As I mentioned up on the PJRC forum thread: 
https://forum.pjrc.com/threads/58979-duplicate-Arduino-Debug-via-Serial?p=244482...

I thought I would try out the new GDBStub stuff, with an sketch I have been working on that controls a Lynxmotion Hexapod with their LSS servos, using my own T4.1 board.  I am also using the Teensy USB Host support to allow me to control the hexapod using BlueTooth Joysticks, currently mainly a PS3.

I am now able to build using @ftrias setup on Teensudino and start up the sketch. 

But it would be a lot easier to debug at the Source level so I update my VisualMicro on VS2019, with the appropriate install.  I setup for dual Serial, I set to debug , 
No optimize sketch-library, Debug Hardware GDBStub.

I also setup to show hidden files, so I can now see the libraries, which is great. 

But now when I compile the link fails: 

LSS_Phoenix_Input_USB_Joystick.cpp.o: In function USBDriver::USBDriver()

Error linking for board Teensy 4.1
USBHost_t36.h:429: undefined reference to vtable for USBDriver
Build failed for project 'LSS_PhoenixUSBJoystick'

LSS_Phoenix_Input_USB_Joystick.cpp.o: In function USBHIDInput::USBHIDInput()
USBHost_t36.h:505: undefined reference to vtable for USBHIDInput

collect2.exe*: error: ld returned 1 exit status

  

Again it links and run using arduino, so wondering what options that I may need to do to compile the sketch and this library to make it such that it will properly link in debug mode. 

The sketch is up in the github project: https://github.com/KurtE/LSS_Test_sketches/tree/master/LSS_PhoenixUSBJoystick

I have not uploaded the VS (Or the Sublime text) projects. 

Thanks, 

I notice two different issues with my stuff here.  First off it appears like the code is choosing the version of the library that is installed by Teensyduino In my case (C:\arduino-1.8.13\hardware\teensy\avr\libraries\USBHost_t36) instead of my WIP version of the library which is stored in my <Sketch folders>/libraries/... again in my case: C:\Users\kurte\Documents\Arduino\libraries\USBHost_t36

Note: I am also playing a trick here where the actual sources are in my d:\github\USBHost_t36 directory and my library folder (Windows 10) is using a directory Symbolic link to it... 

But hopefully there is some simple parameter in the project that will point it to the right place... 

But when I switch over to default optimizations (Faster) and switch to Default Optimization, it still fails to link. 

I included the text file showing the log. If you search for some of the files contained in the file like bluetooth.cpp, you will see that the compile has both an -O2 at start of the compile and later near end of command line it also has an -O0.

I believe that it has to do with the some of the Extras stuff that is shown at start of build like:

build.vm.extra_flags.core=-O0
build.vm.extra_flags.library=-O0
build.vm.extra_flags.project=-O0 

Hopefully I can find some place in some configuration and just remove these? 

Quick update - I completely deleted everything but the original code (all stuff created by VisualStduio...)  Then restarted, and told it to use an existing Arduino project...   
I have not turn on your debugger settings yet.  but it does now link  

But as mentioned it does use the version of USBHost_t36 that was installed with Teensyduino. As is in the compile lines that include: 

-I"C:\arduino-1.8.13\hardware\teensy\avr\libraries\USBHost_t36"

Not sure what would happen if I now simply delete it from there...   
It fails until I tell the system to rescan libraries... Now it looks like it builds...

Now to see if I can turn on debug with this one...

Great thanks. We will look into library priority. Historically the sketchbook/libraries is weak and does not allow a different library for different architectures. Therefore libraries includes below each architecure are consider to be of higher importance, leaving the sketchbook\libraries to cater for any architecure that does not provide the library.

That said, it should be an option so that it can do same as Arduino IDE.

You can do exactly as you have said, delete the one you don't want then click "Rescan" in Visual Micro or restart the IDE.

After you do that all should be well, however you can also use the "create shared project when adding libraries" option on the "Add Library" menu. After enabled that checkbox reselect the library from the "Add Library" menu. This will link the live library sources to the solution as a Visual Studio shared c++ project. It will also add a Reference from the Arduino project to the library. You will see all this in the solution explorer. With this configuration Visual Micro will know to use the library in the sketchbook\libraries folder even if the one below the Teensy core platform is subsequently replaced/updated/reinstated.

