Mutually forward-declared types used in templates cause incomplete-type errors in Kendra

[BwL1289]

Describe the bug

When building the AWS SDK w/ C++23, compilation fails due to incomplete types being used in template expressions in the Kendra client that result in error: arithmetic on a pointer to an incomplete type

Specifically, the following two model classes reference each other only via forward declarations:

• DocumentAttributeValueCountPair
• FacetResult

The current workaround is to downgrade to c++17.

Related:

• Kinesis Application Fails to Compile with error incomplete type instantiation #441
• Build error: Incomplete type 'Aws::FSx::Model::AdministrativeAction' used in type trait expression #1397

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

Compilation to succeed

Current Behavior

Compilation crashes with

/opt/llvm_toolchain/bin/../include/c++/v1/__vector/vector.h:1103:5: error: arithmetic on a pointer to an incomplete type 'Aws::kendra::Model::DocumentAttributeValueCountPair'
 1103 |     ++__end;
      |     ^ ~~~~~
/opt/llvm_toolchain/bin/../include/c++/v1/__vector/vector.h:446:90: note: in instantiation of function template specialization 'std::vector<Aws::kendra::Model::DocumentAttributeValueCountPair>::emplace_back<Aws::kendra::Model::DocumentAttributeValueCountPair>' requested here
  446 |   _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI void push_back(value_type&& __x) { emplace_back(std::move(__x)); }
      |                                                                                          ^
/tmp/eugo/aws-sdk-cpp-1.11.453/generated/src/aws-cpp-sdk-kendra/include/aws/kendra/model/FacetResult.h:85:192: note: in instantiation of member function 'std::vector<Aws::kendra::Model::DocumentAttributeValueCountPair>::push_back' requested here
   85 |     inline FacetResult& AddDocumentAttributeValueCountPairs(DocumentAttributeValueCountPair&& value) { m_documentAttributeValueCountPairsHasBeenSet = true; m_documentAttributeValueCountPairs.push_back(std::move(value)); return *this; }
      |                                                                                                                                                                                                ^
/tmp/eugo/aws-sdk-cpp-1.11.453/generated/src/aws-cpp-sdk-kendra/include/aws/kendra/model/FacetResult.h:28:9: note: forward declaration of 'Aws::kendra::Model::DocumentAttributeValueCountPair'
   28 |   class DocumentAttributeValueCountPair;
      |         ^
In file included from /tmp/eugo/aws-sdk-cpp-1.11.453/eugo_build/generated/src/aws-cpp-sdk-kendra/ub_KENDRA.cpp:2:
In file included from /tmp/eugo/aws-sdk-cpp-1.11.453/generated/src/aws-cpp-sdk-kendra/source/KendraEndpointProvider.cpp:6:
In file included from /tmp/eugo/aws-sdk-cpp-1.11.453/generated/src/aws-cpp-sdk-kendra/include/aws/kendra/KendraEndpointProvider.h:8:
In file included from /tmp/eugo/aws-sdk-cpp-1.11.453/src/aws-cpp-sdk-core/include/aws/core/client/GenericClientConfiguration.h:9:
In file included from /tmp/eugo/aws-sdk-cpp-1.11.453/src/aws-cpp-sdk-core/include/aws/core/client/ClientConfiguration.h:9:
In file included from /tmp/eugo/aws-sdk-cpp-1.11.453/src/aws-cpp-sdk-core/include/aws/core/http/Scheme.h:10:
In file included from /tmp/eugo/aws-sdk-cpp-1.11.453/src/aws-cpp-sdk-core/include/aws/core/utils/memory/stl/AWSString.h:12:
In file included from /opt/llvm_toolchain/bin/../include/c++/v1/functional:552:
In file included from /opt/llvm_toolchain/bin/../include/c++/v1/__functional/boyer_moore_searcher.h:25:
/opt/llvm_toolchain/bin/../include/c++/v1/__vector/vector.h:1109:18: error: arithmetic on a pointer to an incomplete type 'Aws::kendra::Model::DocumentAttributeValueCountPair'
 1109 |   return *(__end - 1);
      |            ~~~~~ ^
/tmp/eugo/aws-sdk-cpp-1.11.453/generated/src/aws-cpp-sdk-kendra/include/aws/kendra/model/FacetResult.h:28:9: note: forward declaration of 'Aws::kendra::Model::DocumentAttributeValueCountPair'
   28 |   class DocumentAttributeValueCountPair;
      |         ^
15 errors generated.
ninja: build stopped: subcommand failed.

Reproduction Steps

Build from sources with C++20 or C++23. For example:

cmake .. \
  -DCMAKE_COMPILE_WARNING_AS_ERROR=OFF \
  -DCMAKE_LINK_WARNING_AS_ERROR=OFF \
  -DCMAKE_EXPORT_COMPILE_COMMANDS=ON \
  -DCMAKE_MESSAGE_LOG_LEVEL=debug \
  -DCMAKE_COLOR_DIAGNOSTICS=ON \
  -DCMAKE_BUILD_TYPE=Release \
  -DCMAKE_C_STANDARD='17' \
  -DCMAKE_C_EXTENSIONS=ON \
  -DCMAKE_CXX_STANDARD='23' \
  -DCMAKE_CXX_EXTENSIONS=ON \ 
  -DCPP_STANDARD="23" \
  -DCMAKE_INSTALL_PREFIX="/usr/local" \
  -DBUILD_SHARED_LIBS=ON \
  -DFORCE_SHARED_CRT=ON \
  -DIN_SOURCE_BUILD=OFF \
  -DLEGACY_BUILD=ON \
  -DENABLE_UNITY_BUILD=ON \
  -DMINIMIZE_SIZE=OFF \
  -DSIMPLE_INSTALL=ON \
  -DREGENERATE_CLIENTS=OFF \
  -DREGENERATE_DEFAULTS=OFF \
  -DUSE_CRT_HTTP_CLIENT=OFF \
  -DENABLE_RTTI=ON

Possible Solution

No response

Additional Information/Context

No response

AWS CPP SDK version used

1.11.453

Compiler and Version used

Clang 20.0.0git

Operating System and version

Amz Linux 2023 (aarch64 Fedora based)