[RFC,v2,0/7] C++20 migration
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Message ID 20260323102724.1385487-1-barnabas.pocze@ideasonboard.com
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  • C++20 migration
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Barnabás Pőcze March 23, 2026, 10:27 a.m. UTC
With gcc 16 switching C++20 by default, and it being released for more
than five years now, this is a proof of concept patch set containing the
changes needed to make the current CI jobs succeed with cpp_std=c++20.

There is still at least one issue that seemingly only appears in C++20:
https://gitlab.freedesktop.org/camera/libcamera/-/issues/267
the cause is not known, but a potential workaround has been merged.

The last two patches drop the use of `libcamera::Span` in favor of
`std::span`. However, gcc 9 does not have an implementation, so those
two cannot be merged as is.

Barnabás Pőcze (7):
  gstreamer: Add `-Wno-volatile` for GCC
  meson: Ignore `Wredundant-move` with GCC 11 and above
  libcamera: base: log: Ignore deprecations
  treewide: Use character literal instead of string in some cases
  meson: Switch to C++20
  treewide: Use `std::span`
  libcamera: base: span: Deprecate it

 Documentation/guides/pipeline-handler.rst     |  4 +-
 include/libcamera/base/file.h                 | 10 ++--
 include/libcamera/base/span.h                 | 16 +++----
 include/libcamera/base/thread.h               |  4 +-
 include/libcamera/camera.h                    |  5 +-
 include/libcamera/controls.h                  | 22 ++++++---
 include/libcamera/framebuffer.h               | 10 ++--
 .../libcamera/internal/byte_stream_buffer.h   |  6 +--
 include/libcamera/internal/camera_sensor.h    |  6 +--
 .../converter/converter_dw100_vertexmap.h     |  5 +-
 include/libcamera/internal/egl.h              |  8 ++--
 include/libcamera/internal/framebuffer.h      |  4 +-
 .../libcamera/internal/mapped_framebuffer.h   |  4 +-
 include/libcamera/internal/matrix.h           | 26 +++++-----
 include/libcamera/internal/pipeline_handler.h |  2 +-
 include/libcamera/internal/process.h          |  6 +--
 include/libcamera/internal/pub_key.h          |  7 ++-
 .../libcamera/internal/shared_mem_object.h    |  6 +--
 include/libcamera/internal/v4l2_device.h      |  6 +--
 include/libcamera/internal/vector.h           |  4 +-
 meson.build                                   | 23 ++++-----
 src/android/camera_buffer.h                   | 11 +++--
 src/android/camera_capabilities.cpp           |  4 +-
 src/android/camera_request.cpp                |  4 +-
 src/android/jpeg/encoder.h                    |  4 +-
 src/android/jpeg/encoder_jea.cpp              |  2 +-
 src/android/jpeg/encoder_jea.h                |  2 +-
 src/android/jpeg/encoder_libjpeg.cpp          | 10 ++--
 src/android/jpeg/encoder_libjpeg.h            | 12 ++---
 src/android/jpeg/exif.cpp                     |  2 +-
 src/android/jpeg/exif.h                       |  7 ++-
 src/android/jpeg/post_processor_jpeg.cpp      |  2 +-
 src/android/mm/cros_camera_buffer.cpp         |  4 +-
 .../mm/cros_frame_buffer_allocator.cpp        |  2 +-
 src/android/mm/generic_camera_buffer.cpp      |  4 +-
 .../mm/generic_frame_buffer_allocator.cpp     |  2 +-
 src/apps/cam/capture_script.cpp               | 12 ++---
