**undefined symbol** ERROR

[kailiangshang]

when i use official docker file and run command docker run -it --rm my/ros:aptgetter

Dockerfile

FROM ros:rolling-ros-core as aptgetter \
RUN apt-get update && apt-get install -y \
ros-${ROS_DISTRO}-demo-nodes-cpp \
ros-${ROS_DISTRO}-demo-nodes-py && \
rm -rf /var/lib/apt/lists/*

CMD ["ros2", "launch", "demo_nodes_cpp", "talker_listener_launch.py"]

I get an error
[talker-1] /opt/ros/rolling/lib/demo_nodes_cpp/talker: symbol lookup error: /opt/ros/rolling/lib/demo_nodes_cpp/talker: undefined symbol: rcutils_strnlen
[listener-2] /opt/ros/rolling/lib/demo_nodes_cpp/listener: symbol lookup error: /opt/ros/rolling/lib/demo_nodes_cpp/listener: undefined symbol: rcutils_strnlen

Can you help me solve this problem, thanks

[ruffsl]

Hmm, indeed I can locally reproduce the issue as well. Thanks for reporting, @kailiangshang !

Details

> cat Dockerfile 
FROM ros:rolling-ros-core as aptgetter

# install ros package
RUN apt-get update && apt-get install -y \
      ros-${ROS_DISTRO}-demo-nodes-cpp \
      ros-${ROS_DISTRO}-demo-nodes-py && \
    rm -rf /var/lib/apt/lists/*

# launch ros package
CMD ["ros2", "launch", "demo_nodes_cpp", "talker_listener_launch.py"]

> docker build -t my/ros:aptgetter .
[+] Building 22.4s (6/6) FINISHED                                                                                                                                                                                            docker:default
 => [internal] load build definition from Dockerfile                                                                                                                                                                                   0.0s
 => => transferring dockerfile: 352B                                                                                                                                                                                                   0.0s
 => WARN: FromAsCasing: 'as' and 'FROM' keywords' casing do not match (line 1)                                                                                                                                                         0.0s
 => [internal] load metadata for docker.io/library/ros:rolling-ros-core                                                                                                                                                                1.0s
 => [internal] load .dockerignore                                                                                                                                                                                                      0.0s
 => => transferring context: 2B                                                                                                                                                                                                        0.0s
 => [1/2] FROM docker.io/library/ros:rolling-ros-core@sha256:f91e52d47cd8868c080eb5fd7cdce5b870aeac6e8e2cbec5d58b9fa9b66333a4                                                                                                         15.6s
 => => resolve docker.io/library/ros:rolling-ros-core@sha256:f91e52d47cd8868c080eb5fd7cdce5b870aeac6e8e2cbec5d58b9fa9b66333a4                                                                                                          0.0s
 => => sha256:b8859fd1c03008461caedfbbd537a9fe76de00a8f519ffebc5f73a9dad352c20 2.13kB / 2.13kB                                                                                                                                         0.0s
 => => sha256:ecc42fb010ae069e75183b2188d2e54e66661c8747be3a9342eab35839fbfa4c 3.84kB / 3.84kB                                                                                                                                         0.0s
 => => sha256:e67f8fffa6a0513fb6ef892fef2b2e590c91a0efc43aecbc0056c64b953a5ba2 683.81kB / 683.81kB                                                                                                                                     0.5s
 => => sha256:4ffabbe26c08113807e06f69850fffddff4c094da296c84200dfba20bf8b00a1 6.75MB / 6.75MB                                                                                                                                         0.5s
 => => sha256:32f112e3802cadcab3543160f4d2aa607b3cc1c62140d57b4f5441384f40e927 29.72MB / 29.72MB                                                                                                                                       0.7s
 => => sha256:f91e52d47cd8868c080eb5fd7cdce5b870aeac6e8e2cbec5d58b9fa9b66333a4 2.67kB / 2.67kB                                                                                                                                         0.0s
 => => sha256:00a6eb2026e3ba404ffc1574443c8dc7cf106d106758a2d11c8d8a47d6626ac9 94.04kB / 94.04kB                                                                                                                                       0.7s
 => => sha256:9a47e5e2434a12c5993482eb113554ce547d06c88d2798f04f429f906c0c7398 132.41MB / 132.41MB                                                                                                                                     3.2s
 => => sha256:7ef12497fa909ef4895e929530351af3557fa3501ef16c1a8f6ee8561d93f6ac 195B / 195B                                                                                                                                             0.9s
 => => extracting sha256:32f112e3802cadcab3543160f4d2aa607b3cc1c62140d57b4f5441384f40e927                                                                                                                                              2.3s
 => => extracting sha256:e67f8fffa6a0513fb6ef892fef2b2e590c91a0efc43aecbc0056c64b953a5ba2                                                                                                                                              0.2s
 => => extracting sha256:4ffabbe26c08113807e06f69850fffddff4c094da296c84200dfba20bf8b00a1                                                                                                                                              0.5s
 => => extracting sha256:00a6eb2026e3ba404ffc1574443c8dc7cf106d106758a2d11c8d8a47d6626ac9                                                                                                                                              0.0s
 => => extracting sha256:9a47e5e2434a12c5993482eb113554ce547d06c88d2798f04f429f906c0c7398                                                                                                                                             10.9s
 => => extracting sha256:7ef12497fa909ef4895e929530351af3557fa3501ef16c1a8f6ee8561d93f6ac                                                                                                                                              0.0s
 => [2/2] RUN apt-get update && apt-get install -y       ros-rolling-demo-nodes-cpp       ros-rolling-demo-nodes-py &&     rm -rf /var/lib/apt/lists/*                                                                                 5.2s
 => exporting to image                                                                                                                                                                                                                 0.3s 
 => => exporting layers                                                                                                                                                                                                                0.2s 
 => => writing image sha256:b1517adc5c87667596798c647196967ffd0965a56640a8ab9d24752f6b18064c                                                                                                                                           0.0s 
 => => naming to docker.io/my/ros:aptgetter                                                                                                                                                                                            0.0s 
                                                                                                                                                                                                                                            
