CONFIG_DEBUG_OPTIMIZATIONS does not allow setting breakpoints anywhere

Question

When debugging the exercise 1 application from `Lesson 2 – Reading buttons and controlling LEDs` of `nRF Connect SDK Fundamentals`, I cannot set a breakpoint wherever I want. 
 Somehow it is either not picked up or it gets picked the line below. 
 However, if I debug step by step from the beginning, it can stop on all lines. 
 In this code: 
 
 The 2 lines below get ignored, I cannot break on them: 
 
 I am setting CONFIG_DEBUG_OPTIMIZATIONS by selecting: 
 
 However, it seems not sufficient as there are probably some optimisations that are made on the code. 
 I remember when debugging on nRF52, I had to set: 
 
 so `-O0 -g3` flags in order to propely debug and I think I need to also enable `CONFIG_NO_OPTIMIZATIONS` but I can't override its value together with `CONFIG_DEBUG_OPTIMIZATIONS`. 
 
 Another issue I see is if I put a breakpoint here just before starting to debug: 
 
 I get the debugger to stop here: 
 
 Any hints?

Kristian R · Answer

This should be solvable by disabling optimizations. 
 If you are using the nRF Connect for VSCode extension, edit the build configuration: 
 
 and set it to debug mode, but also add the CMake arg here: -DCONFIG_NO_OPTIMIZATIONS=y 
 
 and click the blue button ( important !). 
 
 As for why the debugger is stopping you in the TFM file, it is because that file's debug info (build/blinky/tfm/bin/tfm_s.elf) is being added as an extra symbol-file to GDB, in addition to zephyr.elf, and this file is also named main.c . 
 If you keep clicking Continue (F5) on the debugger, you should eventually hit the actual src/main.c file you want. 
 I will investigate if that can be improved 
 
 Best regards, 
 Kristian from the nRF Connect for VSCode developer team