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# cuda

C+ bindings for the CUDA runtime (`cuda_runtime_api.h`) and cuBLAS (`cublas.h`),
generated by `cpc-bindgen --cpackage` (see `Cplus.toml` for the reproduce
line). The modules are generated: never edit them; regenerate.

```cplus
import "cuda/cuda_runtime_api" as cuda;

var count: i32 = 0;
let rc: i32 = cuda::cudaGetDeviceCount(#addr_of(count));
```

## Linking

`[link] search-paths` is `${CUDA_LIB:-/usr/local/cuda/lib64}`: set `CUDA_LIB`
to the toolkit's library directory when it is anywhere else.

- **Linux**: `/usr/local/cuda/lib64` by default. The directory is also baked
  into the binary as an rpath, so no `LD_LIBRARY_PATH` is needed.
- **Windows**: `CUDA_LIB=%CUDA_PATH%\lib\x64` (for example
  `D:\libraries\cuda-12.6\lib\x64`). A PE image has no rpath: `cudart64_*.dll`
  and `cublas64_*.dll` are found at run time on `PATH` (the CUDA installer puts
  `%CUDA_PATH%\bin` there) or beside the executable.

## Windows modules

`src/*_windows.cplus` shadow the shared modules on Windows (the resolver's
platform override). The shared ones come from the Linux headers and bind
entry points Windows' `cudart.lib` does not export -
`cudaDeviceGetNvSciSyncAttributes` (NvSciSync is Linux/QNX only) - so a
Windows program importing them did not link. The Windows modules are
generated from the Windows toolkit's headers with that symbol skipped:

```
cpc-bindgen --cpackage --out vendor/cuda --variant windows \
  --header %CUDA_PATH%/include/cuda_runtime_api.h --header %CUDA_PATH%/include/cublas.h \
  --clib cudart --clib cublas --skip cudaDeviceGetNvSciSyncAttributes -- -I %CUDA_PATH%/include
```

(generated from CUDA 12.6). Add a `--skip` for any other symbol a Windows
link reports undefined.

`cpc test` here links the runtime and counts devices (`src/test_main.cplus`).
It does not prove the Windows modules are complete: a test build compiles away
wrappers nothing calls, so an unexported symbol only fails an APPLICATION
build that imports the module - build one after regenerating.