 1 warning found (use docker --debug to expand):                                                                                                                                                                                            
 - FromAsCasing: 'as' and 'FROM' keywords' casing do not match (line 1)

> docker run -it --rm my/ros:aptgetter
[INFO] [launch]: All log files can be found below /root/.ros/log/2025-07-24-18-12-36-984348-e5e354e8d00c-1
[INFO] [launch]: Default logging verbosity is set to INFO
[INFO] [talker-1]: process started with pid [18]
[INFO] [listener-2]: process started with pid [19]
[listener-2] /opt/ros/rolling/lib/demo_nodes_cpp/listener: symbol lookup error: /opt/ros/rolling/lib/demo_nodes_cpp/listener: undefined symbol: rcutils_strnlen
[talker-1] /opt/ros/rolling/lib/demo_nodes_cpp/talker: symbol lookup error: /opt/ros/rolling/lib/demo_nodes_cpp/talker: undefined symbol: rcutils_strnlen
[ERROR] [listener-2]: process has died [pid 19, exit code 127, cmd '/opt/ros/rolling/lib/demo_nodes_cpp/listener --ros-args'].
[ERROR] [talker-1]: process has died [pid 18, exit code 127, cmd '/opt/ros/rolling/lib/demo_nodes_cpp/talker --ros-args'].

I suspect this is a recent regression in upstream packaging of the demo packages, or specifically in dependency management, as when manually including the rcutils to install and rebuilding, the demo then works as expected.

# install ros package
RUN apt-get update && apt-get install -y \
+      ros-${ROS_DISTRO}-rcutils \
      ros-${ROS_DISTRO}-demo-nodes-cpp \
      ros-${ROS_DISTRO}-demo-nodes-py && \
    rm -rf /var/lib/apt/lists/*

> docker run -it --rm my/ros:aptgetter
[INFO] [launch]: All log files can be found below /root/.ros/log/2025-07-24-18-20-00-136009-b6485f5e6846-1
[INFO] [launch]: Default logging verbosity is set to INFO
[INFO] [talker-1]: process started with pid [18]
[INFO] [listener-2]: process started with pid [19]
[talker-1] [INFO] [1753381201.253325598] [talker]: Publishing: 'Hello World: 1'
[listener-2] [INFO] [1753381201.253962147] [listener]: I heard: [Hello World: 1]
[talker-1] [INFO] [1753381202.253425854] [talker]: Publishing: 'Hello World: 2'
[listener-2] [INFO] [1753381202.253994040] [listener]: I heard: [Hello World: 2]

I say recent, as I recall this working fine for rolling when submitting the PR to update the docs for this example:

• [ROS] Update Official Docker image docs docker-library/docs#2578

Although, from the git blame for demo_nodes_cpp, it doesn't seem like anything meaningful has changed in the demos:

https://github.com/ros2/demos/blob/1deab0003220323ae93bb90b3fd8913c265beec7/demo_nodes_cpp/package.xml#L38

So, I'd assume this is particular to rcutils, but only for rolling as the Dockerfile still works as expected using kilted:

-FROM ros:rolling-ros-core as aptgetter
+FROM ros:kilted-ros-core as aptgetter

CC @nuclearsandwich @ahcorde @mikaelarguedas @clalancette

Edit: Related

• use strnlen_s instead of strnlen if available ros2/rcutils#430
• Undefined reference to rcutils_strnlen ros2/rcutils#503

CC @razr @fujitatomoya @christophfroehlich

[clalancette]

Yes, this is almost certainly from ros2/rcutils#430 . This has already been released as version 7.0.0, and synced, so probably the docker image needs to be rebuilt.

[ruffsl]

Curious, why didn't the demo deb packages built with recent ABI change not force apt to download/install rcutils v7?

[clalancette]

Curious, why didn't the demo deb packages built with recent ABI change not force apt to download/install rcutils v7?

