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From: Ngan Pham <>
Subject: Patch for GC.compact memory issue
Date: Mon, 24 May 2021 07:14:01 -0700	[thread overview]
Message-ID: <> (raw)

Hello, I'd like to submit a patch to fix an issue after running
`GC.compact`. The LOCALHOST variable is defined in Ruby and is
resolved and memoized (to `localhost`) in C once. However, the pointer
in C is not GC marked. Running `GC.compact` potentially moves the
`LOCALHOST` object in Ruby causing `localhost` to point to a bad or
empty slot. This causes `env['REMOTE_ADDR']` to  a bad object in

Some useful links:
- `GC.compact` introduced:
- My conversation with tenderlove over twitter on this issue:


diff --git a/ext/kgio/accept.c b/ext/kgio/accept.c
index f1de39d..5a5f15a 100644
--- a/ext/kgio/accept.c
+++ b/ext/kgio/accept.c
@@ -497,7 +497,14 @@ void init_kgio_accept(void)
  rb_define_const(mKgio, "SOCK_CLOEXEC", INT2NUM(SOCK_CLOEXEC));

+ /*
+ * Resolve LOCALHOST from Ruby land and memoize it for fast lookup.
+ * We have to GC mark the object since it's defined in Ruby and we
+ * don't want GC.compact to move it.
+ */
  localhost = rb_const_get(mKgio, rb_intern("LOCALHOST"));
+ rb_gc_register_mark_object(localhost);
  cKgio_Socket = rb_const_get(mKgio, rb_intern("Socket"));
  cClientSocket = cKgio_Socket;
  mSocketMethods = rb_const_get(mKgio, rb_intern("SocketMethods"));

             reply	other threads:[~2021-05-24 14:14 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-24 14:14 Ngan Pham [this message]
2021-05-24 17:22 ` Patch for GC.compact memory issue Eric Wong
2021-05-24 19:00   ` Ngan Pham
2021-05-24 20:33     ` Eric Wong
2021-05-24 21:11       ` Ngan Pham
2021-05-24 21:48         ` [PATCH] HACKING: update docs with "git request-pull" info Eric Wong
2021-05-25 16:41         ` Patch for GC.compact memory issue Aaron Patterson
2021-05-25 22:50           ` Eric Wong

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