[QST] error: non-type template parameters of class type only available with ‘-std=c++20’ or ‘-std=gnu++20’

nvcc --version
nvcc: NVIDIA (R) Cuda compiler driver
Copyright (c) 2005-2025 NVIDIA Corporation
Built on Fri_Feb_21_20:23:50_PST_2025
Cuda compilation tools, release 12.8, V12.8.93
Build cuda_12.8.r12.8/compiler.35583870_0

uname -a
Linux u24 6.14.0-061400-generic #202503241442 SMP PREEMPT_DYNAMIC Mon Mar 24 15:06:01 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux

 g++ --version
g++ (GCC) 14.2.0
Copyright (C) 2024 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

gcc --version
gcc (GCC) 14.2.0
Copyright (C) 2024 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.


git pull
git rev-parse HEAD
62750a2b75c802660e4894434dc55e839f322277

mkdir build
cd build

cmake .. -DCMAKE_CXX_FLAGS="-std=c++20" -DCUTLASS_NVCC_ARCHS="89;120" -DCUTLASS_LIBRARY_KERNELS=all -DCUTLASS_ENABLE_CUBLAS=ON -DCUTLASS_ENABLE_CUDNN=ON -DCMAKE_CUDA_FLAGS="--diag-suppress=1444"

make cutlass_examples -j23

/home/edison/Downloads/cutlass/examples/63_hopper_gemm_with_weight_prefetch/63_hopper_gemm_with_weight_prefetch.cu:199:0:   required from here
  199 | using EpilogueOutputOp  = typename Gemm::EpilogueOutputOp;
/home/edison/Downloads/cutlass/examples/63_hopper_gemm_with_weight_prefetch/collective/sm90_mma_tma_gmma_ss_warpspecialized_with_prefetch.hpp:160:63: error: non-type template parameters of class type only available with ‘-std=c++20’ or ‘-std=gnu++20’
  160 |   using PrefetchSmemLayoutA = decltype(make_layout(make_shape(
      |                                                     ~~~~~~~~~~^
/home/edison/Downloads/cutlass/examples/63_hopper_gemm_with_weight_prefetch/collective/sm90_mma_tma_gmma_ss_warpspecialized_with_prefetch.hpp:160:63: error: non-type template parameters of class type only available with ‘-std=c++20’ or ‘-std=gnu++20’
make[3]: *** [examples/63_hopper_gemm_with_weight_prefetch/CMakeFiles/63_hopper_gemm_with_weight_prefetch.dir/build.make:77: examples/63_hopper_gemm_with_weight_prefetch/CMakeFiles/63_hopper_gemm_with_weight_prefetch.dir/63_hopper_gemm_with_weight_prefetch.cu.o] Error 1
make[2]: *** [CMakeFiles/Makefile2:46639: examples/63_hopper_gemm_with_weight_prefetch/CMakeFiles/63_hopper_gemm_with_weight_prefetch.dir/all] Error 2
make[1]: *** [CMakeFiles/Makefile2:39741: examples/CMakeFiles/cutlass_examples.dir/rule] Error 2
make: *** [Makefile:16450: cutlass_examples] Error 2

I had tried modifed the cmakelist.txt:

#
# CUTLASS 3.x requires C++17
#
set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_CXX_EXTENSIONS OFF)

but still same.

Start with the build command and the CMake standard settings, then inspect examples/63_hopper_gemm_with_weight_prefetch/63_hopper_gemm_with_weight_prefetch.cu and its collective/sm90_mma_tma_gmma_ss_warpspecialized_with_prefetch.hpp header around line 160. Reproduce the cutlass_examples build and trace which flags reach nvcc. Done means the reported example builds successfully with the stated configuration.