circle

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The program

int main()
{
  auto device_lambda = [] __device__ () {};
  return 0;
}

Causes circle to emit the error message

$ circle --cuda-path=/usr/local/cuda -sm_50 repro.cu 
error: repro.cu:3:24
error forming list comprehension
  auto device_lambda = [] __device__ () {}; 
                       ^
  error: repro.cu:3:25
  expected 1 or more items in initializer-list
    auto device_lambda = [] __device__ () {}; 

Compiler details:

$ ~/Desktop/circle/circle --version
circle version 1.0.0-136
  Circle public preview build 136
  Built Sep 27 2021 23:42:52
  (c) 2021 Sean Baxter
  https://www.circle-lang.org/
  Twitter: @seanbax

There is no attribute-specifier-seq in that position, by the standard. I do parse attributes after the ( ), (accessible through the lambda-specifiers in the grammar). The error you are seeing is due to the existence of a Python-style list comprehension in Circle. It thinks [] is for the list comprehension, since it doesn't match the lambda grammar as implemented.

If I add attribute-specifier-seq parsing immediately after the lambda-introducer like you show, does this get us anything? This is to compile with existing nvcc code? You definitely don't need/want it with new code. Do you know if nvc++ supports that syntax?

You can leave the device tag off the lambda and it will work when called from the kernel.

Do you know if nvc++ supports that syntax?

Yes, it's a so-called "extended lambda" enabled with --expt-extended-lambda