From GridLAB-D Wiki
gdb - Control the use of the source debugger for runtime classes
Synopsis
host% gridlabd -D gdb=0|1 host% gridlabd --define gdb=0|1 #set gdb=0|1
Description
When gdb is non-zero, runtime classes are built with debugging enabled and GridLAB-D is started inside the host platform's debugging environment. This is specifically to allow user to debug runtime classes.
The gdb option interacts in complex ways with debug, gdb_window, compile_once, and use_msvc. For details, see further documentation on working with MS Visual Studio 2005 in GridLAB-D.