Make GC.latest_gc_info return :state for StackProf

gc/mmtk.c

@@ -1223,6 +1223,17 @@ rb_gc_impl_latest_gc_info(void *objspace_ptr, VALUE hash_or_key)
         rb_bug("gc_info_decode: non-hash or symbol given");
     }
 
+#define SET(name, attr) \
+    if (key == ID2SYM(rb_intern_const(#name))) \
+        return (attr); \
+    else if (hash != Qnil) \
+        rb_hash_aset(hash, ID2SYM(rb_intern_const(#name)), (attr));
+
+    /* Hack to get StackProf working because it calls rb_gc_latest_gc_info with
+     * the :state key and expects a result. This always returns the :none state. */
+    SET(state, ID2SYM(rb_intern_const("none")));
+#undef SET
+
     if (!NIL_P(key)) {
         // Matched key should return above
         return Qundef;

spec/mmtk.mspec

@@ -1,8 +1,5 @@
 # frozen_string_literal: true
 
-# GC.latest_gc_info doesn't return anything
-MSpec.register(:exclude, "CApiGCSpecs rb_gc_latest_gc_info returns a value when symbol is given")
-MSpec.register(:exclude, "CApiGCSpecs rb_gc_latest_gc_info returns the populated hash when a hash is given")
 # Testing behaviour specific to default GC
 MSpec.register(:exclude, "GC.stat increases major_gc_count after GC is run")
 MSpec.register(:exclude, "GC.stat provides some number for heap_free_slots")