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Add emscripten guards to shared_library.c's dlopen path - #591
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Tobias-Fischer wants to merge 1 commit into
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Add emscripten guards to shared_library.c's dlopen path#591Tobias-Fischer wants to merge 1 commit into
Tobias-Fischer wants to merge 1 commit into
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Two related gaps in rcutils_load_shared_library() / rcutils_get_platform_library_name(),
found while getting rcl_logging_implementation's dlopen-by-name backend
selection working on emscripten-wasm32:
- rcutils_get_platform_library_name() had no emscripten branch, so it always
fell through with written == 0 ("failed to format library name"),
regardless of which RCL_LOGGING_IMPLEMENTATION backend was requested.
wasm32 side modules use the same "lib<name>.so" convention as Linux.
- The post-dlopen path-resolution code took the _GNU_SOURCE branch (which
emscripten's headers define) and called dlinfo(..., RTLD_DI_LINKMAP, ...).
Emscripten's dlopen()/dlinfo() are a JS-backed shim, not glibc's, and
don't support reading back a real struct link_map -- so a successful
dlopen() got treated as a failure once dlinfo() returned -1. The #else
branch (reuse the path dlopen() was given) already covers this platform
correctly.
Verified end-to-end on a ROS 2 rolling + rmw_zenoh_pico + real-pthreads
emscripten-wasm32 build: a wasm32 rclpy talker's logging initialization
(rcl_logging_configure -> rcl_logging_implementation -> this dlopen path)
now succeeds instead of aborting with "failed to load any logging
implementations".
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>Tobias-Fischer added a commit
to Tobias-Fischer/ros-rolling
that referenced
this pull request
Sep 9, 2026
- Bump the vinca pin to 325d0af, which also sets CMAKE_SHARED_MODULE_CREATE_C/CXX_FLAGS (not just the SHARED-library variants) -- CMake's MODULE library type, used by pybind11_add_module() for every Python C extension (rclpy's own _rclpy_pybind11, and each message package's rosidl_generator_py typesupport accessor), was linking without USE_PTHREADS=1 even though its objects compiled with atomics fine, producing a load-time "mismatch in shared state of memory" next to the rest of a pthreads build. Invisible until something used pybind11_add_module() -- found getting a live rclpy demo running. - Add two Emscripten guards to patch/ros-rolling-rcutils.emscripten.patch (upstreamed as ros2/rcutils#591) so rcl_logging_implementation's dlopen-by-name backend selection works: rcutils_get_platform_library_name() had no emscripten case (always "failed to format library name"), and the post-dlopen path resolution took a dlinfo(RTLD_DI_LINKMAP) branch that Emscripten's JS-backed dlopen doesn't support, treating a successful dlopen() as a failure. - Document a known gap (see pixi.toml comment): rosidl_typesupport_ microxrcedds_cpp's codegen doesn't handle service "_Event" messages, so action_msgs/lifecycle_msgs/rcl_interfaces/rosgraph_msgs/statistics_msgs/ type_description_interfaces/micro_ros_msgs need a second, C-only rebuild pass rather than the global STATIC_ROSIDL_TYPESUPPORT_CPP override this task sets -- a real rclpy talker (not just rclc) verified end-to-end through this same rmw_zenoh_pico pipeline surfaced this. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
4 tasks
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Summary
Two related gaps in
rcutils_load_shared_library()/rcutils_get_platform_library_name(), found while gettingrcl_logging_implementation's dlopen-by-name backend selection working onemscripten-wasm32:rcutils_get_platform_library_name()had no emscripten branch, so it always fell through withwritten == 0("failed to format library name"), regardless of whichRCL_LOGGING_IMPLEMENTATIONbackend was requested. wasm32 side modules use the samelib<name>.sonaming convention as Linux, so this reuses that branch.dlopen()path-resolution code took the_GNU_SOURCEbranch (which emscripten's headers define) and calleddlinfo(..., RTLD_DI_LINKMAP, ...). Emscripten'sdlopen()/dlinfo()are a JS-backed shim, not glibc's, and don't support reading back a realstruct link_map— so a successfuldlopen()was getting treated as a failure oncedlinfo()returned -1. The#elsebranch (reuse the pathdlopen()was given) already covers this platform correctly, so this just excludes emscripten from the glibc-specific branch above it.Both are narrow, additive
#if/#elifguard changes — no behavior change on any existing platform.Test plan
Verified end-to-end on a ROS 2 rolling +
rmw_zenoh_pico+ real-pthreadsemscripten-wasm32build (companion work in RoboStack/vinca#154 and RoboStack/ros-rolling#46): a wasm32rclpytalker's logging initialization (rcl_logging_configure→rcl_logging_implementation→ this dlopen path) now succeeds instead of aborting with "failed to load any logging implementations", regardless of which backend (rcl_logging_spdlogorrcl_logging_noop) is selected.Full write-up
All the changes this required, across every repo, are documented together in Tobias-Fischer/ros2-emscripten-zenoh-demo — including a working
rclcandrclpybrowser demo verified end-to-end against a nativezenohdrouter.🤖 Generated with Claude Code