# CMake does not find CUDA if not in $PATH if CUDA is a project LANGUAGE
**URL:** https://discourse.cmake.org/t/cmake-does-not-find-cuda-if-not-in-path-if-cuda-is-a-project-language/2790
**Category:** Usage
**Created:** [February 17, 2021, 1:59pm UTC](https://discourse.cmake.org/t/cmake-does-not-find-cuda-if-not-in-path-if-cuda-is-a-project-language/2790 "2021-02-17T13:59:20Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@paskino](https://discourse.cmake.org/u/paskino)
#### Post date: [February 17, 2021, 1:59pm UTC](https://discourse.cmake.org/t/cmake-does-not-find-cuda-if-not-in-path-if-cuda-is-a-project-language/2790/1 "2021-02-17T13:59:20Z")
Dear all,
I am pretty confused: since 3.10 CUDA is a first class language and one need not to use find\_package(CUDA) nor find\_package(CUDAToolkit).
A minimal setup you can find at [https://github.com/paskino/cmake-cuda](https://github.com/paskino/cmake-cuda)
My CMakeLists.txt is:
```
make_minimum_required(VERSION 3.10 FATAL_ERROR)
# THIS IS DEFAULT AND FAILS
project(prova LANGUAGES CUDA)
add_executable(jacobi ${CMAKE_CURRENT_SOURCE_DIR}/example.cu)
```
However, I recently stumbled upon the problem that because nvcc was not found in the $PATH, cmake would fail as
```
-- The CUDA compiler identification is unknown
CMake Error at CMakeLists.txt:2 (project):
No CMAKE_CUDA_COMPILER could be found.
```
Solution to this is to add the path to `nvcc` to `$PATH` or to specify the environment variable `CUDACXX` or pass `-DCMAKE_CUDA_COMPILER`.
If I change my CMakeLists.txt to use the deprecated method CMake finds nvcc and compiles correctly.
```
# THIS IS DEPRECATED AND WORKS PERFECTLY
# project(prova LANGUAGES CXX)
# find_package(CUDA REQUIRED)
# CUDA_ADD_EXECUTABLE(jacobi ${CMAKE_CURRENT_SOURCE_DIR}/example.cu)
```
So in conclusion, if I use the deprecated method CMake works as expected: is able to find a suitable nvcc compiler, while the more modern approach is not able to find nvcc and I have to provide it manually, which I find bizzarre. Probably I’m missing something…
I tried this on a variety of systems, windows and linux with CMake 3.17 or 3.18.
Thanks
Edoardo
---
### Author:  [@ben.boeckel](https://discourse.cmake.org/u/ben.boeckel)
#### Post date: [February 17, 2021, 2:49pm UTC](https://discourse.cmake.org/t/cmake-does-not-find-cuda-if-not-in-path-if-cuda-is-a-project-language/2790/2 "2021-02-17T14:49:58Z")
I don’t think CMake supports finding _just_ the CUDA language. I think one needs C and/or C++ in order to get the system linker information going. @robert.maynard is that true?
---
### Author:  [@paskino](https://discourse.cmake.org/u/paskino)
#### Post date: [February 17, 2021, 2:56pm UTC](https://discourse.cmake.org/t/cmake-does-not-find-cuda-if-not-in-path-if-cuda-is-a-project-language/2790/3 "2021-02-17T14:56:10Z")
You mean changing the `LANGUAGES` line to the following?
```
project(prova LANGUAGES C CXX CUDA)
```
Unfortunately it doesn’t help:
```
cmake ..
-- The C compiler identification is GNU 7.5.0
-- The CXX compiler identification is GNU 7.5.0
-- The CUDA compiler identification is unknown
```
Edoardo
---
### Author:  [@robert.maynard](https://discourse.cmake.org/u/robert.maynard)
#### Post date: [February 17, 2021, 2:59pm UTC](https://discourse.cmake.org/t/cmake-does-not-find-cuda-if-not-in-path-if-cuda-is-a-project-language/2790/4 "2021-02-17T14:59:04Z")
> [@paskino](#):
>
> So in conclusion, if I use the deprecated method CMake works as expected: is able to find a suitable nvcc compiler, while the more modern approach is not able to find nvcc and I have to provide it manually, which I find bizzarre. Probably I’m missing something
The modern approach means that the CUDA language follows CMake default behavior for finding a compiler. This approach searches the system env PATH or the CUDACXX env variable.
Since compiler detection is done as part of platform detection, CMake can’t use `find_` calls during this step, meaning we don’t know about or able to search places such as `/usr/local/cuda/` or can we safely presume `nvcc` is the desired CUDA compiler ( we support `clang` as well ).
> [@ben.boeckel](#):
>
> I don’t think CMake supports finding _just_ the CUDA language. I think one needs C and/or C++ in order to get the system linker information going. @robert.maynard is that true?
CMake fully supports CUDA being the only enabled language.
---
### Author:  [@ben.boeckel](https://discourse.cmake.org/u/ben.boeckel)
#### Post date: [February 17, 2021, 3:04pm UTC](https://discourse.cmake.org/t/cmake-does-not-find-cuda-if-not-in-path-if-cuda-is-a-project-language/2790/5 "2021-02-17T15:04:46Z")
> [@robert.maynard](#):
>
> CMake fully supports CUDA being the only enabled language.
Ah, that’s good to hear.
---
### Author:  [@paskino](https://discourse.cmake.org/u/paskino)
#### Post date: [February 17, 2021, 4:23pm UTC](https://discourse.cmake.org/t/cmake-does-not-find-cuda-if-not-in-path-if-cuda-is-a-project-language/2790/6 "2021-02-17T16:23:27Z")
@robert.maynard are you saying that CMake won’t be able to find the nvcc compiler if it sits in a default location but it’s not in the `PATH`?
I don’t think this is satisfactory. The CUDA Toolkit is not often part of the OS, so it’s binaries may well not be in the `PATH`.
I suppose there is nothing like a free lunch: with the old method it is more difficult to create targets for CUDA, while with the modern approach it’s easy to create targets but more difficult to find the compiler even if it’s in “standard” locations.
Thanks
Edoardo