supporting protobuf v22 and later(with abseil-cpp/C++17) by Kumataro · Pull Request #24372 · opencv/opencv

Kumataro · 2023-10-08T00:52:02Z

fix #24369
related #23791

This patch supports external protobuf v22 and later, it required abseil-cpp and c++17.
Even if the built-in protobuf is upgraded to v22 or later,
the dependency on abseil-cpp and the requirement for C++17 will continue.
Some test for caffe required patched protobuf, so this patch disable them.

This patch is tested by following libraries.

Protobuf: /usr/local/lib/libprotobuf.so (4.24.4)
abseil-cpp: YES (20230125)

Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

I agree to contribute to the project under Apache 2 License.
To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
The PR is proposed to the proper branch
There is a reference to the original bug report and related work
There is accuracy test, performance test and test data in opencv_extra repository, if applicable
Patch to opencv_extra has the same branch name.
The feature is well documented and sample code can be built with the project CMake

Kumataro · 2023-10-09T09:58:25Z

I was relieved that the test passed completely.

And this patch requires special setting to install protobuf v24+.

How to install external protobuf v24 and abseil-cpp at Ubuntu 23.04.

git clone https://github.com/protocolbuffers/protobuf.git
cd protobuf
  git checkout v4.24.4
  git reset --hard
  git submodule update --init --recursive
cd ..

cmake -S protobuf/third_party/abseil-cpp/ -B build_absl -GNinja -DCMAKE_CXX_STANDARD=17
cmake --build build_absl
sudo cmake --install build_absl
sudo ldconfig

cmake -S protobuf/ -B build_protobuf -GNinja -Dprotobuf_BUILD_TESTS=OFF -Dprotobuf_BUILD_SHARED_LIBS=ON -DCMAKE_CXX_STANDARD=17
cmake --build build_protobuf
sudo cmake --install build_protobuf
sudo ldconfig

After that, we can detect protobuf and absl-* at pkg-config --list-all.

To test building opencv4 with options.

cmake -S opencv -B build4-main_cxx17 -DCMAKE_CXX_STANDARD=17 -GNinja -DBUILD_PROTOBUF=OFF -DPROTOBUF_UPDATE_FILES=ON
cmake --build main_cxx17

If no patch, there are following errors.

/usr/bin/ld: modules/dnn/CMakeFiles/opencv_dnn.dir/attr_value.pb.cc.o: in function `absl::lts_20230125::log_internal::LogMessage& absl::lts_20230125::log_internal::LogMessage::operator<< <34>(char const (&) [34])':
attr_value.pb.cc:(.text._ZN4absl12lts_2023012512log_internal10LogMessagelsILi34EEERS2_RAT__Kc[_ZN4absl12lts_2023012512log_internal10LogMessagelsILi34EEERS2_RAT__Kc]+0x24): undefined reference to `absl::lts_20230125::log_internal::LogMessage::CopyToEncodedBuffer(std::basic_string_view<char, std::char_traits<char> >, absl::lts_20230125::log_internal::LogMessage::StringType)'
/usr/bin/ld: modules/dnn/CMakeFiles/opencv_dnn.dir/attr_value.pb.cc.o: in function `google::protobuf::MapKey::type() const [clone .part.0]':
...

modules/dnn/test/test_layers.cpp

modules/dnn/src/caffe/caffe_io.cpp

dkurt · 2023-10-09T10:24:07Z

cmake/OpenCVFindProtobuf.cmake

+
+if(HAVE_ABSL_STRINGS AND HAVE_ABSL_LOG)
+  list(APPEND CUSTOM_STATUS absl)
+  list(APPEND CUSTOM_STATUS_absl "      abseil-cpp:" "YES (${ABSL_STRINGS_VERSION})" )


abseil-cpp is a direct dependency of Protobuf, not OpenCV. Not sure that it has to be reported.

When using protobuf v22 or later,
the dnn module directly references abseil-cpp library ( via *.pb.cc converted *.pb with protoc ).

Unfortunally, there is also a possibility that OpenCV Users may use a combination of protobuf and abseil-cpp versions that are not expected.