 src/apps/cam/drm.cpp                          |  6 +--
 src/apps/cam/drm.h                            |  4 +-
 src/apps/cam/file_sink.cpp                    |  2 +-
 src/apps/cam/sdl_sink.cpp                     |  4 +-
 src/apps/cam/sdl_texture.h                    |  4 +-
 src/apps/cam/sdl_texture_1plane.cpp           |  2 +-
 src/apps/cam/sdl_texture_1plane.h             |  2 +-
 src/apps/cam/sdl_texture_mjpg.cpp             |  4 +-
 src/apps/cam/sdl_texture_mjpg.h               |  4 +-
 src/apps/cam/sdl_texture_yuv.cpp              |  2 +-
 src/apps/cam/sdl_texture_yuv.h                |  2 +-
 src/apps/common/dng_writer.cpp                |  4 +-
 src/apps/common/image.cpp                     |  6 +--
 src/apps/common/image.h                       | 10 ++--
 src/apps/common/ppm_writer.cpp                |  2 +-
 src/apps/common/ppm_writer.h                  |  4 +-
 src/apps/ipa-verify/main.cpp                  |  4 +-
 src/apps/lc-compliance/helpers/capture.cpp    |  2 +-
 src/apps/lc-compliance/helpers/capture.h      |  2 +-
 src/gstreamer/gstlibcamera-controls.cpp.in    |  4 +-
 src/gstreamer/gstlibcamera-utils.cpp          | 20 ++++----
 src/gstreamer/meson.build                     |  7 +++
 src/ipa/ipu3/algorithms/af.cpp                |  8 ++--
 src/ipa/ipu3/algorithms/af.h                  |  2 +-
 src/ipa/ipu3/algorithms/agc.cpp               |  2 +-
 src/ipa/ipu3/ipu3.cpp                         |  8 ++--
 src/ipa/libipa/exposure_mode_helper.cpp       |  2 +-
 src/ipa/libipa/exposure_mode_helper.h         |  4 +-
 src/ipa/libipa/histogram.cpp                  |  4 +-
 src/ipa/libipa/histogram.h                    |  8 ++--
 src/ipa/libipa/lsc_polynomial.h               |  2 +-
 src/ipa/libipa/v4l2_params.cpp                |  2 +-
 src/ipa/libipa/v4l2_params.h                  | 20 ++++----
 src/ipa/mali-c55/algorithms/agc.cpp           | 10 ++--
 src/ipa/mali-c55/mali-c55.cpp                 |  4 +-
 src/ipa/mali-c55/params.h                     |  2 +-
 src/ipa/rkisp1/algorithms/agc.cpp             |  2 +-
 src/ipa/rkisp1/algorithms/agc.h               |  7 +--
 src/ipa/rkisp1/algorithms/awb.cpp             |  2 +-
 src/ipa/rkisp1/algorithms/lsc.cpp             | 24 +++++-----
 src/ipa/rkisp1/algorithms/lsc.h               |  4 +-
 src/ipa/rkisp1/params.cpp                     |  2 +-
 src/ipa/rkisp1/params.h                       |  8 ++--
 src/ipa/rkisp1/rkisp1.cpp                     |  2 +-
 src/ipa/rpi/cam_helper/cam_helper.cpp         |  4 +-
 src/ipa/rpi/cam_helper/cam_helper.h           |  6 +--
 src/ipa/rpi/cam_helper/cam_helper_imx477.cpp  |  4 +-
 src/ipa/rpi/cam_helper/cam_helper_imx519.cpp  |  4 +-
 src/ipa/rpi/cam_helper/cam_helper_imx708.cpp  |  4 +-
 src/ipa/rpi/cam_helper/md_parser.h            |  9 ++--
 src/ipa/rpi/cam_helper/md_parser_smia.cpp     |  4 +-
 src/ipa/rpi/common/ipa_base.cpp               | 20 ++++----
 src/ipa/rpi/common/ipa_base.h                 |  2 +-
 src/ipa/rpi/controller/af_algorithm.h         |  5 +-
 src/ipa/rpi/controller/rpi/af.cpp             |  2 +-
 src/ipa/rpi/controller/rpi/af.h               |  2 +-
 src/ipa/rpi/controller/rpi/alsc.cpp           |  2 +-
 src/ipa/rpi/pisp/pisp.cpp                     | 12 +++--
 src/ipa/rpi/vc4/vc4.cpp                       | 48 ++++++++++---------
