Enable compliance with -Wshadow by renaming variables.

[leander-dsouza]

Basic Info

Info	Please fill out this column
Ticket(s) this addresses	N/A
Primary OS tested on	Ubuntu
Is this a breaking change?	No

---

Description of the problem

• When including the <cv_bridge/cv_bridge.hpp> header, explicit ignores for shadowing had to be passed in order to build with -Wshadow:

  #pragma GCC diagnostic push
  #pragma GCC diagnostic ignored "-Wshadow"
  #include <cv_bridge/cv_bridge.hpp>
  #pragma GCC diagnostic pop

• This can be explicitly checked by building the package on its own:

  $ colcon build --packages-select cv_bridge --cmake-args -DCMAKE_CXX_FLAGS="-Wshadow -Werror=shadow"
  Starting >>> cv_bridge
  --- stderr: cv_bridge                             
  In file included from /autonomy_ws/src/vision_opencv/cv_bridge/src/cv_bridge.cpp:37:
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp: In constructor ‘cv_bridge::CvImage::CvImage(const std_msgs::msg::Header&, const std::string&, const cv::Mat&)’:
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp:102:21: error: declaration of ‘image’ shadows a member of ‘cv_bridge::CvImage’ [-Werror=shadow]
    102 |     const cv::Mat & image = cv::Mat())
        |     ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp:90:11: note: shadowed declaration is here
     90 |   cv::Mat image;           // !< Image data for use with OpenCV
        |           ^~~~~
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp:101:63: error: declaration of ‘encoding’ shadows a member of ‘cv_bridge::CvImage’ [-Werror=shadow]
    101 |     const std_msgs::msg::Header & header, const std::string & encoding,
        |                                           ~~~~~~~~~~~~~~~~~~~~^~~~~~~~
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp:89:15: note: shadowed declaration is here
     89 |   std::string encoding;    // !< Image encoding ("mono8", "bgr8", etc.)
        |               ^~~~~~~~
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp:101:35: error: declaration of ‘header’ shadows a member of ‘cv_bridge::CvImage’ [-Werror=shadow]
    101 |     const std_msgs::msg::Header & header, const std::string & encoding,
        |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp:88:25: note: shadowed declaration is here
     88 |   std_msgs::msg::Header header;  // !< ROS header
        |                         ^~~~~~
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp: In constructor ‘cv_bridge::CvImage::CvImage(const std_msgs::msg::Header&, const std::string&, const cv::Mat&)’:
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp:102:21: error: declaration of ‘image’ shadows a member of ‘cv_bridge::CvImage’ [-Werror=shadow]
    102 |     const cv::Mat & image = cv::Mat())
        |     ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp:90:11: note: shadowed declaration is here
     90 |   cv::Mat image;           // !< Image data for use with OpenCV
        |           ^~~~~
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp:101:63: error: declaration of ‘encoding’ shadows a member of ‘cv_bridge::CvImage’ [-Werror=shadow]
    101 |     const std_msgs::msg::Header & header, const std::string & encoding,
        |                                           ~~~~~~~~~~~~~~~~~~~~^~~~~~~~
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp:89:15: note: shadowed declaration is here
     89 |   std::string encoding;    // !< Image encoding ("mono8", "bgr8", etc.)
        |               ^~~~~~~~
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp:101:35: error: declaration of ‘header’ shadows a member of ‘cv_bridge::CvImage’ [-Werror=shadow]
    101 |     const std_msgs::msg::Header & header, const std::string & encoding,
        |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp:88:25: note: shadowed declaration is here
     88 |   std_msgs::msg::Header header;  // !< ROS header
        |                         ^~~~~~
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp: In constructor ‘cv_bridge::CvImage::CvImage(const std_msgs::msg::Header&, const std::string&, const cv::Mat&)’:
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp:102:21: error: declaration of ‘image’ shadows a member of ‘cv_bridge::CvImage’ [-Werror=shadow]
    102 |     const cv::Mat & image = cv::Mat())
        |     ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp:90:11: note: shadowed declaration is here
     90 |   cv::Mat image;           // !< Image data for use with OpenCV
        |           ^~~~~
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp:101:63: error: declaration of ‘encoding’ shadows a member of ‘cv_bridge::CvImage’ [-Werror=shadow]
    101 |     const std_msgs::msg::Header & header, const std::string & encoding,
        |                                           ~~~~~~~~~~~~~~~~~~~~^~~~~~~~
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp:89:15: note: shadowed declaration is here
     89 |   std::string encoding;    // !< Image encoding ("mono8", "bgr8", etc.)
        |               ^~~~~~~~
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp:101:35: error: declaration of ‘header’ shadows a member of ‘cv_bridge::CvImage’ [-Werror=shadow]
    101 |     const std_msgs::msg::Header & header, const std::string & encoding,
        |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp:88:25: note: shadowed declaration is here
     88 |   std_msgs::msg::Header header;  // !< ROS header
        |                         ^~~~~~
  /autonomy_ws/src/vision_opencv/cv_bridge/src/cv_bridge.cpp: In member function ‘void cv_bridge::CvImage::toCompressedImageMsg(sensor_msgs::msg::CompressedImage&, cv_bridge::Format) const’:
  /autonomy_ws/src/vision_opencv/cv_bridge/src/cv_bridge.cpp:517:11: error: declaration of ‘image’ shadows a member of ‘cv_bridge::CvImage’ [-Werror=shadow]
    517 |   cv::Mat image;
        |           ^~~~~
  /autonomy_ws/src/vision_opencv/cv_bridge/src/../include/cv_bridge/cv_bridge.hpp:90:11: note: shadowed declaration is here
     90 |   cv::Mat image;           // !< Image data for use with OpenCV
        |           ^~~~~
  cc1plus: some warnings being treated as errors
  gmake[2]: *** [src/CMakeFiles/cv_bridge.dir/build.make:76: src/CMakeFiles/cv_bridge.dir/cv_bridge.cpp.o] Error 1
  gmake[1]: *** [CMakeFiles/Makefile2:245: src/CMakeFiles/cv_bridge.dir/all] Error 2
  gmake: *** [Makefile:146: all] Error 2
  ---
  Failed   <<< cv_bridge [2.21s, exited with code 2]

Resolution and Testing

• After renaming some of the variables to be devoid of shadowing faults, the build and test now pass cleanly:

  colcon build --packages-select cv_bridge --cmake-args -DCMAKE_CXX_FLAGS="-Wshadow -Werror=shadow" && colcon test --packages-select cv_bridge