[cfe-dev] clang-tidy and CUDA

[Jakub Klener via cfe-dev]

Hi Richard,

as file names are concerned, I didn't found any information how 
clang-tidy decides in which language the file is written. I made an 
experiment and renamed simple Hello World program hello.cpp to 
hello.frog and then run:

`clang-tidy hello.frog --`

with the Error while processing result. But then I found, that when I invoke

`clang-tidy hello.frog -- -xc++`

everything works fine. So it means, that clang-tidy doesn't support cuda 
files. Below is simple cuda program listing:

```
// simple_add.cu

#include <algorithm>
#include <cmath>
#include <iostream>
#include <memory>


__global__
void add(float *x, const float *y, int n) {
     int index =  blockIdx.x * blockDim.x + threadIdx.x;

     // stride for grid size loop, so the kernel can be run with less 
threads then
     // the sample size
     int stride = blockDim.x * gridDim.x;

     for (int i = index; i < n; i += stride) {
         x[i] = y[i] + x[i];
     }
}

int main(int argc, char** argv) {
     const int N = 1 << 20;

     const float val_x = 1.0f;
     const float val_y = 2.0f;
     // host memory initialization
     std::unique_ptr<float[]> x{new float[N]};
     std::unique_ptr<float[]> y{new float[N]};
     std::fill(x.get(), x.get() + N, val_x);
     std::fill(y.get(), y.get() + N, val_y);

     // device memory initialization
     float *d_x, *d_y;
     cudaMalloc((void**)&d_x, N * sizeof(float));
     cudaMalloc((void**)&d_y, N * sizeof(float));

     // copy to device
     cudaMemcpy(d_x, x.get(), N * sizeof(float), cudaMemcpyHostToDevice);
     cudaMemcpy(d_y, y.get(), N * sizeof(float), cudaMemcpyHostToDevice);

     // invoke the kernell
     const int blockSize = 256;
     const int numBlocks = (N + blockSize - 1) / blockSize;
     add<<<numBlocks, blockSize>>>(d_x, d_y, N);

     // copy out data from device
     cudaMemcpy(x.get(), d_x, N * sizeof(float), cudaMemcpyDeviceToHost);

     // check output validity
     const float mean = val_x + val_y;
     float max_error = std::fabs(*std::max_element(x.get(), x.get() + 100,
             [](const float &a, const float &b) { return std::fabs(a - 
mean) < std::fabs(b - mean); }) - mean);
     std::cout << "Max error: " << max_error << std::endl;

     // free device memory
     cudaFree(d_x);
     cudaFree(d_y);

     return 0;
}
```

It can be compiled by nvcc:
`nvcc -o simple_add -std=c++11 simple_add.cu`
or by clang:
`clang-tidy simple_add.cu -- clang++ -o simple_add simple_add.cu 
-std=c++11 -L/usr/local/cuda/lib64 -lcudart_static -ldl -lrt -pthread`

but clang-tidy issued by
`clang-tidy simple_add.cu -- nvcc -o simple_add -std=c++11` simple_add.cu
or
`clang-tidy simple_add.cu -- clang++ -o simple_add -std=c++11 
-L/usr/local/cuda/lib64 -lcudart_static -ldl -lrt -pthread simple_add.cu`
reports "Error while processing simple_add.cu."

As can be seen from the above, clang can compile CUDA but clang-tidy 
doesn't handle it. Is there any chance to support CUDA in clang-tidy in 
near future?

Versions of used software:
Ubuntu 16.04
clang 6.0.1 with libstdc++ + cuda 8.0
gcc 5.4.0 with cuda 9.2

Jakub

-----Original Message-----
Subject: Re: [cfe-dev] clang-tidy and CUDA
Sent: Wednesday, 4, 7. 2018 11:44
From: cfe-dev at lists.llvm.org
To: cfe-dev at lists.llvm.org
> [Please reply *only* to the list and do not include my email directly
> in the To: or Cc: of your reply; otherwise I will not see your reply.
> Thanks.]
>
> In article <a8b5d138-3a78-de72-181a-5271fec64a47 at eyen.eu>,
>      Jakub Klener via cfe-dev <cfe-dev at lists.llvm.org> writes:
>
>> is it somehow possible to specify source file extension for clang-tidy,
>> can it for example parse ".cu" files? Is there some support for CUDA in
>> clang-tidy? I ran it on my CUDA source file (which I have to rename to
>> ".cc" file because otherwise clang-tidy could not find it), specified
>> -D__CUDACC__, and it found error: unknown type
>> name '__host__' [clang-diagnostic-error].
> Are you using a compilation database or a command-line?
>
> Either way, more information about exactly how you are invoking
> clang-tidy is needed.  AFAIK, clang-tidy doesn't care about the actual
> filename.

* Jakub Klener
* Eyen SE
* Pocernicka 272/96
* 108 00 Prague
* Czech Republic
* http://www.eyen.eu/

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