Restore asserts and error handling

A couple of them got improved out of existence.

src/frontend/terminaloverlay.cc

@@ -298,8 +298,9 @@ void NotificationEngine::apply( Framebuffer &fb ) const
       }
       break;
     case -1: /* unprintable character */
-    default: /* Bogus width, ignore. */
       break;
+    default:
+      assert( !"unexpected character width from wcwidth()" );
     }
   }
 }

src/network/network.cc

@@ -335,7 +335,8 @@ bool Connection::try_bind( const char *addr, int port_low, int port_high )
     if ( bind( sock(), &local_addr.sa, local_addr_len ) == 0 ) {
       set_MTU( local_addr.sa.sa_family );
       return true;
-    } else if ( i == search_high ) { /* last port to search */
+    } // else fallthrough to below code, on last iteration.
+  }
   int saved_errno = errno;
   socks.pop_back();
   char host[ NI_MAXHOST ], serv[ NI_MAXSERV ];
@@ -349,10 +350,6 @@ bool Connection::try_bind( const char *addr, int port_low, int port_high )
 	   host, serv );
   throw NetworkException( "bind", saved_errno );
 }
-  }
-
-  return false;
-}
 
 Connection::Connection( const char *key_str, const char *ip, const char *port ) /* client */
   : socks(),
@@ -456,7 +453,7 @@ string Connection::recv( void )
     prune_sockets();
     return payload;
   }
-  return "";
+  throw NetworkException( "No packet received" );
 }
 
 string Connection::recv_one( int sock_to_recv, bool nonblocking )

src/statesync/user.cc

@@ -95,6 +95,7 @@ string UserStream::diff_from( const UserStream &existing ) const
       }
       break;
     default:
+      assert( !"unexpected event type" );
       break;
     }
 
@@ -130,6 +131,7 @@ const Parser::Action &UserStream::get_action( unsigned int i ) const
   case ResizeType:
     return actions[ i ].resize;
   default:
+    assert( !"unexpected action type" );
     static const Parser::Ignore nothing = Parser::Ignore();
     return nothing;
   }

src/statesync/user.h

@@ -85,7 +85,7 @@ namespace Network {
     /* interface for Network::Transport */
     void subtract( const UserStream *prefix );
     string diff_from( const UserStream &existing ) const;
-    string init_diff( void ) const { return string(); };
+    string init_diff( void ) const { return diff_from( UserStream() ); };
     void apply_string( const string &diff );
     bool operator==( const UserStream &x ) const { return actions == x.actions; }
 

src/terminal/terminal.cc

@@ -140,7 +140,9 @@ void Emulator::print( const Parser::Print *act )
     }
     break;
   case -1: /* unprintable character */
-  default: /* bogus width, ignore */
+    break;
+  default:
+    assert( !"unexpected character width from wcwidth()" );
     break;
   }
 }

src/terminal/terminaluserinput.cc

@@ -46,6 +46,9 @@ string UserInput::input( const Parser::UserByte *act,
   /* We need to look ahead one byte in the SS3 state to see if
      the next byte will be A, B, C, or D (cursor control keys). */
 
+  /* This doesn't handle the 8-bit SS3 C1 control, which would be
+     two octets in UTF-8. Fortunately nobody seems to send this. */
+
   switch ( state ) {
   case Ground:
     if ( act->c == 0x1b ) { /* ESC */
@@ -74,8 +77,8 @@ string UserInput::input( const Parser::UserByte *act,
     }
 
   default:
-    /* This doesn't handle the 8-bit SS3 C1 control, which would be
+    assert( !"unexpected state" );
-       two octets in UTF-8. Fortunately nobody seems to send this. */
+    state = Ground;
     return string();
   }
 }