X-Git-Url: https://git.donarmstrong.com/?a=blobdiff_plain;f=lily%2Fprotected-scm.cc;h=a9fabdc4f2e6fa69803b4c2aaa2c3583039d2154;hb=c991eb5d49a1b36c81a890c4574f75d8834bb9a0;hp=225c64dc60fc220bf03910f25575a539a3ecbdfd;hpb=28d702692ec7fa5f4de6a60a7e165ec3305a5daf;p=lilypond.git

diff --git a/lily/protected-scm.cc b/lily/protected-scm.cc
index 225c64dc60..a9fabdc4f2 100644
--- a/lily/protected-scm.cc
+++ b/lily/protected-scm.cc
@@ -37,18 +37,20 @@ Protected_scm::Protected_scm (SCM s)
   assert (SCM_IMP (s));
 }
 
-// For static objects, this will be called at program exit.  With the
-// state of the memory system unknown, we refrain from any cleanup
-// actions outside of the object memory itself.
+SCM Protected_scm::list_ = SCM_EOL;
+SCM Protected_scm::last_ = SCM_EOL;
 
-Protected_scm::~Protected_scm ()
+void
+Protected_scm::protectify (SCM s)
 {
-  object_ = SCM_UNDEFINED;
+  s = scm_list_1 (s);
+  if (SCM_CONSP (last_))
+    SCM_SETCDR (last_, s);
+  else
+    list_ = scm_permanent_object (s);
+  last_ = object_ = s;
 }
 
-SCM Protected_scm::list_ = SCM_EOL;
-SCM Protected_scm::last_ = SCM_EOL;
-
 Protected_scm &
 Protected_scm::operator = (SCM s)
 {
@@ -57,14 +59,7 @@ Protected_scm::operator = (SCM s)
   else if (SCM_IMP (s))
     object_ = s;
   else
-    {
-      s = scm_list_1 (s);
-      if (SCM_CONSP (last_))
-        SCM_SETCDR (last_, s);
-      else
-        list_ = scm_permanent_object (s);
-      last_ = object_ = s;
-    }
+    protectify (s);
 
   return *this;
 }
@@ -75,7 +70,19 @@ Protected_scm::operator = (Protected_scm const &s)
   return *this = (SCM) s;
 }
 
-Protected_scm::operator SCM () const
+Protected_scm::operator SCM const & () const
 {
-  return SCM_CONSP (object_) ? SCM_CAR (object_) : object_;
+  if (SCM_CONSP (object_))
+    return *SCM_CARLOC (object_);
+  return object_;
+}
+
+Protected_scm::operator SCM & ()
+{
+  // The reference may be used to overwrite an immediate value with a
+  // non-immediate one, so we _have_ to create full protection.
+  if (!SCM_CONSP (object_))
+    protectify (object_);
+
+  return *SCM_CARLOC (object_);
 }