Hi, I've gone thru the setup for using gdb with a Teensy 4.1. I am able to set breakpoints before Start Debugging or when at a breakpoint that I set initially.
 
However, once the app is running my attempts to set a breakpoint fail. I get a red outline circle containing a yellow warning exclamation point in the left hand column, with the following mouse-over message

"The breakpoint will not be hit. Attempting to bind the breakpoint ..." followed by file and line number

I tried Break All in the hopes that would allow me to set additional breakpoints. Unfortunately that hard locks Visual Studio 2022 and have to kill it with Task Manager.

Any suggestions would be appreciated.

thanks,
steve

Confirmed Optimize:Debug. I attached a screen shot of those settings.

I get the same results with No Project + Libraries Optimization.

I see that I failed to provide the key detail about landing on breakpoints in my initial post. I am able to land on breakpoints that I set before upload. I can also land on new breakpoints that I set while execution is stopped at an existing breakpoint. I am able to do the usual debugging suspects (e.g. single step, watch variables) when at a breakpoint. 

My problems occur only when the program is executing. I cannot set new breakpoints or use Break All to stop execution.

Thanks for that key piece of information. I want more control than breaking at the top of the loop every time. I connected a button to the Teensy that triggers an otherwise unused code path with a breakpoint in it. This allows me to break into the debugger on demand.

I'm still running newer versions of Arduino and Teensyduino than the know stable you mentioned previously.  With the newer versions I'm noticing a couple of things.

The sample code includes this line:
 

while (!SerialUSB1) {}    // Wait for Debugger connect  

Most of the time SerialUSB1 never becomes true. If I comment out the while loop and use the local board.txt from your setup instructions that delays the debugger attach, gdb connects reliably.

The other thing I'm noticing is that single stepping is flaky. Sometimes it works. Sometimes execution continues without stopping on the next line. Sometimes gdb exits. 

I've added experimenting with the know stable versions to my todo list.