I think it is better to leave abseil-cpp version information as a cmake log.
It is helpful to investifate compile/runtime errors

kmtr@kmtr-VMware-Virtual-Platform:~/work/build4-main_cxx17/modules/dnn/CMakeFiles/opencv_dnn.dir$ nm attr_value.pb.cc.o | c++filt | grep "absl" | head -10 U absl::lts_20230125::log_internal::LogMessage::OstreamView::stream() U absl::lts_20230125::log_internal::LogMessage::OstreamView::OstreamView(absl::lts_20230125::log_internal::LogMessage::LogMessageData&) U absl::lts_20230125::log_internal::LogMessage::OstreamView::~OstreamView() U absl::lts_20230125::log_internal::LogMessage::CopyToEncodedBuffer(std::basic_string_view<char, std::char_traits<char> >, absl::lts_20230125::log_internal::LogMessage::StringType) 0000000000000000 W absl::lts_20230125::log_internal::LogMessage& absl::lts_20230125::log_internal::LogMessage::operator<< <14>(char const (&) [14]) 0000000000000000 W absl::lts_20230125::log_internal::LogMessage& absl::lts_20230125::log_internal::LogMessage::operator<< <22>(char const (&) [22]) 0000000000000000 W absl::lts_20230125::log_internal::LogMessage& absl::lts_20230125::log_internal::LogMessage::operator<< <23>(char const (&) [23]) 0000000000000000 W absl::lts_20230125::log_internal::LogMessage& absl::lts_20230125::log_internal::LogMessage::operator<< <2>(char const (&) [2]) 0000000000000000 W absl::lts_20230125::log_internal::LogMessage& absl::lts_20230125::log_internal::LogMessage::operator<< <34>(char const (&) [34]) 0000000000000000 t absl::lts_20230125::log_internal::LogMessage& absl::lts_20230125::log_internal::LogMessage::operator<< <48>(char const (&) [48]) [clone .isra.0]

I thought about it additionally.

When a user builds a protobuf, it is fully expected that the appropriate abseil-cpp version will be applied in the git submodule.

Therefore, I would like to delete the version log. thank you very much!

e.g. https://github.com/protocolbuffers/protobuf/tree/main/third_party

abseil-cpp @ fb3621f Update to latest absl LTS patch 20230802.1 (#14145)

I removed it, thank you for your comment !

modules/dnn/CMakeLists.txt

shr-project · 2023-10-10T13:02:19Z

modules/dnn/CMakeLists.txt

 ocv_add_accuracy_tests(${dnn_runtime_libs})

+if(NOT BUILD_PROTOBUF)
+  ocv_target_compile_definitions(opencv_test_dnn PRIVATE "OPENCV_DNN_EXTERNAL_PROTOBUF=1")


Does this need "if(TARGET opencv_test_dnn)" as well? I'm seeing:

CMake Error at cmake/OpenCVUtils.cmake:1517 (message): ocv_target_compile_definitions: invalid target: 'opencv_test_dnn' Call Stack (most recent call first): modules/dnn/CMakeLists.txt:258 (ocv_target_compile_definitions)

Hello, thank you for your comment, I agree with you.
When ENABLE_TESTS=OFF, same problem is occured.
I push additional patch to fix it.

shr-project · 2023-10-10T14:39:43Z

Thanks, tested in OpenEmbedded environment where I've first seen this issue and with these changes it builds fine again. Thank you!

mshabunin · 2023-10-11T08:56:20Z

cmake/OpenCVFindProtobuf.cmake

+                message(FATAL_ERROR "protobuf(v22 and later) and abseil-cpp request CMAKE_CXX_STANDARD=17 and later.")
+            endif()
+
+            ocv_check_modules(ABSL_STRINGS absl_strings)


Does abseil has cmake package? Can we use find_package instead of pkg_config and find_library?

mshabunin · 2023-10-11T09:10:56Z

Some time ago I've been able to build OpenCV with latest protobuf: #23791 (comment) And I did not need to explicitly link with abseil. Did something change over time or was my configuration different than yours in some way? Maybe you don't need to build abseil separately then it will be built as part of protobuf and will be linked automatically?

Kumataro · 2023-10-11T09:56:50Z

Maybe you don't need to build abseil separately then it will be built as part of protobuf and will be linked automatically?

Thank you for your comment.

I found https://protobuf.dev/support/migration/#abseil

There are two ways protobuf references abseil-cpp.

protobuf_ABSL_PROVIDER=module (abseil-cpp will be included in protobuf)
protobuf_ABSL_PROVIDER=package (protobuf refers external abseil-cpp)

If abseil-cpp is installed manually in the system before running cmake for protobuf, option 2, that is using external abseil-cpp package, is selected.

