[BUG]: namespace "std" has no member "is_same_v"

[capybara-club]

Is this a duplicate?

• I confirmed there appear to be no duplicate issues for this bug and that I agree to the Code of Conduct

Type of Bug

Compile-time Error

Component

cuda.core

Describe the bug

I can't seem to get code like

std::is_same_v<T, f32>

to compile. I tried adding #include <cuda/std/type_traits> and that didn't fix it. I have c++17 set.

Any ideas?

How to Reproduce

defget_include_dir_cuda() ->Path:
"""Best-effort guess of the Toolkit’s <cuda>/include directory."""importos, shutilifos.getenv("CUDA_HOME"):
returnPath(os.environ["CUDA_HOME"]) /"include"# fall back to the directory that owns nvcc (works for most local installs)nvcc=shutil.which("nvcc")
ifnvcc:
returnPath(nvcc).parent.parent/"include"raiseRuntimeError("Cannot find CUDA include directory")
code=r""" #include <cuda/std/type_traits> extern "C" __global__  void  hello() { static_assert(std::is_same_v<float, float>); printf("hello from device\n"); } """dev=Device()
dev.set_current()
s=dev.create_stream()
arch="".join(f"{i}"foriindev.compute_capability)
print(f'arch:{arch}')
print(get_include_dir_cuda())
# Compile cuda to ptxmodule_ptx= \
Program(
code, code_type="c++", options= \
ProgramOptions(
std="c++17", arch=f"sm_{arch}",
include_path=[get_include_dir_cuda()]
)
).compile("ptx", logs=sys.stdout)
print(module_ptx.code.decode())

Expected behavior

Should compile.

Operating System

Ubuntu 24.04

nvidia-smi output

+-----------------------------------------------------------------------------------------+
| NVIDIA-SMI 575.55.01 Driver Version: 576.40 CUDA Version: 12.9 |
|-----------------------------------------+------------------------+----------------------+
| GPU Name Persistence-M | Bus-Id Disp.A | Volatile Uncorr. ECC |
| Fan Temp Perf Pwr:Usage/Cap | Memory-Usage | GPU-Util Compute M. |
| | | MIG M. |
|=========================================+========================+======================|
| 0 NVIDIA GeForce RTX 4090 On | 00000000:01:00.0 On | Off |
| 0% 45C P3 63W / 450W | 2111MiB / 24564MiB | 0% Default |
| | | N/A |
+-----------------------------------------+------------------------+----------------------+
+-----------------------------------------------------------------------------------------+
| Processes: |
| GPU GI CI PID Type Process name GPU Memory |
| ID ID Usage |
|=========================================================================================|
| No running processes found |
+-----------------------------------------------------------------------------------------+

[leofang]

Hi @capybara-club, to use libcudacxx (libcu++) headers we need to use fully qualified names cuda::std::is_same_v. The standard C++ names are not visible to the CUDA online compiler (NVRTC).

[capybara-club]

I see, that change worked immediately!