Hi, I'm running GDB on Teensy3.6 Dual Serial mode. I'm having problems with breakpoints when testing the TeensyDebug library example gdb.ino. I do have an additional variable being incremented in a FOR loop and a few arithmetic calculations. The problems appear to be related to optimization.

I've set Optimize: debug and also selected No Optimization, and also marked variables as volatile. The original example includes #pragma GCC optimize ("O0"), but this also doesn't seem to make any difference. Micro Build output is attached.

Here is why I think optimization is still occurring: breakpoints work on certain lines, but on others I get a message that the line does not exist due to compiler optimization. 

If I simply have a single breakpoint somewhere in the main loop(), watched variables increment correctly, but if I hover on the code statements when stopped at a breakpoint, certain variables have already been incremented before the incrementing line of code would be executed. 

Stepping causes the cursor position to cycle around lines that aren't in a loop, while watched variables that are in a loop elsewhere increment. 

I conclude that optimization probably isn't suppressed, and the execution arrows showing in VS don't match the lines where the execution is actually occurring.

Google suggests that gcc is known to ignore requests to suppress optimization. The workarounds people propose on StackOverflow  don't seem to have any effect here.

Am I overlooking something, or are there any suggestions?

Thx!!