Sorry, I'll need some time to work.
My current idea is ....

Search for abseil-cpp with find_package().
If found, add abseil string and abseil log to the link targets of the dnn module with protobuf
(If not ) Only protobuf will be linked for the dnn module.

---- Add comment
Maybe it is not good idea. I can build protobuf including absl-cpp, but if I try to install protobuf, absl-cpp seems to be installed already...

kmtr@kmtr-VMware-Virtual-Platform:~/work/build_protobuf$ sudo ninja install | egrep "protobuf.pc|absl_strings.pc"
-- Up-to-date: /usr/local/lib/pkgconfig/absl_strings.pc
-- Up-to-date: /usr/local/lib/pkgconfig/protobuf.pc

kmtr@kmtr-VMware-Virtual-Platform:~/work/build_protobuf$ nm libprotobuf.so | c++filt | grep " t absl" | head -10
000000000034be74 t absl::lts_20230125::CordBuffer::ConsumeValue(std::basic_string_view<char, std::char_traits<char> >&)
000000000034c13e t absl::lts_20230125::CordBuffer::available_up_to(unsigned long)
000000000034c256 t absl::lts_20230125::CordBuffer::IncreaseLengthBy(unsigned long)
000000000034bfae t absl::lts_20230125::CordBuffer::CreateWithDefaultLimit(unsigned long)
000000000034bc00 t absl::lts_20230125::CordBuffer::Rep::long_available()
000000000034bb88 t absl::lts_20230125::CordBuffer::Rep::short_available()
000000000034bd46 t absl::lts_20230125::CordBuffer::Rep::add_short_length(unsigned long)
000000000034bd22 t absl::lts_20230125::CordBuffer::Rep::set_short_length(unsigned long)
000000000034be56 t absl::lts_20230125::CordBuffer::Rep::Long::Long(absl::lts_20230125::cord_internal::CordRepFlat*)
000000000034be56 t absl::lts_20230125::CordBuffer::Rep::Long::Long(absl::lts_20230125::cord_internal::CordRepFlat*)

mshabunin · 2023-10-11T12:52:29Z

I tried to build protobuf@24.x and OpenCV. As in previous result only minor patch was needed (replace Protobuf prefix with protobuf in two places, see link in my previous comment). Apparently when using Protobuf name, cmake's own search method will be used which does not set imported targets property correctly, that is why it is necessary to search for protobuf package.

protobuf cmake package already searches for abseil (see protobuf-config.cmake):

if(NOT TARGET absl::strings)
  find_package(absl CONFIG)
endif()

and imported target already provides required interface link libraries (see protobuf-targets.cmake):

# Create imported target protobuf::libprotobuf
add_library(protobuf::libprotobuf SHARED IMPORTED)

set_target_properties(protobuf::libprotobuf PROPERTIES
  INTERFACE_COMPILE_DEFINITIONS "PROTOBUF_USE_DLLS"
  INTERFACE_COMPILE_FEATURES "cxx_std_14"
  INTERFACE_INCLUDE_DIRECTORIES "${_IMPORT_PREFIX}/include"
  INTERFACE_LINK_LIBRARIES "absl::absl_check;absl::absl_log;absl::algorithm;absl::base;absl::bind_front;absl::bits;absl::btree;absl::cleanup;absl::cord;absl::core_headers;absl::debugging;absl::die_if_null;absl::dynamic_annotations;absl::flags;absl::flat_hash_map;absl::flat_hash_set;absl::function_ref;absl::hash;absl::layout;absl::log_initialize;absl::log_severity;absl::memory;absl::node_hash_map;absl::node_hash_set;absl::optional;absl::span;absl::status;absl::statusor;absl::strings;absl::synchronization;absl::time;absl::type_traits;absl::utility;absl::variant"
)

My script:

