3DS debugging


  • 3DS

    You should have the Homebrew Launcher installed on your 3DS. See Emulation on 3DS for more information.

  • PC

    You either need Docker (recommended) or devkitARM installed on your PC

Run .3dsx files remotely

  1. Connect 3dslink

    1. Make sure the 3DS is connected to your local network via Wifi

    2. On the 3DS, open HomeBrew Launcher and press Y

    3. Note the IP address

  2. Start the application remotely

    1. On a PC, open a terminal and change to the directory containing the .3dsx file you would like to debug

    2. Run this command

      docker run --rm -v "$PWD:/build" --network=host devkitpro/devkitarm 3dslink /build/retroarch_3ds.3dsx

      (Change retroarch_3ds.3dsx with the name of the application)

      If you see this error:

      No response from 3DS!

      Try again with the IP address of the 3DS, e.g.

      docker run --rm -v "$PWD:/build" --network=host devkitpro/devkitarm 3dslink /build/retroarch_3ds.3dsx -a

Run .cia files remotely


  1. On a PC, download this file: https://raw.githubusercontent.com/Steveice10/FBI/master/servefiles/servefiles.py

  2. On the 3DS, open FBI and go to Remote Install > Receive URLs over the network

  3. Send the file from the PC

    python /path/to/servefiles.py FILE.cia

    (Replace /path/to/servefiles.py with the path to servefiles.py, with the IP of the 3DS, and FILE.cia with the CIA file to install)

  4. On the 3DS, press A to confirm the remote install


  1. Compile the application you wish to debug with debug symbols enabled

    You can check the file after compiling if you’re not sure:

    $ file retroarch_3ds.elf
    retroarch_3ds.elf: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), statically linked, with debug_info, not stripped
  2. Set up the application you wish to debug

    • To debug .cia files, install the file on the 3DS using FBI
      • You can also use FBI to install the .cia file remotely using the instructions above
    • (Not recommended) To debug .3dsx files, simply open the Homebrew Launcher and then press home to return to the home screen

      ⚠ Unfortunately this isn’t recommended as the application doesn’t seem to exit cleanly when done debugging

  3. Enable debugging on the 3DS

    1. On the 3DS, go to the main menu and press L+down+Select to bring up the Rosalina menu

    2. Go to Debugger options > Enable debugger

    3. Then go to Force-debug next application at launch

    4. Make note of the IP address and port

    5. Exit Rosalina menu (pres B)

  4. Start the application you wish to debug

    • To debug a .cia file that has already been installed, simply start the application from the 3DS home screen
    • To debug a .3dsx file, re-open Homebrew Launcher by pressing home and then use the instructions above to run the file remotely
  5. On your PC, start gdb and connect to the 3DS

    1. Start the container with the workaround for https://github.com/devkitPro/docker/issues/24

      docker run -it --rm -v "$PWD:/build" devkitpro/devkitarm sh -c "PATH=/opt/devkitpro/devkitARM/bin:"$PATH"; apt -y install libpython2.7 libtinfo5; bash"
    2. Start the debugger and connect to the 3DS, e.g.

      cd /build
      arm-none-eabi-gdb retroarch_3ds.elf
      (gdb) target remote

      (Replace IP and port with the ones you made a note of earlier)

    3. Start debugging

      1. Set a breakpoint, e.g.

        (gdb) b nameoffunction
      2. Continue until next breakpoint:

        (gdb) c

      Some helpful gdb commands:

      • n - Go line-by-line without stepping into functions
      • s - Go line-by-line and step into functions
      • p - Print the value of a variable, e.g.

        (gdb) p g_defaults.dirs[DEFAULT_DIR_ASSETS]
        $6 = "sdmc:/retroarch/assets"
      • finish - Go until the end of the current function
      • d - Delete all breakpoints

      To break while running (to insert a new breakpoint, etc), press Ctrl+C