From 527a247ee090efb089ae68fe793ce51fb6aa720a Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Sat, 6 Jan 2024 22:47:42 -0800
Subject: eval: potential gc problem in binding.

* eval.c (reparent_env): This function is used in bindings
helper, when special variables are involved. It makes a new
environment the parent of an existing one, just by assigning
the pointer. This is wrong under generational GC if it makes
a mature object point to a new object. We fix it with the set
macro. I've not seen a crash because of this; I caught it by
inspection.
---
 eval.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/eval.c b/eval.c
index 26f4b701..1846c348 100644
--- a/eval.c
+++ b/eval.c
@@ -759,7 +759,7 @@ static val lookup_symac_lisp1(val menv, val sym)
 
 static val reparent_env(val child, val parent)
 {
-  child->e.up_env = parent;
+  set(mkloc(child->e.up_env, child), parent);
   return child;
 }
 
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