PD=/work/protobuf/.build

build_pb() {
    rm -rf ${PD}
    mkdir -p ${PD} && pushd ${PD}
    cmake -GNinja \
        -DCMAKE_BUILD_TYPE=Release \
        -Dprotobuf_BUILD_TESTS=OFF \
        -DCMAKE_POSITION_INDEPENDENT_CODE=ON \ # need to be compatible with dynamic linkage
        -DCMAKE_INSTALL_PREFIX=install \
        -Dprotobuf_BUILD_SHARED_LIBS=ON \ # static works as well
        ..
    ninja install
    popd
}

build_opencv() {
    export LD_LIBRARY_PATH=${PD}/install/lib:${LD_LIBRARY_PATH} # need to set this for protoc to work
    mkdir -p $D
    pushd $D && rm -rf *
    cmake \
        -DCMAKE_BUILD_TYPE=Release \
        -DCMAKE_PREFIX_PATH=${PD}/install \
        -DWITH_PROTOBUF=ON \
        -DBUILD_PROTOBUF=OFF \
        -DPROTOBUF_UPDATE_FILES=ON \
        -Dprotobuf_MODULE_COMPATIBLE=ON \ # we still need this for command PROTOBUF_GENERATE_CPP
        -DCMAKE_CXX_STANDARD=17 \
        -DCMAKE_BUILD_TYPE=Release \
        -DWITH_OPENCL=OFF \
        ../opencv
    ninja
    popd
}

build_pb
build_opencv

In previous PR I promised to integrate this patch to OpenCV, but completely forgot about it 🤦

Kumataro · 2023-10-11T15:47:12Z

I'm sorry to not finished this fix.
It seems that my trial to remove direct-referencing absl-cpp libraries doesn't work well.
I think my operation maybe has some mistakes. I'll re-think about it calmly tomorrow(today).

I tried with Ubuntu23.04.

(1) libs in modules/dnn/CMakefile is "ocv.3rdparty.flatbuffers;protobuf::libprotobuf". It is OK.
(2) when linking dnn module, the referenced external library is only libprotobuf.so, not absl-cpp. So there are some undefined symbols.
(3) pkg-config protobuf --libs outputs with absl libraries.

(1)

-- opencv_dnn: filter out cuda4dnn source code
-- opencv_dnn: ocv_create_module( ocv.3rdparty.flatbuffers protobuf::libprotobuf )
-- Excluding from source files list: <BUILD>/modules/dnn/layers/layers_common.avx.cpp

(2)

 modules/dnn/CMakeFiles/opencv_dnn.dir/opencl_kernels_dnn.cpp.o
 modules/dnn/CMakeFiles/opencv_dnn.dir/layers/cpu_kernels/fast_gemm_kernels.neon.cpp.o
  -Wl,-rpath,/home/kmtr/work/build4-main_cxx17/lib:/usr/local/lib:  
lib/libopencv_imgproc.so.4.8.0  -ldl  -lm  -lpthread  -lrt  
3rdparty/lib/libtegra_hal.a  
/usr/local/lib/libprotobuf.so  
lib/libopencv_core.so.4.8.0 && :

(3)

kmtr@ubuntu:~/work/build4-main_cxx17$ pkg-config protobuf --libs
-L/usr/local/lib -lprotobuf -labsl_log_internal_check_op -labsl_leak_check -labsl_die_if_null -labsl_log_internal_conditions -labsl_log_internal_message -labsl_examine_stack -labsl_log_internal_format -labsl_log_internal_proto -labsl_log_internal_nullguard -labsl_log_internal_log_sink_set -labsl_log_sink -labsl_log_entry -labsl_flags -labsl_flags_internal -labsl_flags_marshalling -labsl_flags_reflection -labsl_flags_private_handle_accessor -labsl_flags_commandlineflag -labsl_flags_commandlineflag_internal -labsl_flags_config -labsl_flags_program_name -labsl_log_initialize -labsl_log_globals -labsl_log_internal_globals -labsl_hash -labsl_city -labsl_low_level_hash -labsl_raw_hash_set -labsl_hashtablez_sampler -labsl_statusor -labsl_status -labsl_cord -labsl_cordz_info -labsl_cord_internal -labsl_cordz_functions -labsl_exponential_biased -labsl_cordz_handle -labsl_crc_cord_state -labsl_crc32c -labsl_crc_internal -labsl_crc_cpu_detect -labsl_bad_optional_access -labsl_str_format_internal -labsl_strerror -labsl_synchronization -labsl_graphcycles_internal -labsl_stacktrace -labsl_symbolize -labsl_debugging_internal -labsl_demangle_internal -labsl_malloc_internal -labsl_time -labsl_civil_time -labsl_time_zone -labsl_bad_variant_access -lutf8_validity -lutf8_range -labsl_strings -labsl_strings_internal -lrt -labsl_base -labsl_spinlock_wait -labsl_int128 -labsl_throw_delegate -labsl_raw_logging_internal -labsl_log_severity

