fix: support clang in meson build

[SignalWalker]

Describe your PR, what does it fix/add?

Fixes an error when building with Clang, which doesn't yet support -std=c++23, and instead uses -std=c++2b.

Is there anything you want to mention? (unchecked code, possible bugs, found problems, breaking compatibility, etc.)

Tested with Clang 14.0.6 and GCC 12.1.1.

Ideally, someone will replace this with default_options : [ ..., 'cpp_std=c++23' ] once Meson supports that.

Is it ready for merging, or does it need work?

👍

[viperML]

Maybe we could fix this warning instead:

meson.build:14: WARNING: Consider using the built-in option for language standard version instead of using "-std=c++23"

[vaxerski]

Does clang actually compile Hyprland? it didnt want to iirc a while ago

[viperML]

https://github.com/viperML/Hyprland/actions/runs/2848249132

It doesn't seem like at first glance (standard builds failed when trying to push to cache)

[SignalWalker]

Maybe we could fix this warning instead:

meson.build:14: WARNING: Consider using the built-in option for language standard version instead of using "-std=c++23"

Meson only supports that flag with C++ <= 20 right now, and Hyprland seems to require C++23. This is why I wrote it to use has_argument instead of project(default_options).

https://github.com/viperML/Hyprland/actions/runs/2848249132

It doesn't seem like at first glance (standard builds failed when trying to push to cache)

Clang uses libc++ by default (instead of libstdc++). std::unreachable() was added to libc++ in version 15. Nixpkgs's LLVM stdenv derivations clamp their libc++ versions to that of their corresponding Clang binary. The latest version of Clang available in Nixpkgs is v14.0.6, so the latest version of libc++ in Nixpkgs is v14.0.6.

Those builds failed because you ran them with llvmPackages_12 and llvmPackages_13, which don't provide versions of libc++ recent enough to have std::unreachable(). To get Clang to build Hyprland in Nix, you'd need something like llvmPackages_15, which doesn't yet exist in Nixpkgs.

[fufexan]

If it does build in clang fine, I'd say this is ready to merge. We'll be using GCC in the Nix builds anyway. Not sure if there's a benefit to using Clang instead but I'll be happy to hear it out if there is.

[SignalWalker]

If it does build in clang fine, I'd say this is ready to merge. We'll be using GCC in the Nix builds anyway. Not sure if there's a benefit to using Clang instead but I'll be happy to hear it out if there is.

Honestly it's mostly just because I have CC=clang and CXX=clang++ set and it was making yay -Syu fail when updating Hyprland. I just like Clang's UI more.

[vaxerski]

ok