Failed to build with c++23

[iamfobey]

Hello!

I'm always get error: non-const lvalue reference to type 'cppspmd_sse41::spmd_kernel::vfloat' cannot bind to a temporary of type 'cppspmd_sse41::spmd_kernel::vfloat when I'm trying to build KTX.

In file included from /media/dezlow/Drive/Dev/C++/Oneiro/ThirdParty/KTX/lib/basisu/encoder/basisu_kernels_sse.cpp:41:
/media/dezlow/Drive/Dev/C++/Oneiro/ThirdParty/KTX/lib/basisu/encoder/cppspmd_sse.h:496:10: error: non-const lvalue reference to type 'cppspmd_sse41::spmd_kernel::vfloat' cannot bind to a temporary of type 'cppspmd_sse41::spmd_kernel::vfloat'
                return dst;
                       ^~~
/media/dezlow/Drive/Dev/C++/Oneiro/ThirdParty/KTX/lib/basisu/encoder/cppspmd_sse.h:508:10: error: non-const lvalue reference to type 'cppspmd_sse41::spmd_kernel::vfloat' cannot bind to a temporary of type 'cppspmd_sse41::spmd_kernel::vfloat'
                return dst;
                       ^~~

I'm building my project with using GitHub Actions and I get the same error.

Sorry for my English, lol.

Thanks!

cat /etc/os-release

PRETTY_NAME="Debian GNU/Linux bookworm/sid"
NAME="Debian GNU/Linux"
VERSION_CODENAME=bookworm
ID=debian
HOME_URL="https://www.debian.org/"
SUPPORT_URL="https://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"

clang --version

Debian clang version 14.0.6-2
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin

[MarkCallow]

Our CI builds with clang for macOS, Windows ARM and Emscripten. In addition macOS/Xcode 14 (clang 14.0.29) is my primary development environment. CI also builds on Ubuntu with GCC. Also I know a user who is successfully building with mingw_llvm. The issue is something specific to your situation and therefore not easy for me to debug.

The error appears to be related to the use of && on the dst parameter declaration but why only you are seeing it I have no idea. Please try to debug further yourself.

[MarkCallow]

Changed title because KTX builds fine on Linux with GCC.

[iamfobey]

Our CI builds with clang for macOS, Windows ARM and Emscripten. In addition macOS/Xcode 14 (clang 14.0.29) is my primary development environment. CI also builds on Ubuntu with GCC. Also I know a user who is successfully building with mingw_llvm. The issue is something specific to your situation and therefore not easy for me to debug.
In my solution, I fix this with the following:

return  static_cast<vfloat&>(dst)

And it works fine, but I think it is a bad idea to fix this.

I tried to run PVS studio workflow in my project, but project not compiles and return the same error.
https://github.com/OneiroGames/Oneiro/actions/runs/3643926582/jobs/6152631619#step:4:2190

And video (maybe to be helpful)

simplescreenrecorder-2022-12-09_19.13.35.mp4

[MarkCallow]

Is this still an issue for you in main?

[Flone-dnb]

I just got the same error on Archlinux with Clang 16.

[MarkCallow]

I just got the same error on Archlinux with Clang 16.

On which branch? Which errors?

The latest code compiles via ClangCL both 15 & 16 in VS 2022. It compiles with clang 14 on macOS and clang 17 in Emscripten. I do not have the bandwidth to work on another platform. If you want this fixed I'll need a PR that fixes it. If the errors are in the lib/basisu/* code then the preferred fix is to disable the subject warnings in CMakeLists.txt. If elsewhere in lib then please fix the warnings.

[Flone-dnb]

On which branch? Which errors?

Latest commit from main branch. Same errors as described above.

Changing 2 places in cppspmd_sse.h to:

return static_cast<vfloat&>(dst)

Fixes build.

P.S. With this fix, reading KTX files via libktx seems to work fine, can't tell about other things tho.

[MarkCallow]

I can't debug this or test fixes as my machine is arm64-based so SSE code is never compiled. I made a simple reproducer which I'm compiling with AppleClang 15.0.0. The error appears when compiling with --std=c++2b (i.e. draft c++23).

@Flone-dnb and @DezlowNG are you building with KTX-Software's CMakeLists.txt? Do you have a parent project that is including it? I'm guessing you must somehow be specifying C++23. Looks like I'll need to explicitly specify the c++ standard when compiling the library. First I'll see if I can find a code fix.

[MarkCallow]

I opened an issue upstream: BinomialLLC/basis_universal#366.

[MarkCallow]

Fixed by PR #806.

[Flone-dnb]

@MarkCallow

are you building with KTX-Software's CMakeLists.txt? Do you have a parent project that is including it? I'm guessing you must somehow be specifying C++23

That's right.

I just tried using the latest commit (f8220ec) and I can confirm that everything builds correctly on Linux now.

Thanks.