novice usage question

[prlw1]

I have a checkout of https://github.com/BobSteagall/wg21.git in /usr/src/local/wg21, and https://github.com/kokkos/mdspan.git in /usr/src/local/mdspan, head from just now. I thought I might start with the staggeringly complex program:

#include <linear_algebra.hpp>

int main() { }

but with g++ 10.3.0, I see:

c++  -O2 -fPIE -g -Werror -std=c++20     -I/usr/src/local/mdspan/include -I/usr/src/local/wg21/include  -c    wg21test.cc
In file included from /usr/src/local/wg21/include/linear_algebra.hpp:62,
                 from wg21test.cc:1:
/usr/src/local/wg21/include/linear_algebra/private_support.hpp:276:27: error: ‘basic_mdspan’ was not declared in this scope
  276 | struct extract_span_types<basic_mdspan<T0, X0, L0, A0>, basic_mdspan<T1, X1, L1, A1>>
      |                           ^~~~~~~~~~~~

What am I missing?

[Twon]

So this is caused by the fact that basic_mdspan has been renamed to mdspan in the Kokkos repository. We are going to address this change in the WG21 LA repo shortly, but for now, this should not cause an issue because we have pinned WG21 LA to using a specific version of the Kokkos repository before this change was made, see here:

wg21/CMakeLists.txt

Line 24 in 51b291a

FetchContent_Declare(mdspan GIT_REPOSITORY https://github.com/kokkos/mdspan.git GIT_TAG 9d1acac543053cbe6839273f550b1ece218e9696)

I've just checked out a clean version of the repository and can confirm this is building for me. Can you please provide more details on the steps you took to generate this error?

• Which OS, Compiler, Architecture are you attempting to build on?
• Do you have the latest version of the code? Was this a clean checkout or updating an existing repo?
• Have you tried deleting the build folder (the Kokkos repository is synced here so deleting this will force a new fetch of the Kokkos repository from scratch (If you have the latest change this should work)
• Are you building from a clone of the Github repo, or using the Conan package?

[prlw1]

Thank you - that is precisely what I was missing.

cd /usr/src/local/mdspan
git checkout 9d1acac54305

and the trivial program compiles.

[Twon]

Great, I'm glad that has solved your issue. I'll close this down for now. Feel free to reopen, or open a new issue if you encounter any further issues.