 src/libcamera/base/backtrace.cpp              |  8 ++--
 src/libcamera/base/file.cpp                   |  6 +--
 src/libcamera/base/log.cpp                    | 17 ++++---
 src/libcamera/base/thread.cpp                 |  2 +-
 src/libcamera/byte_stream_buffer.cpp          |  4 +-
 src/libcamera/camera.cpp                      |  2 +-
 src/libcamera/control_serializer.cpp          |  2 +-
 src/libcamera/controls.cpp                    | 22 ++++-----
 src/libcamera/converter/converter_dw100.cpp   |  2 +-
 .../converter/converter_dw100_vertexmap.cpp   |  4 +-
 src/libcamera/egl.cpp                         |  6 +--
 src/libcamera/framebuffer.cpp                 |  6 +--
 src/libcamera/ipa_manager.cpp                 |  2 +-
 src/libcamera/ipa_module.cpp                  | 16 +++----
 src/libcamera/mapped_framebuffer.cpp          |  2 +-
 src/libcamera/matrix.cpp                      | 26 +++++-----
 src/libcamera/media_pipeline.cpp              |  6 +--
 src/libcamera/pipeline/imx8-isi/imx8-isi.cpp  |  4 +-
 src/libcamera/pipeline/ipu3/ipu3.cpp          |  6 +--
 src/libcamera/pipeline/mali-c55/mali-c55.cpp  |  6 +--
 src/libcamera/pipeline/rkisp1/rkisp1.cpp      |  6 +--
 src/libcamera/pipeline/rkisp1/rkisp1_path.cpp |  2 +-
 src/libcamera/pipeline/rkisp1/rkisp1_path.h   |  6 +--
 .../pipeline/rpi/common/pipeline_base.cpp     | 12 ++---
 .../pipeline/rpi/common/pipeline_base.h       |  2 +-
 src/libcamera/pipeline/rpi/pisp/pisp.cpp      |  4 +-
 src/libcamera/pipeline/rpi/vc4/vc4.cpp        |  2 +-
 src/libcamera/pipeline/simple/simple.cpp      | 10 ++--
 src/libcamera/pipeline/uvcvideo/uvcvideo.cpp  |  6 +--
 src/libcamera/pipeline/vimc/vimc.cpp          |  6 +--
 src/libcamera/pipeline/virtual/virtual.cpp    |  6 +--
 src/libcamera/process.cpp                     |  4 +-
 src/libcamera/pub_key.cpp                     |  6 +--
 src/libcamera/sensor/camera_sensor_legacy.cpp |  8 ++--
 src/libcamera/sensor/camera_sensor_raw.cpp    |  8 ++--
 src/libcamera/shared_mem_object.cpp           |  2 +-
 src/libcamera/v4l2_device.cpp                 | 14 +++---
 src/libcamera/v4l2_videodevice.cpp            |  6 +--
 src/libcamera/vector.cpp                      |  2 +-
 src/libcamera/yaml_parser.cpp                 |  2 +-
 src/py/libcamera/py_helpers.cpp               |  2 +-
 src/py/libcamera/py_main.cpp                  |  4 +-
 src/v4l2/v4l2_camera_proxy.cpp                |  2 +-
 src/v4l2/v4l2_compat_manager.cpp              |  4 +-
 test/controls/control_value.cpp               | 28 +++++------
 test/file.cpp                                 |  2 +-
 test/span.cpp                                 |  1 +
 test/utils.cpp                                |  4 +-
 test/v4l2_videodevice/controls.cpp            |  4 +-
 utils/codegen/controls.py                     |  4 +-
 utils/gen-debug-controls.py                   |  4 +-
 147 files changed, 487 insertions(+), 461 deletions(-)

--
2.53.0

Comments

Kieran Bingham March 23, 2026, 5:10 p.m. UTC | #1
Quoting Barnabás Pőcze (2026-03-23 10:27:17)
> With gcc 16 switching C++20 by default, and it being released for more
> than five years now, this is a proof of concept patch set containing the
> changes needed to make the current CI jobs succeed with cpp_std=c++20.
