clickhouse-cpp/2.5.1 Conan package fails to build with GCC 11

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Summary

After the recent ConanCenter update of the clickhouse-cpp/2.5.1 recipe (as shown on the ConanCenter page, last updated 2025‑11‑17), building clickhouse-cpp/2.5.1 from source via Conan fails with GCC 11 and C++20.

The main error is:

• use of std::memory_order::memory_order_relaxed instead of std::memory_order_relaxed in types.cpp

Additionally, there is another build failure due to a deprecated enum‑enum bitwise operation being treated as an error (-Werror).

Downgrading to clickhouse-cpp/2.5.0 makes the issue disappear, so this seems to be a regression in the 2.5.1 Conan recipe / sources.

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Environment

• OS: Linux x86_64
• Compiler: GCC 11
• C++ standard: gnu20 (profile compiler.cppstd=gnu20)
• Conan client: 2.x (using conancenter remote)
• Package: clickhouse-cpp/2.5.1 from ConanCenter
• Consumer project uses:
  • conanfile.py with self.requires("clickhouse-cpp/2.5.1")
  • Profile sets compiler.libcxx=libstdc++11, build_type=Release

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Conan profile (relevant parts)

[settings]
arch=x86_64
build_type=Release
compiler=gcc
compiler.version=11
compiler.cppstd=gnu20
compiler.libcxx=libstdc++11
os=Linux

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Steps to reproduce

1. Create a minimal conanfile.py:

   from conan import ConanFile

   class TestClickhouseCpp(ConanFile):
   settings = "os", "compiler", "build_type", "arch"
   generators = "CMakeDeps", "CMakeToolchain"

   def requirements(self):
       self.requires("clickhouse-cpp/2.5.1")
   

2. Run:

   conan install . --output-folder=build/conan_files --build=missing

3. Let Conan download and build clickhouse-cpp/2.5.1 from ConanCenter.

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Actual behavior

The build fails in the clickhouse-cpp sources.

Key errors (paths are Conan’s build folder):

/home//.conan2/p/b/click6c1a182889a69/b/src/clickhouse/types/types.cpp: In member function ‘uint64_t clickhouse::Type::GetTypeUniqueId() const’:
/home//.conan2/p/b/click6c1a182889a69/b/src/clickhouse/types/types.cpp:164:57: error: ‘memory_order_relaxed’ is not a member of ‘std::memory_order’
164 | if (type_unique_id_.load(std::memory_order::memory_order_relaxed) == 0) {
| ^~~~~~~~~~~~~~~~~~~~
/home//.conan2/p/b/click6c1a182889a69/b/src/clickhouse/types/types.cpp:166:112: error: ‘memory_order_relaxed’ is not a member of ‘std::memory_order’
166 | type_unique_id_.store(CityHash64WithSeed(name.c_str(), name.size(), code_), std::memory_order::memory_order_relaxed);
| ^~~~~~~~~~~~~~~~~~~~

From the same build, another error:

/home//.conan2/p/b/click6c1a182889a69/b/src/clickhouse/columns/lowcardinality.cpp: In member function ‘virtual void clickhouse::ColumnLowCardinality::SaveBody(clickhouse::OutputStream*)’:
/home//.conan2/p/b/click6c1a182889a69/b/src/clickhouse/columns/lowcardinality.cpp:344:88: error: bitwise operation between different enumeration types ‘{anonymous}::IndexType’ and ‘{anonymous}::IndexFlag’ is deprecated [-Werror=deprecated-enum-
enum-conversion]
344 | const uint64_t index_serialization_type = indexTypeFromIndexColumn(*index_column_) | IndexFlag::HasAdditionalKeysBit;
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1plus: all warnings being treated as errors
make[2]: *** [clickhouse/CMakeFiles/clickhouse-cpp-lib.dir/columns/lowcardinality.cpp.o] Error 1

Full CMake/Make invocation is driven by Conan; the key point is that warnings are treated as errors and the deprecated enum‑enum bitwise OR becomes a hard error.

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Expected behavior

• clickhouse-cpp/2.5.1 builds successfully with GCC 11 and C++20 (and typical -Werror settings) via ConanCenter.
• No misuse of std::memory_order.

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Analysis

1. Invalid use of std::memory_order

   In src/clickhouse/types/types.cpp the code currently uses:

   if (type_unique_id_.load(std::memory_order::memory_order_relaxed) == 0) {
   const auto name = GetName();
   type_unique_id_.store(
   CityHash64WithSeed(name.c_str(), name.size(), code_),
   std::memory_order::memory_order_relaxed
   );
   }

   But in standard C++ (since C++11):

   • std::memory_order is the enum type.
   • Enumerators are std::memory_order_relaxed, std::memory_order_acquire, etc., in namespace std, not as nested names inside the enum.

