GDB for IEC 61131-3 Debugging?

In my musings today, I started to give thought as to some of the mechanics associated with the implementation of a debugging interface for the IEC 61131-3 virtual machine run-time.  More specifically, I have considering what form the debugger client and interface protocol might take – While one approach might be to start work on a development environment (or build upon an existing platform such as GEB Automation Integrated Development Environment [IDE],, the scope of such development extends far beyond the core focus on this project.  Such an extension of scope is neither desirable with respect to ensuring my own on-going interest in this project (which as already grown beyond my initial expectations of development scope) and overall project quality.

Beyond the development or debugging environment, there is also a question as to what communication protocol should be employed for debugging between the development environment and the IEC 61131-3 virtual machine run-time running on the target hardware.  With a desire to ensure the interoperability of this platform, my preference would be for a published standard or protocol, however none of the existing, standard industrial protocols (with which I have experience), incorporate sufficient scope to necessarily support all operations required for debugging of IEC 61131-3 applications – such as start application, stop application, step execution, continue execution and the setting and/or clearing of breakpoints.  Moreover, Google searches for “debugger protocols” returned links to protocols better suited to more capable host environments than those where I would expect the IEC 61131-3 virtual machine run-time to be executed.

Nevertheless, after having spent some time considering available options for remote debugging, an interesting idea emerged – Why not use the GNU Debugger (gdb, for debugging applications running on the IEC 61131-3 virtual machine run-time?

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