> 
> There is still at least one issue that seemingly only appears in C++20:
> https://gitlab.freedesktop.org/camera/libcamera/-/issues/267
> the cause is not known, but a potential workaround has been merged.
> 
> The last two patches drop the use of `libcamera::Span` in favor of
> `std::span`. However, gcc 9 does not have an implementation, so those
> two cannot be merged as is.

Perhaps we should consider merging the first 5 patches already then to
support with the migration?

Can we in anyway 'alias' std::span to libcamera::Span for gcc-9, so we
could already move forwards ? or would that get too messy ?

> 
> Barnabás Pőcze (7):
>   gstreamer: Add `-Wno-volatile` for GCC
>   meson: Ignore `Wredundant-move` with GCC 11 and above
>   libcamera: base: log: Ignore deprecations
>   treewide: Use character literal instead of string in some cases
>   meson: Switch to C++20
>   treewide: Use `std::span`
>   libcamera: base: span: Deprecate it
> 
>  Documentation/guides/pipeline-handler.rst     |  4 +-
>  include/libcamera/base/file.h                 | 10 ++--
>  include/libcamera/base/span.h                 | 16 +++----
>  include/libcamera/base/thread.h               |  4 +-
>  include/libcamera/camera.h                    |  5 +-
>  include/libcamera/controls.h                  | 22 ++++++---
>  include/libcamera/framebuffer.h               | 10 ++--
>  .../libcamera/internal/byte_stream_buffer.h   |  6 +--
>  include/libcamera/internal/camera_sensor.h    |  6 +--
>  .../converter/converter_dw100_vertexmap.h     |  5 +-
>  include/libcamera/internal/egl.h              |  8 ++--
>  include/libcamera/internal/framebuffer.h      |  4 +-
>  .../libcamera/internal/mapped_framebuffer.h   |  4 +-
>  include/libcamera/internal/matrix.h           | 26 +++++-----
>  include/libcamera/internal/pipeline_handler.h |  2 +-
>  include/libcamera/internal/process.h          |  6 +--
>  include/libcamera/internal/pub_key.h          |  7 ++-
>  .../libcamera/internal/shared_mem_object.h    |  6 +--
>  include/libcamera/internal/v4l2_device.h      |  6 +--
>  include/libcamera/internal/vector.h           |  4 +-
>  meson.build                                   | 23 ++++-----
>  src/android/camera_buffer.h                   | 11 +++--
>  src/android/camera_capabilities.cpp           |  4 +-
>  src/android/camera_request.cpp                |  4 +-
>  src/android/jpeg/encoder.h                    |  4 +-
>  src/android/jpeg/encoder_jea.cpp              |  2 +-
>  src/android/jpeg/encoder_jea.h                |  2 +-
>  src/android/jpeg/encoder_libjpeg.cpp          | 10 ++--
>  src/android/jpeg/encoder_libjpeg.h            | 12 ++---
>  src/android/jpeg/exif.cpp                     |  2 +-
>  src/android/jpeg/exif.h                       |  7 ++-
>  src/android/jpeg/post_processor_jpeg.cpp      |  2 +-
>  src/android/mm/cros_camera_buffer.cpp         |  4 +-
>  .../mm/cros_frame_buffer_allocator.cpp        |  2 +-
>  src/android/mm/generic_camera_buffer.cpp      |  4 +-
>  .../mm/generic_frame_buffer_allocator.cpp     |  2 +-
>  src/apps/cam/capture_script.cpp               | 12 ++---
>  src/apps/cam/drm.cpp                          |  6 +--
