I installed DDD through MacPorts on a Mac computer with OSX 10.11 El Capitan. Just after, when I ran ddd at the Terminal, it threw "Error: Unresolved inheritance operation". The contents of the ~/.ddd/log file are as follows:
GNU DDD 3.3.12 (i386-apple-darwin15.5.0)
Copyright (C) 1995-1999 Technische Universit‰t Braunschweig, Germany.
Copyright (C) 1999-2001 Universit‰t Passau, Germany.
Copyright (C) 2001 Universit‰t des Saarlandes, Germany.
Copyright (C) 2001-2009 Free Software Foundation, Inc.
Compiled with GCC 4.2.1 Compatible Apple LLVM 7.3.0 (clang-703.0.31)
Requires X11R6, Xt11R6, Motif 2.3.4 (Motif Version 2.3.4)
Includes XPM 3.4.11, Athena Panner (7000002L), Manual, App defaults, DDD core
Built 2016-06-07 by (unknown).
$ ddd
! Xt error: Unresolved inheritance operation
! Xt error
! Cannot save options
--
Emily Lynn Ragan
University of Richmond, Class of 2019
Academic Computing Services, Math and Computer Science Assistant