From ce94add7fbef17cbfa10de6a5554455542e1081c Mon Sep 17 00:00:00 2001
From: Peter Zhu <peter@peterzhu.ca>
Date: Tue, 2 Sep 2025 15:24:13 +0200
Subject: [PATCH] Fix global variable counter for alias

If we alias two variable multiple times, for example like this:

    alias $foo $bar
    alias $foo $bar

Then we will increment the counter for entry2->var->counter each time,
which is not correct because we are not adding more references to
entry2->var. This reports as a memory leak in RUBY_FREE_AT_EXIT because
entry2->var->counter will never reach 0 and thus will never be freed.
---
 variable.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/variable.c b/variable.c
index ef35cf39903dc6..b1782a01c85c93 100644
--- a/variable.c
+++ b/variable.c
@@ -1164,7 +1164,7 @@ rb_alias_variable(ID name1, ID name2)
                 free_global_variable(var);
             }
         }
-        if (entry1) {
+        if (entry1->var != entry2->var) {
             entry2->var->counter++;
             entry1->var = entry2->var;
         }