Fix some gc-unsafe mutations found by inspection.

* eval.c (force): When replacing the promise by a
forced value, we must use the set macro.  Only the deref
assignments which store symbols are safe, not the one storing
ret.

* lib.c (alist_nremove, alist_nremove1): We must
use the set macro here instead of assigning through deref.
Even though these assignments preserve the direction of the
list (they just splice out nodes), it's possible that the list
already contains a "wrong-way" reference (old generation to
new) and that the node making this reference is appropriately
marked to be processed properly in the next GC cycle. If we
remove *that* node, we then cause its predecessor to point to
the new generation node and that predecessor could be old
generation.

2 files changed, 3 insertions, 3 deletions

diff --git a/eval.c b/eval.c
index 06df270d..a0c610c9 100644
--- a/eval.c
+++ b/eval.c
@@ -4469,7 +4469,7 @@ static val force(val promise)
     deref(pstate) = promise_inprogress_s;
     ret = funcall(deref(pval));
     deref(pstate) = promise_forced_s;
-    deref(pval) = ret;
+    set(pval, ret);
     return ret;
   } else if (deref(pstate) == promise_inprogress_s) {
     val form = second(cdr(cd));
diff --git a/lib.c b/lib.c
index aee22096..b4452cbb 100644
--- a/lib.c
+++ b/lib.c
@@ -7249,7 +7249,7 @@ val alist_nremove(val list, val keys)
 
   while (deref(plist)) {
     if (memqual(car(car(deref(plist))), keys))
-      deref(plist) = cdr(deref(plist));
+      set(plist, cdr(deref(plist)));
     else
       plist = cdr_l(deref(plist));
   }
@@ -7268,7 +7268,7 @@ val alist_nremove1(val list, val key)
 
   while (deref(plist)) {
     if (equal(car(car(deref(plist))), key))
-      deref(plist) = cdr(deref(plist));
+      set(plist, cdr(deref(plist)));
     else
       plist = cdr_l(deref(plist));
   }