[C++] C++20 modernization

[pitrou]

Describe the enhancement requested

Now that the Arrow C++ codebase is allowed to use C++20 features (at least those are supported on our CI platforms...), we can modernize the codebase a bit. Let's open sub-issues for each individual item.

Component(s)

C++

[pitrou]

@mapleFU

[HuaHuaY]

It seems that some ci environments do not support #include <format> or std::views::join. For examples:

• <format>: https://github.com/apache/arrow/actions/runs/21817350381/job/62941834858
• std::views::join: https://github.com/apache/arrow/actions/runs/21817350381/job/62941834846

I think there may be the following reasons:

• Need higher gcc version. Or clang uses libstdc++ instead of libc++, and these functions requires for higher gcc version.
• Need higher clang version, or need to add -fexperimental-library. https://stackoverflow.com/questions/73929080/error-with-clang-15-and-c20-stdviewsfilter

---

Update some code that can't be compiled:

• iterator-pair std::span constructor: GH-50636: [C++] Replace std::span/ranges usage to fix macOS CRAN #50705 (comment)
• std::ranges: GH-50636: [C++] Replace std::span/ranges usage to fix macOS CRAN #50705 (comment). It should be placed below #if defined(__cpp_lib_ranges) && __cpp_lib_ranges >= 201911L.
• std::bit_cast: https://github.com/apache/arrow/actions/runs/30922874009/job/92037680928
• std::strong_order of float/double: https://github.com/apache/arrow/actions/runs/30975844656/job/92209544116
• emplace_back struct which doesn't have explicit constructor: https://github.com/apache/arrow/actions/runs/32364618433/job/96411331893

[pitrou]

It seems that some ci environments do not support #include <format> or std::views::join. For examples:

Ah, too bad. We'll have to stick with our current idioms then.