From f7035dd3ff665dce14657cf244c10c2d4b2b43c7 Mon Sep 17 00:00:00 2001
From: k0kubun <k0kubun@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Sun, 14 Apr 2019 07:10:34 +0000
Subject: [PATCH] Do not reset non-increment-only counters

to prevernt underflow.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@67545 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 debug_counter.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/debug_counter.c b/debug_counter.c
index 4a0655380f..b9c32c1d15 100644
--- a/debug_counter.c
+++ b/debug_counter.c
@@ -47,7 +47,16 @@ VALUE
 rb_debug_counter_reset(void)
 {
     for (int i = 0; i < RB_DEBUG_COUNTER_MAX; i++) {
-        rb_debug_counter[i] = 0;
+        switch (i) {
+          case RB_DEBUG_COUNTER_mjit_length_unit_queue:
+          case RB_DEBUG_COUNTER_mjit_length_active_units:
+          case RB_DEBUG_COUNTER_mjit_length_compact_units:
+            // These counters may be decreased and should not be reset.
+            break;
+          default:
+            rb_debug_counter[i] = 0;
+            break;
+        }
     }
     return Qnil;
 }