CUDA detection reports "CUDA not found" when nvcc fails due unsupported host GCC

[VenRoot]

Is there an existing issue for this?

• I have searched the existing issues

Is your issue described in the documentation?

• I have read the documentation

Is your issue present in the latest beta/pre-release?

This issue is present in the latest pre-release

Describe the Bug

On Arch Linux, building Sunshine with CUDA enabled fails with:

-- Looking for a CUDA compiler
-- Looking for a CUDA compiler - NOTFOUND
CMake Error at cmake/compile_definitions/linux.cmake:62 (message):
CUDA not found.

If this is intentional, set '-DSUNSHINE_ENABLE_CUDA=OFF' or '-DCUDA_FAIL_ON_MISSING=OFF'

However CUDA is installed and nvcc exists:

/opt/cuda/bin/nvcc
Cuda compilation tools, release 13.2, V13.2.78

The actual failure in CMakeConfigureLog.yaml is that nvcc invokes the system GCC 16 host compiler:

Compiler: /opt/cuda/bin/nvcc
"/usr/bin"/g++ ...
--gnu_version=160101
/usr/include/c++/16.1.1/type_traits: error: identifier "char8_t" is undefined

Arch’s cuda 13.2.1-3 depends on gcc15, and the check succeeds when CMake/nvcc are given:

-DCMAKE_CUDA_COMPILER=/opt/cuda/bin/nvcc
-DCMAKE_CUDA_HOST_COMPILER=/usr/bin/g++-15

Expected Behavior

If check_language(CUDA) fails because nvcc cannot compile with the selected host compiler, the error should mention that CUDA was found but the CUDA compiler test failed, and suggest setting CMAKE_CUDA_HOST_COMPILER / CUDAHOSTCXX.

Actual behavior

The build reports only CUDA not found, which makes it look like the CUDA toolkit is missing.

Additional Context

Environment

• Distro: Garuda Linux (Arch)
• Sunshine: 2026.518.24409.r3.g3a19637
• CUDA package: cuda 13.2.1-3
• Default GCC: gcc 16.1.1
• CUDA-compatible GCC installed: gcc15 15.2.1
• nvcc: /opt/cuda/bin/nvcc, CUDA 13.2.78

Workaround

Passing the CUDA compiler and host compiler explicitly fixes the build:

-DCMAKE_CUDA_COMPILER=/opt/cuda/bin/nvcc
-DCMAKE_CUDA_HOST_COMPILER=/usr/bin/g++-15

Host Operating System

Linux

Operating System Version

Garuda Linux Rolling - Linux 7.0.9

Architecture

amd64/x86_64

Package

Linux - AUR (Third Party)

GPU Type

NVIDIA

GPU Model

RTX 4090

GPU Driver/Mesa Version

595.71.05

Capture Method

None

Apps

Log output

Online logs

No response

[ReenigneArcher]

The errors are generated by CMAKE, not by Sunshine... so nothing we can really do about the how the errors are displayed.

[VenRoot]

The errors are generated by CMAKE, not by Sunshine... so nothing we can really do about the how the errors are displayed.

That makes sense regarding the detailed compiler errors coming from CMake.

The part I was pointing at is the final fatal message, which seems to come from Sunshine itself in cmake/compile_definitions/linux.cmake:

message(FATAL_ERROR
"CUDA not found.
If this is intentional, set '-DSUNSHINE_ENABLE_CUDA=OFF' or '-DCUDA_FAIL_ON_MISSING=OFF'"
)

In my case CUDA/nvcc was present, but CMake’s CUDA compiler check failed because nvcc selected an incompatible host compiler. So the confusing part was that the final message said “CUDA not found”, when the real issue was “CUDA compiler check failed”.

I’m not suggesting Sunshine needs to parse or reformat CMake’s compiler diagnostics. Maybe the Sunshine-side message could just be a little less specific, for example:

CUDA compiler could not be enabled. CUDA may be missing, or nvcc may have failed its compiler check. Check CMakeFiles/CMakeConfigureLog.yaml for the underlying compiler error. If using CUDA with a non-default host compiler, set CMAKE_CUDA_HOST_COMPILER or CUDAHOSTCXX.

That would have made this easier to diagnose while still leaving the detailed error reporting to CMake.

[ReenigneArcher]

It's just an else condition from if(CMAKE_CUDA_COMPILER). Unfortunately we don't have visibility into the reason why CMAKE may set this to false. I don't see value is providing a ton of possible reasons... and this is not really something a user should concern themselves with.

But I'll leave the issue open until we fix the PKGBUILD file to properly force the compiler.