Update doc for ObjectSpace.memsize_of

st0012 · st0012 · commit 9eac1c3a8880 · 2025-07-23T12:24:20.000+01:00
diff --git a/ext/objspace/objspace.c b/ext/objspace/objspace.c
@@ -38,10 +38,14 @@
  *  information as only a *HINT*. Especially, the size of +T_DATA+ may not be
  *  correct.
  *
- *  This method is only expected to work with C Ruby.
- *
- *  From Ruby 2.2, memsize_of(obj) returns a memory size includes
- *  sizeof(RVALUE).
+ *  This method is only expected to work with CRuby.
+ *
+ *  From Ruby 2.2, memsize_of(obj) returns a memory size that includes
+ *  the slot size occupied by the object. Prior to Ruby 3.2, this was a
+ *  fixed size (sizeof(RVALUE)). From Ruby 3.2 with Variable Width
+ *  Allocation, this is the actual slot size used (1×, 2×, 4×, 8×, or
+ *  16× BASE_SLOT_SIZE), plus any additional memory allocated outside
+ *  the slot (such as external strings, arrays, or hash tables).
  */
 
 static VALUE
