store the ValueWrapper and not the value/object itself in GC_REGISTERED_ADDRESSES,
  see #3478 (comment)
* Fixes #3478

Author: eregon

CHANGELOG.md

@@ -7,6 +7,7 @@ Bug fixes:
 * Add missing thread-safe objects write barriers for `TruffleRuby::ConcurrentMap` (#3179, @eregon).
 * 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).
 
 Compatibility:
 * Move `IO#wait_readable`, `IO#wait_writable`, `IO#wait_priority` and `IO#wait` into core library (@andrykonchin).

lib/cext/ABI_check.txt

@@ -1 +1 @@
-14
+15

lib/truffle/truffle/cext.rb

@@ -214,11 +214,15 @@ def init_extension(library, library_path)
     function_name = "Init_#{name}"
 
     init_function = library[function_name]
-    begin
-      Primitive.call_with_c_mutex_and_frame(VOID_TO_VOID_WRAPPER, [init_function], nil, nil)
-    ensure
-      resolve_registered_addresses
-    end
+
+    Primitive.call_with_c_mutex_and_frame(-> {
+      begin
+        Primitive.interop_execute(VOID_TO_VOID_WRAPPER, [init_function])
+      ensure
+        # Resolve while inside the ExtensionCallStackEntry to ensure the preservedObjects are still all alive
+        resolve_registered_addresses
+      end
+    }, [], nil, nil)
   end
 
   def supported?
@@ -2238,15 +2242,19 @@ def rb_gc_register_address(address)
     else
       # Read it immediately if outside Init_ function.
       # This assumes the value is already set when this is called and does not change after that.
-      GC_REGISTERED_ADDRESSES[address] = LIBTRUFFLERUBY.rb_tr_read_VALUE_pointer(address)
+      register_address(address)
     end
   end
 
   def resolve_registered_addresses
-    c_global_variables = Primitive.fiber_c_global_variables
-    c_global_variables.each do |address|
-      GC_REGISTERED_ADDRESSES[address] = LIBTRUFFLERUBY.rb_tr_read_VALUE_pointer(address)
-    end
+    Primitive.fiber_c_global_variables.each { |address| register_address(address) }
+  end
+
+  private def register_address(address)
+    # 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.
+    GC_REGISTERED_ADDRESSES[address] = Primitive.cext_to_wrapper LIBTRUFFLERUBY.rb_tr_read_VALUE_pointer(address)
   end
 
   def rb_gc_unregister_address(address)

src/main/c/cext/gc.c

@@ -69,8 +69,8 @@ void rb_gc_register_mark_object(VALUE obj) {
 }
 
 void* rb_tr_read_VALUE_pointer(VALUE *pointer) {
-  VALUE value = *pointer;
-  return rb_tr_unwrap(value);
+  // No rb_tr_unwrap() here as the caller actually wants a ValueWrapper or a handle
+  return *pointer;
 }
 
 int rb_during_gc(void) {

src/main/java/org/truffleruby/cext/CExtNodes.java

@@ -1791,11 +1791,10 @@ Object sym2id(RubySymbol symbol,
     public abstract static class WrapValueNode extends PrimitiveArrayArgumentsNode {
 
         @Specialization
-        Object wrapInt(Object value,
+        ValueWrapper wrap(Object value,
                 @Cached WrapNode wrapNode) {
             return wrapNode.execute(value);
         }
-
     }
 
     @Primitive(name = "cext_unwrap")
@@ -1820,6 +1819,21 @@ private String exceptionMessage(Object value) {
         }
     }
 
+    @Primitive(name = "cext_to_wrapper")
+    public abstract static class CExtToWrapperNode extends PrimitiveArrayArgumentsNode {
+        @Specialization
+        ValueWrapper toWrapper(Object value,
+                @Cached UnwrapNode.ToWrapperNode toWrapperNode) {
+            ValueWrapper wrapper = toWrapperNode.execute(this, value);
+            if (wrapper == null) {
+                CompilerDirectives.transferToInterpreterAndInvalidate();
+                throw CompilerDirectives.shouldNotReachHere("ValueWrapper not found for " + value);
+            }
+            return wrapper;
+        }
+    }
+
+
     @CoreMethod(names = "create_mark_list", onSingleton = true, required = 1)
     public abstract static class NewMarkerList extends CoreMethodArrayArgumentsNode {
 
@@ -1837,7 +1851,7 @@ Object createNewMarkList(RubyDynamicObject object,
     public abstract static class AddToMarkList extends CoreMethodArrayArgumentsNode {
 
         @Specialization
-        Object addToMarkList(Object markedObject,
+        Object rbGCMark(Object markedObject,
                 @Cached InlinedBranchProfile noExceptionProfile,
                 @Cached UnwrapNode.ToWrapperNode toWrapperNode) {
             ValueWrapper wrappedValue = toWrapperNode.execute(this, markedObject);