Unable to debug some code that uses C++ templates


When project is build with “debug” profile and GCC toolchain, I’m not able to debug some methods/functions, especially if they use C++ templates.

Example of project that has such issue: https://github.com/vznncv/mbed-os-issue-gcc-debug

This example contains method SimpleSequenceWrapper::next in the main.cpp with this issue:

  1. I’m not able to add breakpoint to some lines. When I try to add a breakpoint to line 154, the breakpoint is added to line 180 (method sin_wave_iter_t::next):

  2. Debugger doesn’t allow to “Step Into” SimpleSequenceWrapper::next method.


  • mbed-os version: 6.5.0
  • toolchain version: GNU Arm Embedded Toolchain 9-2020-q2-update
  • gdb server: pyocd
  • host: ubuntu 18.04 IDE: QtCreator


I’m able to “Step Into” SimpleSequenceWrapper::next method with “Operate by Instruction” mode:

When I run gdb command info list *<address> to map address to source code, I have noticed that
info list *<address> output differs from arm-none-eabi-addr2line
(command arm-none-eabi-addr2line -e BUILD/mbed-gcc-debug-demo.elf <address>):

program address gdb info list command output arm-none-eabi-addr2line output
0x800047a Line 121 of “…/main.cpp” starts at address 0x8000474 <SimpleSequenceWrapper<mbed::Callback<int ()> >::next(position_t const&)> and ends at 0x8000496 /home/vznncv/MyProjects/embedded-development/blackpill-projects/mbed-gcc-debug-demo/BUILD/…/main.cpp:125
0x8000492 Line 121 of “…/main.cpp” starts at address 0x8000474 <SimpleSequenceWrapper<mbed::Callback<int ()> >::next(position_t const&)> and ends at 0x8000496 /home/vznncv/MyProjects/embedded-development/blackpill-projects/mbed-gcc-debug-demo/BUILD/…/main.cpp:157
0x80004ea Line 331 of “/opt/gcc-arm-none-eabi/gcc-arm-none-eabi-9-2020-q2-update/arm-none-eabi/include/c++/9.3.1/chrono” starts at address 0x80004e4 /home/vznncv/MyProjects/embedded-development/blackpill-projects/mbed-gcc-debug-demo/BUILD/…/main.cpp:143

So the issue probably isn’t related with IDE, but is related with gdb that isn’t able to map program addresses to source code correctly.

Full gdb logs: https://github.com/vznncv/mbed-os-issue-gcc-debug/blob/master/docs/gdb_logs.txt


I have found that problem can be fixed if I change GCC flag from -Og to -O0.


Is it possible to fix debugging problem without default “debug” mbed-os profile modification/custom profile usage?