mpaland-printf leads to broken output with GCC 9.3.1

[morigawa]

Description

Using gcc 9.3.1 mpaland-printf breaks the output on the nrf52840dk. (e.g. hello-world example).
Changing to gcc 10.3.1 fixed the problem, but I assumed RIOT does support gcc 8+. Introduced was this issue in #21438, where the mpaland-printf package was added as dependency. Since this PR was merged, the output is broken. Adding that pkg manually to a makefile has the same effect at an older state.

Expected results

Without mpaland-printf:

2025-11-03 12:47:06,165 # main(): This is RIOT! (Version: 2025.10-devel-168-g2ed57-HEAD)
2025-11-03 12:47:06,165 # Hello World!
2025-11-03 12:47:06,170 # You are running RIOT on a(n) nrf52840dk board.
2025-11-03 12:47:06,173 # This board features a(n) nrf52 CPU.

Actual results

With mpaland-printf:

2025-11-03 12:47:49,442 # � � � � � � � � � � � � � �ou are running RIOT on a(n) nrf52840dk board.
2025-11-03 12:47:49,444 # This board features a(n) nrf52 CPU.

Versions

• Operating System: "Ubuntu" "22.04.5 LTS (Jammy Jellyfish)"
• arm-none-eabi-gcc: arm-none-eabi-gcc (GNU Arm Embedded Toolchain 9-2020-q2-update) 9.3.1 20200408 (release)
• clang: Ubuntu clang version 14.0.0-1ubuntu1.1

[mguetschow]

Maybe @maribu might have an idea what could cause this?

[maribu]

Interesting. I would suspect that the way we wrap the stdio functions to mpaland-printf on newlib not working with the used version of newlib.

Could you provide a docker container that contains the toolchain that builds the broken binary, so that I can reproduce the issue and test a potential fix with it?

If not, could you provide the ELF file that is affected (with debug symbols)?

[crasbe]

It was actually surprisingly difficult to get such an old version of GCC running. I did not find a package for it in the Launchpad, so I used the package from 20.04 Focal.

Dockerfile:

# Base image: Ubuntu 22.04 (Jammy Jellyfish)
FROM ubuntu:jammy

# Avoid interactive prompts during package installation
ENV DEBIAN_FRONTEND=noninteractive

# Update system and install required packages
RUN apt-get update && \
    apt-get install -y --no-install-recommends \
        ca-certificates \
        build-essential \
        libnewlib-arm-none-eabi \
        make \
        gcc-multilib \
        python3-serial \
        python3-psutil \
        wget \
        curl \
        unzip \
        git \
        openocd \
        gdb-multiarch \
        binutils-arm-none-eabi && \
    # Clean up to reduce image size
    apt-get clean && \
    rm -rf /var/lib/apt/lists/*

RUN wget http://launchpadlibrarian.net/465590960/libisl22_0.22.1-1_amd64.deb
RUN wget http://launchpadlibrarian.net/468792405/gcc-arm-none-eabi_9-2019-q4-0ubuntu1_amd64.deb

RUN dpkg -i libisl22_0.22.1-1_amd64.deb
RUN dpkg -i gcc-arm-none-eabi_9-2019-q4-0ubuntu1_amd64.deb

# Set a default working directory
WORKDIR /workspace

RUN git clone https://github.com/RIOT-OS/RIOT

# Default command when starting the container
CMD ["/bin/bash"]

buechse@skyleaf:~/RIOTstuff/docker-mpaland$ docker build -t docker-mpaland .
...

buechse@skyleaf:~/RIOTstuff/docker-mpaland$ docker run -it docker-mpaland
root@5e81085e03ce:/workspace# ls
RIOT
root@5e81085e03ce:/workspace# arm-none-eabi-gcc --version
arm-none-eabi-gcc (15:9-2019-q4-0ubuntu1) 9.2.1 20191025 (release) [ARM/arm-9-branch revision 277599]
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

root@5e81085e03ce:/workspace#

Edit: had to update it to include newlib.

[crasbe]

I had to update the Dockerfile to include newlib so it actually builds:

root@6ae9012a2c0d:/workspace/RIOT# BOARD=nrf52840dk make -C examples/basic/hello-world/ -j
make: Entering directory '/workspace/RIOT/examples/basic/hello-world'
Building application "hello-world" for "nrf52840dk" with CPU "nrf52".

"make" -C /workspace/RIOT/pkg/cmsis/
"make" -C /workspace/RIOT/pkg/mpaland-printf/
"make" -C /workspace/RIOT/build/pkg/mpaland-printf -f /workspace/RIOT/pkg/mpaland-printf/mpaland-printf.mk
...
"make" -C /workspace/RIOT/cpu/nrf5x_common/periph
   text    data     bss     dec     hex filename
   6940       0    2320    9260    242c /workspace/RIOT/examples/basic/hello-world/bin/nrf52840dk/hello-world.elf
make: Leaving directory '/workspace/RIOT/examples/basic/hello-world'