Bug type
Compile-time Error
Affected component
CUB
Bug description
Commit 1e3b0b4
PR: #6844
("Avoid use of cccl namespace macros in cub") removed _CCCL_BEGIN_NAMESPACE_CUDA /
_CCCL_END_NAMESPACE_CUDA macros and replaced them with inline explicit qualification.
The resulting code in cub/device/device_transform.cuh:44 uses ::cuda:: as the
class-head name in a template specialization:
struct ::cuda::proclaims_copyable_arguments<CUB_NS_QUALIFIER::detail::__return_constant<T>>
: ::cuda::std::true_typeThis is ill-formed C++. The C++ standard forbids a globally-qualified name (::cuda::)
as the class-head name of a struct/class definition or template specialization. The leading
:: is valid in expression and type-specifier contexts, but not in a class-head name.
NVCC on x86 silently accepts this as a non-conforming extension, but GCC on ARM/SBSA
treats it as a hard error, breaking any downstream project that includes <cub/cub.cuh>
when building with CUDA 13.2+ on SBSA.
Error message
cub/device/device_transform.cuh:44:134:
error: global qualification of class name is invalid before ':' token
44 | struct ::cuda::proclaims_copyable_arguments<...> : ::cuda::std::true_type
| ^
error: expected '{' before ':' token
Reproducer
Run the shell script below — it creates two CMake projects and a Dockerfile, then
launches docker build using the exact image that ships the buggy headers.
The good project compiles cleanly; the bad project fails with the GCC error above.
#!/bin/bash
set -e
rm -rf /tmp/cccl_reproducer_bad /tmp/cccl_reproducer_good
mkdir -p /tmp/cccl_reproducer_bad /tmp/cccl_reproducer_good
cat << 'REPRODUCER_BAD_EOF' > /tmp/cccl_reproducer_bad/reproducer.cpp
#include <type_traits>
namespace cuda {
template <typename T>
struct proclaims_copyable_arguments : std::false_type {};
}
namespace detail {
template <typename T> struct __return_constant {};
}
// ill-formed: leading :: forbidden in class-head name
// mirrors cub/device/device_transform.cuh:44 after commit 1e3b0b4
template <typename T>
struct ::cuda::proclaims_copyable_arguments<detail::__return_constant<T>>
: std::true_type {};
int main() {}
REPRODUCER_BAD_EOF
cat << 'REPRODUCER_GOOD_EOF' > /tmp/cccl_reproducer_good/reproducer.cpp
#include <type_traits>
namespace cuda {
template <typename T>
struct proclaims_copyable_arguments : std::false_type {};
}
namespace detail {
template <typename T> struct __return_constant {};
}
// correct: relative qualification in class-head name
// one-character fix: remove leading :: from class-head name
template <typename T>
struct cuda::proclaims_copyable_arguments<detail::__return_constant<T>>
: std::true_type {};
int main() {}
REPRODUCER_GOOD_EOF
cat << 'CMAKE_EOF' > /tmp/cccl_reproducer_bad/CMakeLists.txt
cmake_minimum_required(VERSION 3.20)
project(cccl_reproducer_bad CXX)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
message(STATUS "Compiler: ${CMAKE_CXX_COMPILER_ID} ${CMAKE_CXX_COMPILER_VERSION}")
find_package(CUDA REQUIRED)
add_executable(reproducer reproducer.cpp)
CMAKE_EOF
cat << 'CMAKE_GOOD_EOF' > /tmp/cccl_reproducer_good/CMakeLists.txt
cmake_minimum_required(VERSION 3.20)
project(cccl_reproducer_good CXX)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
message(STATUS "Compiler: ${CMAKE_CXX_COMPILER_ID} ${CMAKE_CXX_COMPILER_VERSION}")
find_package(CUDA REQUIRED)
add_executable(reproducer reproducer.cpp)
CMAKE_GOOD_EOF
cat > /tmp/Dockerfile.cccl_reproducer << 'DOCKERFILE_EOF'
FROM nvcr.io/nvidia/cuda-dl-base:26.04-cuda13.2-devel-ubuntu24.04
COPY ./cccl_reproducer_good /cccl_reproducer_good
COPY ./cccl_reproducer_bad /cccl_reproducer_bad
RUN apt-get update -qq && apt-get install -y cmake build-essential
RUN echo -e "�[32m ==Device Transform Cuh:44-50== �[0m" && echo -e "�[33m $(sed -n '40,50p' /usr/local/cuda/include/cccl/cub/device/device_transform.cuh) �[0m"
WORKDIR /cccl_reproducer_good
RUN cmake -B /cccl_build_good -S /cccl_reproducer_good && cmake --build /cccl_build_good
WORKDIR /cccl_reproducer_bad
RUN cmake -B /cccl_build_bad -S /cccl_reproducer_bad && cmake --build /cccl_build_bad
DOCKERFILE_EOF
docker build --progress=plain -t cccl_reproducer -f /tmp/Dockerfile.cccl_reproducer /tmpSuggested fix
- struct ::cuda::proclaims_copyable_arguments<CUB_NS_QUALIFIER::detail::__return_constant<T>>
+ struct cuda::proclaims_copyable_arguments<CUB_NS_QUALIFIER::detail::__return_constant<T>>
: ::cuda::std::true_typeSame fix applies to any other class-head names introduced by the same commit
that use ::cuda:: or ::cuda::std:: as the leading qualifier.
Environment
|
|
| CCCL version |
Introduced in commit 1e3b0b4, present in CUDA 13.2 |
| Affected file |
cub/device/device_transform.cuh:44 |
| Failing compiler |
GCC 13+ |
| Reproducer image |
nvcr.io/nvidia/cuda-dl-base:26.04-cuda13.2-devel-ubuntu24.04 |
Bug type
Compile-time Error
Affected component
CUB
Bug description
Commit 1e3b0b4
PR: #6844
("Avoid use of cccl namespace macros in cub") removed
_CCCL_BEGIN_NAMESPACE_CUDA/_CCCL_END_NAMESPACE_CUDAmacros and replaced them with inline explicit qualification.The resulting code in
cub/device/device_transform.cuh:44uses::cuda::as theclass-head name in a template specialization:
struct ::cuda::proclaims_copyable_arguments<CUB_NS_QUALIFIER::detail::__return_constant<T>> : ::cuda::std::true_typeThis is ill-formed C++. The C++ standard forbids a globally-qualified name (
::cuda::)as the class-head name of a struct/class definition or template specialization. The leading
::is valid in expression and type-specifier contexts, but not in a class-head name.NVCC on x86 silently accepts this as a non-conforming extension, but GCC on ARM/SBSA
treats it as a hard error, breaking any downstream project that includes
<cub/cub.cuh>when building with CUDA 13.2+ on SBSA.
Error message
Reproducer
Run the shell script below — it creates two CMake projects and a Dockerfile, then
launches
docker buildusing the exact image that ships the buggy headers.The good project compiles cleanly; the bad project fails with the GCC error above.
Suggested fix
Same fix applies to any other class-head names introduced by the same commit
that use
::cuda::or::cuda::std::as the leading qualifier.Environment
cub/device/device_transform.cuh:44nvcr.io/nvidia/cuda-dl-base:26.04-cuda13.2-devel-ubuntu24.04