Kumataro · 2023-10-11T21:34:11Z

Hello, I made the workaround clearly. ( I'll fix it after my job.. )

I tried to debug following command to check protobuf-targets.cmake is available.

message("${libs}")
include(CMakePrintHelpers)
CMAKE_PRINT_PROPERTIES(TARGETS "protobuf::libprotobuf" PROPERTIES INTERFACE_COMPILE_DEFINITIONS INTERFACE_COMPILE_FEA
TURES INTERFACE_INCLUDE_DIRECTORIES INTERFACE_LINK_LIBRARIES)

find_package(Protobuf QUIET CONFIG) is required.

If there is "CONFIG" in find_package(), we can get nessary properties.

 Properties for TARGET protobuf::libprotobuf:
   protobuf::libprotobuf.INTERFACE_COMPILE_DEFINITIONS = "PROTOBUF_USE_DLLS"
   protobuf::libprotobuf.INTERFACE_COMPILE_FEA = <NOTFOUND>
   protobuf::libprotobuf.TURES = <NOTFOUND>
   protobuf::libprotobuf.INTERFACE_INCLUDE_DIRECTORIES = "/usr/local/include"
   protobuf::libprotobuf.INTERFACE_LINK_LIBRARIES = "absl::absl_check;absl::absl_log;absl::algorithm;absl::base;absl::bind_front;absl::bits;absl::btree;absl::cleanup;absl::cord;absl::core_headers;absl::debugging;absl::die_if_null;absl::dynamic_annotations;absl::flags;absl::flat_hash_map;absl::flat_hash_set;absl::function_ref;absl::hash;absl::layout;absl::log_initialize;absl::log_severity;absl::memory;absl::node_hash_map;absl::node_hash_set;absl::optional;absl::span;absl::status;absl::statusor;absl::strings;absl::synchronization;absl::time;absl::type_traits;absl::utility;absl::variant"

if NOT...

 Properties for TARGET protobuf::libprotobuf:
   protobuf::libprotobuf.INTERFACE_COMPILE_DEFINITIONS = <NOTFOUND>
   protobuf::libprotobuf.INTERFACE_COMPILE_FEA = <NOTFOUND>
   protobuf::libprotobuf.TURES = <NOTFOUND>
   protobuf::libprotobuf.INTERFACE_INCLUDE_DIRECTORIES = "/usr/local/include"
   protobuf::libprotobuf.INTERFACE_LINK_LIBRARIES = "Threads::Threads"

Now my test code doesn't reference absl-cpp libraries directly. It works well.

mshabunin · 2023-10-12T08:07:18Z

If there is "CONFIG" in find_package(), we can get nessary properties.

As I understood this is related to cmake's built-in protobuf search mechanism. It seem to be using pkg-config and can not correctly add abseil dependencies. Adding CONFIG or NO_MODULE or specifying name protobuf instead of Protobuf disables built-in search mechanism and uses actual cmake package provided by protobuf.

I'm working on an integration testing harness for protobuf, I'll try to provide some solution today or tomorrow.

Kumataro · 2023-10-12T11:12:48Z

I believe it is better to wait your comments/suggestions. Thank you very much !

This problem ,which is related with linking abseil-cpp, is discussed at protocolbuffers/protobuf#12292 (Protobuf Github)

However, it is not resolved clearly, it seems that there are many problems.

I checked what cmake version Ubuntu LTS series uses.

Ubuntu	CMake	protobuf::libprotobuf
14.04	2.8.12.2	N/A
16.04	3.5.1	N/A
18.04	3.10.2	Supported
20.04	3.16.3	Supported

abseil-cpp requires cmake 3.10. and protobuf::libprotobuf is supported after 3.10+. So it is not need to consider about cmake version. ( Before building opencv, to compile protobuf v22+ and abseil-cpp is failed.)

Kumataro · 2023-10-12T13:27:09Z

I intended to maintain the old branch and commit the code without dependence on ABSL to the new branch.

