Make Pitch::to_string() more robust

lily/pitch.cc

 /*
   This file is part of LilyPond, the GNU music typesetter.
 
   Copyright (C) 1998--2020 Han-Wen Nienhuys <hanwen@xs4all.nl>
 
   LilyPond is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
 
@@ skipping 140 matching lines @@
 char const *accname[] = {"eses", "eseh", "es", "eh", "",
                          "ih", "is", "isih", "isis"
                         };
 
 string
 Pitch::to_string () const
 {
   int n = (notename_ + 2) % scale_->step_count ();
   string s (1, static_cast<char> (n + 'a'));
   Rational qtones = alteration_ * Rational (4, 1);
-  int qt = int (rint (Real (qtones)));
+  size_t qt = size_t (rint (Real (qtones) + 4.0));
+  if (qt < sizeof (accname) / sizeof (accname[0]))
+    {
+      s += string (accname[qt]);
+    }
+  else
+    {
+      s += "??";
+    }
 
-  s += string (accname[qt + 4]);
   if (octave_ >= 0)
     {
       int o = octave_ + 1;
       while (o--)
         s += "'";
     }
   else if (octave_ < 0)
     {
       int o = (-octave_) - 1;
       while (o--)
@@ skipping 126 matching lines @@
 Rational NATURAL_ALTERATION (0);
 Rational FLAT_ALTERATION (-1, 2);
 Rational DOUBLE_FLAT_ALTERATION (-1);
 Rational SHARP_ALTERATION (1, 2);
 
 Pitch
 Pitch::negated () const
 {
   return pitch_interval (*this, Pitch ());
 }