Adding the library as a shared project will show how easily you can add libraries of a "specific" location. This is useful if you want your libraries to be stored in more flexible locations than the published Arduino locations. There is also a new Arduino library project in "File>New>Project" which shows more detail of shared library projects.

Quick updates:

I have been able to make some of this work, found I had the best luck by doing the build and upload like and then attach the debug process... 

But again there are a few things I have not figured out the proper way of doing things like:

a) After I connect the debugger, can I break back in to the program to debug?  If I do the break-all, the Visual Studio (2019) hangs or at least the UI is unresponsive, and about the only thing I can do is kill the process

b) Can I while my program is running, set a new break point?  So far when I try it and I am not at a breakpoint, it does not take, but if I then tell it to build-download and attach again it does... I assume that is normal.  Not a problem if I can break in... Maybe I will add a UI way to call the debugger... 

c) The GDBStub code has some other things to his stub, that you can supposedly call from command line GDB, like:
"monitor digitalWrite(13,1)"
Which would turn the LED on.   
Is there any way to feed a command line in to the GDB here? 

d) Should I raise an issue somewhere about your library search order code works different than Arduino?  As mentioned earlier, you use the one that Teensyduino installs, instead of my version in the Arduino sketches/libraries/... folder

e) Probably obvious, as I see you quickly do it in your video talking about this debugging, but how to open up Terminal window on the 2nd IO port.  That is I have the T4.1 configured Dual Serial, where COM32 is the GDB port (SerialUSB1) and 33 is the Serial port.  So I have COM32 selected and it compiles and uploads fine, I use the Attach to Process... Now I would like to open up terminal window on COM33.  What is best way to do this...  I can of course use different app, such as TyTerminal or Arduino Serial monitor, but just wondering...

Again thanks!

Thanks for the info. We are looking into a couple of things and will update with answers over the coming couple of days.

One minor point is that the "Other" tool bar button next to the serial monitor icon and "vMicro>General>Monitor Alternative" allow terminal to be opened on additional ports (unrelated to upload/debug)

Simon@Visual Micro wrote on Jul 6^th, 2020 at 6:58pm:

Thanks for the hints and web page.  I put a comment up on the PJRC forum with this.   I am having some fun.  Still running into a few pitfalls, but mostly work through them.  Things like how to stop the debugger.  Mostly I found I need to turn off the Teensy to get the Visual Studio out of a UI hang...  Likewise if I put a break in and then hit F10 it will not really ever let me back in... But the answer is: don't do that  

Thanks again

Simon@Visual Micro wrote on Jul 8^th, 2020 at 3:58pm:

Thanks for the information, yes the 2 comm port setup makes it a lot nicer. 

I am still trying to work my way through some of this stuff, like the boards.txt overrides. 

Also I thinking some of the issues I am running into is caused by the nature of the sketch I am trying to run.  In particular, it uses USB Host code, in this case on T4.1.  Also unclear at times what is best way to do things. 

Example: I put code in for joystick that if I press L3 button, it tries to break me into GDB.  I have tried both halt and the debug.setBreakpoint... Like:

#if defined(TEENSY_DEBUG_H)
			if (debug.isGDBConnected()) {
				DBGSerial.println(F("Trying to break in to GDB"));
				// lets try it through setting breakpoint at loop
				debug.setBreakpoint(&loop);
				//halt();
			}
			else
#endif 

And if I do this, once or twice it breaks in, usually by 3rd attempt it does not, although this last run appeared to allow it several times.  Setting the breakpoint like this does not appear to leave a breakpoint in the spot (loop) like yours does as if I hit F5 it does not continue to break there.  Also shows up different.  Shows up with RED X with Exception Unhandled (Trace/Breakpoint Trap) versus your normal breakpoint.  I can then set a normal breakpoint and it breaks each time I get to that location. 

Also with the setBreakpoint... Sometimes if I hit F10 it steps fine and other times it appears to go into never never land. 

But I maybe should also mention, that for example currently I have turned on debug printing in part of the USBHost code, in Bluetooth and Joystick code. And for example I am currently in a breakpoint and the Serial monitor continues to Spew out debug Serial prints from the Joystick and Bluetooth code, which is running due to Interrupts from the USB Host code.   One of the last runs, it crashed out of the debugger:

Again still just learning my way around