[C++] Adopt C++17 idioms and features for maintainability

[asfimport]

A first version of this task was attempted one year ago in #10414

Possible idioms to look for:

• if constexpr to replace SFINAE hackery

• std::from_chars and std::to_chars to replace locale-dependent number parsing/formatting

• lambda capture move-construction

  Possibly sub-tasks:

• regenerate Flatbuffers files for C++17 (see build-support/update-flatbuffers.sh)

• update build-support/cpplint.py to newer upstream version

Reporter: Antoine Pitrou / @pitrou

Related issues:

• [C++] Use std::to_chars instead of std::to_string (is a parent of)
• [C++] Regenerate Flatbuffers files for C++17 (is a parent of)
• [C++] Use lambda capture move construction (is a parent of)
• [C++] Use [[nodiscard]] (is a parent of)
• [C++] Use if constexpr in CSV subsystem (is a parent of)
• [C++] Use generic lambdas in arrow/compare.cc (is a parent of)

_{Note: This issue was originally created as ARROW-17547. Please see the migration documentation for further details.}

[asfimport]

Jin Shang / @js8544:
Another possible C++17 idiom is the [[nodiscard]] attribute. Clang-tidy has this check (https://releases.llvm.org/9.0.0/tools/clang/tools/extra/docs/clang-tidy/checks/modernize-use-nodiscard.html) and can be used to apply it automatically.

[asfimport]

Jin Shang / @js8544:
Ah, and also std::make_unique, if C++14 idioms count.

[asfimport]

Antoine Pitrou / @pitrou:
Yes, C++14 idioms do count :-)

[asfimport]

Antoine Pitrou / @pitrou:
Good point about [[nodiscard]], thanks!

[asfimport]

Antoine Pitrou / @pitrou:
Hmm, unfortunately GCC has parser bugs that prohibit the use of [[discard]] with other attributes such as \_\_attribute\_\_ or \_\_declspec. For example here is a failure on MinGW:

D:/a/arrow/arrow/cpp/src/arrow/status.h:132:20: error: expected identifier before '[' token
 132 | class ARROW_EXPORT [[nodiscard]] Status : public util::EqualityComparable<Status>,
 | ^
D:/a/arrow/arrow/cpp/src/arrow/status.h:132:41: error: expected initializer before ':' token
 132 | class ARROW_EXPORT [[nodiscard]] Status : public util::EqualityComparable<Status>,
 | ^
D:/a/arrow/arrow/cpp/src/arrow/status.h:376:32: error: invalid use of incomplete type 'class arrow::Status'
 376 | void Status::MoveFrom(Status& s) {
 | ^

[asfimport]

Jin Shang / @js8544:
I see. Clang-tidy would only add it to member functions, not class declarations though.