don't stack states on NUL-transitions that are jams

diff --git a/gen.c b/gen.c
index 9051bf1096a2a09c7f12e2dc4b73b4c73eaf4537..d0f7d7cc31c71b91c399f9f55696bdb475d89dac 100644 (file)
--- a/gen.c
+++ b/gen.c
@@ -713,12 +713,20 @@ void gen_NUL_trans()
                (void) sprintf( NUL_ec_str, "%d", NUL_ec );
                gen_next_compressed_state( NUL_ec_str );
 
-               if ( reject )
-                       indent_puts( "*yy_state_ptr++ = yy_current_state;" );
-
                do_indent();
-
                out_dec( "yy_is_jam = (yy_current_state == %d);\n", jamstate );
+
+               if ( reject )
+                       {
+                       /* Only stack this state if it's a transition we
+                        * actually make.  If we stack it on a jam, then
+                        * the state stack and yy_c_buf_p get out of sync.
+                        */
+                       indent_puts( "if ( ! yy_is_jam )" );
+                       indent_up();
+                       indent_puts( "*yy_state_ptr++ = yy_current_state;" );
+                       indent_down();
+                       }
                }
 
        /* If we've entered an accepting state, back up; note that