On the buildfarm, when a package gets rebuilt, everything that depends on it (recursively) also gets rebuilt. In this case, it means that when rcutils got rebuilt to 7.0.0, demo_nodes_cpp almost certainly got rebuilt as well.

However, there are some additional steps in there. First, demo_nodes_cpp may have failed to rebuild, though that seems not to be the case. Second, it is possible that it didn't get pulled in during the last sync: https://discourse.openrobotics.org/t/new-packages-for-ros-2-rolling-ridley-2025-07-16/45254 . And actually, that seems to be what happened. ros-rolling-rcutils was bumped to 7.0.0, but there is no corresponding update to ros-rolling-demo-nodes-cpp. I'm not quite sure why that happened, but FYI @Yadunund . It might be worthwhile to do another Rolling sync "soon" to try and fix this up.

[kailiangshang]

@ruffsl Thanks！

[kailiangshang]

@clalancette Tag me if anything comes up. Cheers!

[ruffsl]

And actually, that seems to be what happened. ros-rolling-rcutils was bumped to 7.0.0, but there is no corresponding update to ros-rolling-demo-nodes-cpp.

@clalancette , I'm not sure I follow. Why then would my rcutils Dockerfile change above resolve the missing symbols?

Given explicitly apt installing rcutils updates the package to v7, as seen when inspecting the image before and after my change, it would seem that the current demo nodes (also note timestamps) where already built against the newer ABI:

> docker run -it --rm my/ros:aptgetter-before apt list -a "ros-rolling-demo-*"
Listing... Done
ros-rolling-demo-nodes-cpp/now 0.37.1-1noble.20250701.223550 amd64 [installed,local]

ros-rolling-demo-nodes-py/now 0.37.1-1noble.20250701.214615 amd64 [installed,local]

> docker run -it --rm my/ros:aptgetter-before apt list -a "ros-rolling-*" > before
> docker run -it --rm my/ros:aptgetter-after apt list -a "ros-rolling-*" > after
> diff before after 
172c172
< ros-rolling-rcutils/now 6.10.1-1noble.20250620.173646 amd64 [installed,local]
---
> ros-rolling-rcutils/now 7.0.0-1noble.20250701.191104 amd64 [installed,local]

I understand layers in the ros:rolling-ros-core base image are stale with rcutils v6.10.1 pre-installed, facilitating this ABI mismatch. However, why didn't installing demo-nodes v0.37.1-1noble.20250701.223550 not transitively cause apt to update rcutils to v7.0.0, particularly given the major semantic version bump in a library dependency? Does Bloom not capture that degree of semantic version compatibility when packaging Debian metadata?

Edit:

Odd... It seems no semantic version constraints are embedded in the debian package for any ROS related dependency?

> docker run -it --rm my/ros:aptgetter-before apt show "ros-rolling-demo-nodes-cpp"
Package: ros-rolling-demo-nodes-cpp
Version: 0.37.1-1noble.20250701.223550
Status: install ok installed
Priority: optional
Section: misc
Maintainer: Aditya Pande <aditya.pande@openrobotics.org>
Installed-Size: 7165 kB
Depends: libc6 (>= 2.34), libconsole-bridge1.0 (>= 1.0.1+dfsg2), libgcc-s1 (>= 3.3.1), libstdc++6 (>= 13.1), ros-rolling-example-interfaces, ros-rolling-launch-ros, ros-rolling-launch-xml, ros-rolling-rcl, ros-rolling-rcl-interfaces, ros-rolling-rclcpp, ros-rolling-rclcpp-components, ros-rolling-rcpputils, ros-rolling-rcutils, ros-rolling-rmw, ros-rolling-std-msgs, ros-rolling-ros-workspace
Download-Size: unknown
APT-Manual-Installed: yes
APT-Sources: /var/lib/dpkg/status
Description: C++ nodes which were previously in the ros2/examples repository but are now just used for demo purposes.

[clalancette]

Odd... It seems no semantic version constraints are embedded in the debian package for any ROS related dependency?

Correct. This isn't a common problem, so we don't actually put version constraints. While we could do it, it would actually be hard to keep up-to-date.

[nuclearsandwich]

However, why didn't installing demo-nodes v0.37.1-1noble.20250701.223550 not transitively cause apt to update rcutils to v7.0.0, particularly given the major semantic version bump in a library dependency? Does Bloom not capture that degree of semantic version compatibility when packaging Debian metadata?

As surmised and confirmed by @clalancette version constraints from package.xml are not actually considered by bloom nor downstream processes. I think ros-infrastructure/bloom#455 captures most of why this is not an easy thing to make generally work or make work on the buildfarm which embeds timestamps into the package versions.

We rely instead on:

1. syncs have to be manually triggered
2. the expectation that the ROS boss is checking for a coherent state before publishing a sync to main
3. apt dist-upgrade or equivalent is performed before adding or removing ROS packages

The first two are managed by the ROS team but the final one is an expectation on the ROS users which is why it's the hardest to rely on.