Canonical way of handling using a higher version than the minimum for a project?

[Cazadorro]

I have an executable that I wish I use c++23 with. My dependencies are custom local ports, some with minimum versions of c++17 with convenience changes for c++20, others with c++20, but optional changes to expanding interface using c++23. The later cases includes a std variant with a float16 type, so is not compatible with just forcing the executable to be c++23. I would like to force these dependencies to be able to take advantage of newer versions. I tried setting the version in my cmake cache before even setting the cmake toolchain file but that didn't work.

I looked up online but it was excruciating finding any kind of standard practice here. I saw something from a long time ago claiming I could make my own toolchain and force the version there, but that sounds obnoxious, and if that was the expected solution there's zero way there wouldn't be a way to deal with that at the vcpkg configuration level instead, so I don't know if that makes sense to do.

The other thing I saw were people claiming (with out examples of this in practice) that you might use features instead to handle this, so I would enable the c++20 feature and c++23 feature respectively. Because these features are additive in the ports I'm talking about this might make sense but Im wary of doing this because I haven't seen prior art or official recommendations to do this.

[Osyotr]

The canonical way to set global compiler-related flags is to set them in a toolchain file.
If you don't want to write your own toolchain you can use convenience variables provided by default vcpkg toolchains: VCPKG_C_FLAGS and VCPKG_CXX_FLAGS.
Note that vcpkg toolchain is not your project toolchain so you have to set flags in both places.

[Cazadorro]

Note that vcpkg toolchain is not your project toolchain so you have to set flags in both places.

You just mean I'd have to set CMAKE_CXX_STANDARD to 23 and not just VCPKG_CXX_FLAGS to -std=c++23 (for example in a CMakePresets.json)

The canonical way to set global compiler-related flags is to set them in a toolchain file.

You mean I'd make something like a x64-linux-cpp23.cmake file and then put

set(VCPKG_TARGET_ARCHITECTURE x64)
set(VCPKG_CRT_LINKAGE dynamic)
set(VCPKG_LIBRARY_LINKAGE static)

set(VCPKG_CMAKE_SYSTEM_NAME Linux)
set(VCPKG_CXX_FLAGS -std=c++23)

in there?

[Osyotr]

Yes to both questions.