From 08c5bc3ff87e25b1b575283f91546e5f77c591a5 Mon Sep 17 00:00:00 2001
From: Devon Schudy <dschudy@gmail.com>
Date: Wed, 26 Mar 2014 14:58:20 -0400
Subject: [PATCH] Fix infinite loop in Completion_heads_engraver at invalid
 measure position (issue 3888).

* Completion_heads_engraver now gives a programming_error instead of trying to make negative-duration notes.
* intlog2 with a nonpositive argument now gives an error instead of an infinite loop.
---
 lily/completion-note-heads-engraver.cc | 6 ++++++
 lily/misc.cc                           | 3 ++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/lily/completion-note-heads-engraver.cc b/lily/completion-note-heads-engraver.cc
index 5775ef188a..4192b58be1 100644
--- a/lily/completion-note-heads-engraver.cc
+++ b/lily/completion-note-heads-engraver.cc
@@ -117,6 +117,12 @@ Completion_heads_engraver::next_moment (Rational const &note_len)
     }
 
   Moment result = *l - *e;
+  if (result < 0)
+    {
+      programming_error ("invalid measure position: "
+                         + e->to_string () + " of " + l->to_string ());
+      return 0;
+    }
   Moment const *unit = unsmob_moment (get_property ("completionUnit"));
 
   if (unit)
diff --git a/lily/misc.cc b/lily/misc.cc
index f104f98baa..2adc250481 100644
--- a/lily/misc.cc
+++ b/lily/misc.cc
@@ -30,7 +30,8 @@
 int
 intlog2 (int d)
 {
-  assert (d);
+  if (d <= 0)
+    error ("intlog2 with negative argument: " + to_string (d));
   int i = 0;
   while ((d != 1))
     {
-- 
2.39.2