However, I made a mistake updating the same branch. The modifications are as expected. I'm sorry...

mshabunin · 2023-10-12T17:04:04Z

cmake/OpenCVFindProtobuf.cmake

+            if(NOT USED_AFTER_CXX17)
+                message("CMAKE_CXX_STANDARD : ${CMAKE_CXX_STANDARD}")
+                message("protobuf           : ${Protobuf_VERSION}")
+                message(FATAL_ERROR "protobuf(v22 and later) and abseil-cpp request CMAKE_CXX_STANDARD=17 and later.")


Usually OpenCV does not throw errors if an optional dependency can not be found or used - the dependecy just get turned off.
@asmorkalov , @opencv-alalek , what do you think? Should we show a warning and disable protobuf in case of configuration incompatibilty?

Here and below.

Thank you for your review !
I would like to wait for comments for the direction of correction.

And unfortunately, there are some message(FATAL_ERROR) in this file like this block. If error is occured, they will stop configuration.

opencv/modules/dnn/CMakeLists.txt

Lines 133 to 135 in 5199850

if(NOT HAVE_FLATBUFFERS)

message(FATAL_ERROR "DNN: TFLite is not supported without enabled 'flatbuffers'. Check build configuration.")

endif()

opencv/modules/dnn/CMakeLists.txt

Lines 166 to 168 in 5199850

if(cc VERSION_LESS 3.0)

message(FATAL_ERROR "CUDA backend for DNN module requires CC 3.0 or higher. Please remove unsupported architectures from CUDA_ARCH_BIN option or disable OPENCV_DNN_CUDA=OFF.")

endif()

opencv/modules/dnn/CMakeLists.txt

Lines 228 to 230 in 5199850

if(NOT HAVE_OPENVINO AND NOT HAVE_NGRAPH)

message(FATAL_ERROR "DNN: Inference Engine is not supported without enabled 'nGraph'. Check build configuration.")

endif()

It is not a default configuration.
Need to explicitly specify BUILD_PROTOBUF=OFF to go here.
I believe we could these errors here.

Thank you for your review!
Yes, it is clear. This is about protobuf, so I set HAVE_PROTOBUF=OFF if old cxx standard is used. (And I forget C++98 ...)

mshabunin

I've tested this PR using several different protobuf versions (https://github.com/mshabunin/protobuf-check), builds are fine, test had not run.

Overall looks good to me 👍 , except one question.

Kumataro · 2023-10-12T21:10:30Z

Thank you for testing with various protobuf versions!

I also manually verified that there were no problems using the previous version of protobuf (v21), which does not require Abseil-cpp.

Overall looks good to me 👍 , except one question.

I relieve that there were no major problems with this modification.
Thank you very much.

opencv-alalek · 2023-10-13T00:37:41Z

cmake/OpenCVFindProtobuf.cmake

+
+if(HAVE_PROTOBUF)
+    if("${Protobuf_VERSION}" MATCHES [[[0-9]+.([0-9]+).[0-9]+]])
+        string(COMPARE GREATER "${CMAKE_MATCH_1}" "21" REQUEST_AFTER_CXX17)  # >=22


What is the problem with if'(NOT (Protobuf_VERSION VERSION_LESS 22))?

https://cmake.org/cmake/help/latest/command/if.html#version-less

Any non-integer version component or non-integer trailing part of a version component effectively truncates the string at that point.

Yes, It is better than my script. Thank you very much !

opencv-alalek · 2023-10-13T00:38:20Z

cmake/OpenCVFindProtobuf.cmake

+        if(REQUEST_AFTER_CXX17)
+            string(COMPARE GREATER "${CMAKE_CXX_STANDARD}" "16" USED_AFTER_CXX17)  # >=17
+
+            if(NOT USED_AFTER_CXX17)


Use if(GREATER) instead.

This comparing result is used with "NOT", so I use LESS.
And I add to check C++98. Thank you !

opencv-alalek · 2023-10-13T00:42:23Z

cmake/OpenCVFindProtobuf.cmake

+            if(NOT USED_AFTER_CXX17)
+                message("CMAKE_CXX_STANDARD : ${CMAKE_CXX_STANDARD}")
+                message("protobuf           : ${Protobuf_VERSION}")
+                message(FATAL_ERROR "protobuf(v22 and later) and abseil-cpp request CMAKE_CXX_STANDARD=17 and later.")