>  src/apps/cam/drm.h                            |  4 +-
>  src/apps/cam/file_sink.cpp                    |  2 +-
>  src/apps/cam/sdl_sink.cpp                     |  4 +-
>  src/apps/cam/sdl_texture.h                    |  4 +-
>  src/apps/cam/sdl_texture_1plane.cpp           |  2 +-
>  src/apps/cam/sdl_texture_1plane.h             |  2 +-
>  src/apps/cam/sdl_texture_mjpg.cpp             |  4 +-
>  src/apps/cam/sdl_texture_mjpg.h               |  4 +-
>  src/apps/cam/sdl_texture_yuv.cpp              |  2 +-
>  src/apps/cam/sdl_texture_yuv.h                |  2 +-
>  src/apps/common/dng_writer.cpp                |  4 +-
>  src/apps/common/image.cpp                     |  6 +--
>  src/apps/common/image.h                       | 10 ++--
>  src/apps/common/ppm_writer.cpp                |  2 +-
>  src/apps/common/ppm_writer.h                  |  4 +-
>  src/apps/ipa-verify/main.cpp                  |  4 +-
>  src/apps/lc-compliance/helpers/capture.cpp    |  2 +-
>  src/apps/lc-compliance/helpers/capture.h      |  2 +-
>  src/gstreamer/gstlibcamera-controls.cpp.in    |  4 +-
>  src/gstreamer/gstlibcamera-utils.cpp          | 20 ++++----
>  src/gstreamer/meson.build                     |  7 +++
>  src/ipa/ipu3/algorithms/af.cpp                |  8 ++--
>  src/ipa/ipu3/algorithms/af.h                  |  2 +-
>  src/ipa/ipu3/algorithms/agc.cpp               |  2 +-
>  src/ipa/ipu3/ipu3.cpp                         |  8 ++--
>  src/ipa/libipa/exposure_mode_helper.cpp       |  2 +-
>  src/ipa/libipa/exposure_mode_helper.h         |  4 +-
>  src/ipa/libipa/histogram.cpp                  |  4 +-
>  src/ipa/libipa/histogram.h                    |  8 ++--
>  src/ipa/libipa/lsc_polynomial.h               |  2 +-
>  src/ipa/libipa/v4l2_params.cpp                |  2 +-
>  src/ipa/libipa/v4l2_params.h                  | 20 ++++----
>  src/ipa/mali-c55/algorithms/agc.cpp           | 10 ++--
>  src/ipa/mali-c55/mali-c55.cpp                 |  4 +-
>  src/ipa/mali-c55/params.h                     |  2 +-
>  src/ipa/rkisp1/algorithms/agc.cpp             |  2 +-
>  src/ipa/rkisp1/algorithms/agc.h               |  7 +--
>  src/ipa/rkisp1/algorithms/awb.cpp             |  2 +-
>  src/ipa/rkisp1/algorithms/lsc.cpp             | 24 +++++-----
>  src/ipa/rkisp1/algorithms/lsc.h               |  4 +-
>  src/ipa/rkisp1/params.cpp                     |  2 +-
>  src/ipa/rkisp1/params.h                       |  8 ++--
>  src/ipa/rkisp1/rkisp1.cpp                     |  2 +-
>  src/ipa/rpi/cam_helper/cam_helper.cpp         |  4 +-
>  src/ipa/rpi/cam_helper/cam_helper.h           |  6 +--
>  src/ipa/rpi/cam_helper/cam_helper_imx477.cpp  |  4 +-
>  src/ipa/rpi/cam_helper/cam_helper_imx519.cpp  |  4 +-
>  src/ipa/rpi/cam_helper/cam_helper_imx708.cpp  |  4 +-
>  src/ipa/rpi/cam_helper/md_parser.h            |  9 ++--
>  src/ipa/rpi/cam_helper/md_parser_smia.cpp     |  4 +-
>  src/ipa/rpi/common/ipa_base.cpp               | 20 ++++----
>  src/ipa/rpi/common/ipa_base.h                 |  2 +-
>  src/ipa/rpi/controller/af_algorithm.h         |  5 +-
>  src/ipa/rpi/controller/rpi/af.cpp             |  2 +-
>  src/ipa/rpi/controller/rpi/af.h               |  2 +-
>  src/ipa/rpi/controller/rpi/alsc.cpp           |  2 +-