   The correct usage should be:

   if (type_unique_id_.load(std::memory_order_relaxed) == 0) {
   const auto name = GetName();
   type_unique_id_.store(
   CityHash64WithSeed(name.c_str(), name.size(), code_),
   std::memory_order_relaxed
   );
   }

   With this change, GCC 11 accepts the code.

2. Deprecated enum bitwise OR with -Werror

   In src/clickhouse/columns/lowcardinality.cpp:

   const uint64_t index_serialization_type =
   indexTypeFromIndexColumn(*index_column_) | IndexFlag::HasAdditionalKeysBit;

   indexTypeFromIndexColumn returns an IndexType, and IndexFlag is a different enum. GCC 11 (with C++20 and current warning settings) warns:

   bitwise operation between different enumeration types … is deprecated

   Because warnings are treated as errors, this stops the build. One way to avoid this is to explicitly cast to an integer type before the bitwise operation, for example:

   const uint64_t index_serialization_type =
   static_cast<uint64_t>(indexTypeFromIndexColumn(*index_column_)) |
   static_cast<uint64_t>(IndexFlag::HasAdditionalKeysBit);

———

Workaround

As a temporary workaround on the consumer side, downgrading to clickhouse-cpp/2.5.0 in conanfile.py:

self.requires("clickhouse-cpp/2.5.0")

allows conan install ... to complete successfully in the same environment.

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Request

• Please fix the std::memory_order::memory_order_relaxed usage to std::memory_order_relaxed in types.cpp.
• Please also consider adjusting the enum bitwise operation in lowcardinality.cpp (or relaxing the relevant warning) so that the library builds cleanly with modern compilers and -Werror.

[simsicon]

I believe 2.6.0 has fixed the issue

Portability fix: renamed deprecated std::memory_order::memory_order_relaxed to std::memory_order_relaxed #343 by @georgthegreat

but conan repo remains 2.5.1 with the buggy version, can anyone update the version on conan?
https://conan.io/center/recipes/clickhouse-cpp?version=2.5.1

[egorsavkin-plb]

I think latest 2.6.1 still has this issue, but in different place:

/.../github.com/ClickHouse/clickhouse-cpp/clickhouse-cpp-2.6.1/clickhouse/columns/lowcardinality.cpp: In member function ‘virtual void clickhouse::ColumnLowCardinality::SaveBody(clickhouse::OutputStream*)’:
/.../github.com/ClickHouse/clickhouse-cpp/clickhouse-cpp-2.6.1/clickhouse/columns/lowcardinality.cpp:399:88: error: bitwise operation between different enumeration types ‘{anonymous}::IndexType’ and ‘{anonymous}::IndexFlag’ is deprecated [-Werror=deprecated-enum-enum-conversion]
  399 |     const uint64_t index_serialization_type = indexTypeFromIndexColumn(*index_column_) | IndexFlag::HasAdditionalKeysBit;
      |                                               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Happened on gcc-15, with such configuration:

        cmake \
            -D BUILD_SHARED_LIBS=ON \
            -D WITH_OPENSSL=ON \
            -D WITH_SYSTEM_ABSEIL=ON \
            -D WITH_SYSTEM_LZ4=OFF \
            -D WITH_SYSTEM_CITYHASH=OFF \
            -D WITH_SYSTEM_ZSTD=ON \
            -D OPENSSL_ROOT_DIR=$CPP_OPENSSL_INSTALL_PATH/.dist \
            -D CMAKE_PREFIX_PATH="$CPP_ABSEILCPP_INSTALL_PATH/.dist;$CPP_ZSTD_INSTALL_PATH/.dist" \
            -D CMAKE_CXX_STANDARD=23 \
            -D CMAKE_CXX_FLAGS="-Wno-deprecated-enum-enum-conversion" \
            -D CMAKE_POSITION_INDEPENDENT_CODE=ON \
            -D CMAKE_SKIP_INSTALL_RPATH=TRUE \
            -D CMAKE_INSTALL_PREFIX=$CPP_CLICKHOUSE_CPP_INSTALL_PATH/.dist \
            ..; \

Changing to CMAKE_CXX_STANDARD=20 doesn't resolve the issue. Only the line -D CMAKE_CXX_FLAGS="-Wno-deprecated-enum-enum-conversion" does.

My system - RHEL-9 like linux, arm64.