It is not a default configuration.
Need to explicitly specify BUILD_PROTOBUF=OFF to go here.
I believe we could these errors here.

Kumataro · 2023-10-14T07:06:36Z

cmake/OpenCVFindProtobuf.cmake

  return()
 endif()

+


I'm sorry I have small mistake that is inserting unnecessary blank line.I had created pull request to fix it.

asmorkalov · 2023-10-18T14:07:02Z

@dkurt @opencv-alalek May I merge the patch?

opencv-alalek

LGTM 👍

Supporting protobuf v22 and later(with abseil-cpp/C++17) opencv#24372 fix opencv#24369 related opencv#23791 1. This patch supports external protobuf v22 and later, it required abseil-cpp and c++17. Even if the built-in protobuf is upgraded to v22 or later, the dependency on abseil-cpp and the requirement for C++17 will continue. 2. Some test for caffe required patched protobuf, so this patch disable them. This patch is tested by following libraries. - Protobuf: /usr/local/lib/libprotobuf.so (4.24.4) - abseil-cpp: YES (20230125) ### Pull Request Readiness Checklist See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request - [x] I agree to contribute to the project under Apache 2 License. - [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV - [x] The PR is proposed to the proper branch - [x] There is a reference to the original bug report and related work - [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable Patch to opencv_extra has the same branch name. - [x] The feature is well documented and sample code can be built with the project CMake

Kumataro added 3 commits October 7, 2023 10:11

3rdparty: supporting protobuf v22 and later

41e8e20

dnn: disable some tests for external protobuf

34f5b7b

use GREATER instead of GREATER_EQUAL and remove new blank line at EOF

35c8ea0

Kumataro mentioned this pull request Oct 9, 2023

Build error in OpenCV DNN module: #error "C++ versions less than C++14 are not supported." #23466

Closed

4 tasks

dkurt reviewed Oct 9, 2023

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dkurt reviewed Oct 9, 2023

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fix for review

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dkurt requested a review from mshabunin October 9, 2023 13:15

opencv-alalek added category: build/install category: dnn category: 3rdparty labels Oct 10, 2023

opencv-alalek added this to the 4.9.0 milestone Oct 10, 2023

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fix for BUILD_TESTS=OFF

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mshabunin reviewed Oct 11, 2023

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Use Config mode in CMake.

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mshabunin reviewed Oct 12, 2023

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opencv-alalek reviewed Oct 13, 2023

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fix for review

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mshabunin approved these changes Oct 13, 2023

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Remove unnecessary blank line additions

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Kumataro commented Oct 14, 2023

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shr-project approved these changes Oct 16, 2023

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dkurt approved these changes Oct 18, 2023

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asmorkalov merged commit 6e4280e into opencv:4.x Oct 19, 2023

asmorkalov mentioned this pull request Nov 3, 2023

(5.x) Merge 4.x #24486

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asmorkalov mentioned this pull request Dec 1, 2023

Fix path to ONNX Runtime include folder #24601

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ConnorBaker mentioned this pull request Jun 24, 2025

opencv4: protobuf_21 -> protobuf NixOS/nixpkgs#419335

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mshabunin mentioned this pull request Jul 18, 2025

OpenCV does not support protobuf 3.x #23791

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	if(NOT HAVE_FLATBUFFERS)
	message(FATAL_ERROR "DNN: TFLite is not supported without enabled 'flatbuffers'. Check build configuration.")
	endif()

	if(cc VERSION_LESS 3.0)
	message(FATAL_ERROR "CUDA backend for DNN module requires CC 3.0 or higher. Please remove unsupported architectures from CUDA_ARCH_BIN option or disable OPENCV_DNN_CUDA=OFF.")
	endif()

	if(NOT HAVE_OPENVINO AND NOT HAVE_NGRAPH)
	message(FATAL_ERROR "DNN: Inference Engine is not supported without enabled 'nGraph'. Check build configuration.")
	endif()

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Kumataro commented Oct 8, 2023

Pull Request Readiness Checklist

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Kumataro commented Oct 9, 2023 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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How to install external protobuf v24 and abseil-cpp at Ubuntu 23.04.

To test building opencv4 with options.

If no patch, there are following errors.

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shr-project commented Oct 10, 2023

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Kumataro commented Oct 12, 2023

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asmorkalov commented Oct 18, 2023

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Kumataro commented Oct 9, 2023 •

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