>  src/ipa/rpi/pisp/pisp.cpp                     | 12 +++--
>  src/ipa/rpi/vc4/vc4.cpp                       | 48 ++++++++++---------
>  src/libcamera/base/backtrace.cpp              |  8 ++--
>  src/libcamera/base/file.cpp                   |  6 +--
>  src/libcamera/base/log.cpp                    | 17 ++++---
>  src/libcamera/base/thread.cpp                 |  2 +-
>  src/libcamera/byte_stream_buffer.cpp          |  4 +-
>  src/libcamera/camera.cpp                      |  2 +-
>  src/libcamera/control_serializer.cpp          |  2 +-
>  src/libcamera/controls.cpp                    | 22 ++++-----
>  src/libcamera/converter/converter_dw100.cpp   |  2 +-
>  .../converter/converter_dw100_vertexmap.cpp   |  4 +-
>  src/libcamera/egl.cpp                         |  6 +--
>  src/libcamera/framebuffer.cpp                 |  6 +--
>  src/libcamera/ipa_manager.cpp                 |  2 +-
>  src/libcamera/ipa_module.cpp                  | 16 +++----
>  src/libcamera/mapped_framebuffer.cpp          |  2 +-
>  src/libcamera/matrix.cpp                      | 26 +++++-----
>  src/libcamera/media_pipeline.cpp              |  6 +--
>  src/libcamera/pipeline/imx8-isi/imx8-isi.cpp  |  4 +-
>  src/libcamera/pipeline/ipu3/ipu3.cpp          |  6 +--
>  src/libcamera/pipeline/mali-c55/mali-c55.cpp  |  6 +--
>  src/libcamera/pipeline/rkisp1/rkisp1.cpp      |  6 +--
>  src/libcamera/pipeline/rkisp1/rkisp1_path.cpp |  2 +-
>  src/libcamera/pipeline/rkisp1/rkisp1_path.h   |  6 +--
>  .../pipeline/rpi/common/pipeline_base.cpp     | 12 ++---
>  .../pipeline/rpi/common/pipeline_base.h       |  2 +-
>  src/libcamera/pipeline/rpi/pisp/pisp.cpp      |  4 +-
>  src/libcamera/pipeline/rpi/vc4/vc4.cpp        |  2 +-
>  src/libcamera/pipeline/simple/simple.cpp      | 10 ++--
>  src/libcamera/pipeline/uvcvideo/uvcvideo.cpp  |  6 +--
>  src/libcamera/pipeline/vimc/vimc.cpp          |  6 +--
>  src/libcamera/pipeline/virtual/virtual.cpp    |  6 +--
>  src/libcamera/process.cpp                     |  4 +-
>  src/libcamera/pub_key.cpp                     |  6 +--
>  src/libcamera/sensor/camera_sensor_legacy.cpp |  8 ++--
>  src/libcamera/sensor/camera_sensor_raw.cpp    |  8 ++--
>  src/libcamera/shared_mem_object.cpp           |  2 +-
>  src/libcamera/v4l2_device.cpp                 | 14 +++---
>  src/libcamera/v4l2_videodevice.cpp            |  6 +--
>  src/libcamera/vector.cpp                      |  2 +-
>  src/libcamera/yaml_parser.cpp                 |  2 +-
>  src/py/libcamera/py_helpers.cpp               |  2 +-
>  src/py/libcamera/py_main.cpp                  |  4 +-
>  src/v4l2/v4l2_camera_proxy.cpp                |  2 +-
>  src/v4l2/v4l2_compat_manager.cpp              |  4 +-
>  test/controls/control_value.cpp               | 28 +++++------
>  test/file.cpp                                 |  2 +-
>  test/span.cpp                                 |  1 +
>  test/utils.cpp                                |  4 +-
>  test/v4l2_videodevice/controls.cpp            |  4 +-
>  utils/codegen/controls.py                     |  4 +-
>  utils/gen-debug-controls.py                   |  4 +-
>  147 files changed, 487 insertions(+), 461 deletions(-)
> 
> --
> 2.53.0