introduce `obj_ary_extracapa`.

Introduce a new debug counter `obj_ary_extracapa` which counts
arrays which are `len < capa`.

2 files changed, 3 insertions, 0 deletions

diff --git a/array.c b/array.c
index 68f9321192..7b086f4ff9 100644
--- a/array.c
+++ b/array.c
@@ -786,6 +786,8 @@ void
 rb_ary_free(VALUE ary)
 {
     if (ARY_OWNS_HEAP_P(ary)) {
+        (void)RB_DEBUG_COUNTER_INC_IF(obj_ary_extracapa, ARY_HEAP_CAPA(ary) > RARRAY_LEN(ary));
+
         if (RARRAY_TRANSIENT_P(ary)) {
             RB_DEBUG_COUNTER_INC(obj_ary_transient);
         }
diff --git a/debug_counter.h b/debug_counter.h
index 2add2acc25..cb2222a869 100644
--- a/debug_counter.h
+++ b/debug_counter.h
@@ -206,6 +206,7 @@ RB_DEBUG_COUNTER(obj_str_fstr)
 RB_DEBUG_COUNTER(obj_ary_embed)
 RB_DEBUG_COUNTER(obj_ary_transient)
 RB_DEBUG_COUNTER(obj_ary_ptr)
+RB_DEBUG_COUNTER(obj_ary_extracapa)
 /*
   ary_shared_create: shared ary by Array#dup and so on.
   ary_shared: finished in shard.