CMake自定义目标显式调用bash却似乎使用sh？

Let me walk you through what's going wrong here and how to fix it, plus clean up a couple of bugs in your current create_ros_target function.

Why This Is Happening #

The core issue is xargs defaults to using /bin/sh to execute commands, even when you launch the parent process with bash -c. So when you pipe your setup scripts to xargs -r source, those source calls are running in a sh shell—not the bash you intended. That's why it looks like sh is being used.

On top of that, there's a bug in your target property lookup: you're assigning the dependency path to dep_path but then trying to use ${BUILD_PATH} (a non-existent variable) when building your ament_deps list.

Fixed Implementation #

Here's the corrected function, with explanations of the changes:

function(create_ros_target NAME DIR DEPENDENCIES)
    set(ament_deps "")
    foreach(dep ${DEPENDENCIES})
        # Fixed: Reference the loop variable ${dep} instead of literal "dep"
        get_target_property(dep_path ${dep} BUILD_PATH)
        # Add safety check to skip dependencies without a valid BUILD_PATH
        if(dep_path)
            list(APPEND ament_deps "${dep_path}/install/local_setup.bash")
        endif()
    endforeach()

    add_custom_target(${NAME} 
        COMMAND bash -c "
            # Source each setup script in bash (no xargs to avoid sh fallback)
            for setup_script in ${ament_deps}; do
                if [ -f \"\${setup_script}\" ]; then
                    source \"\${setup_script}\"
                fi
            done
            # Run ament build in the same bash context to preserve environment
            ament build --symlink-install ${DIR}
        "
        COMMENT "Building ROS target ${NAME} in directory ${DIR}"
    )

    # Complete your target properties here (your original code was cut off)
    # set_target_properties(${NAME} PROPERTIES ...)
endfunction()

Key Changes Made #

1. Fixed target property lookup: Changed get_target_property(dep_path dep BUILD_PATH) to get_target_property(dep_path ${dep} BUILD_PATH) to correctly reference the loop's dependency target. Added a check to skip invalid paths.
2. Replaced xargs with a bash loop: This eliminates xargs' sh fallback entirely. All source commands run in the same bash shell, ensuring your ROS setup scripts (which use bash-specific syntax) work as expected.
3. Single bash context: The entire command runs in one bash process, so environment variables from the setup scripts are preserved when executing ament build.

Alternative: Force xargs to Use Bash #

If you prefer to keep using xargs for some reason, you can explicitly tell it to use bash for each source call:

COMMAND bash -c "echo ${ament_deps} | xargs -r -I {} bash -c 'source {}' ; ament build --symlink-install ${DIR}"

But the bash loop approach is cleaner, more readable, and less prone to edge cases (like path names with spaces, though rare in ROS workspaces).

内容的提问来源于stack exchange，提问作者kutschkem