Basically, I followed the tips to conduct things as following steps. However, I got errors showing "No file", "No symbol "MAIN" in current context" and "No source file for address MAIN" ... etc.
(1) compile the code using these ifort options: -extend-source 132 -O0 -g -save-temps -fpic -Wl,-no_pie
(2) run the DDD with idb: ddd --ladebug --debugger idb my_program
The DDD GUI window showed the following messages: