Annex C (informative) Compatibility [diff]

Change: New headers.

Rationale: New functionality.

Effect on original feature: The following C++ headers are new: <barrier>, <bit>, <charconv>, <compare>, <concepts>, <coroutine>, <format>, <latch>, <numbers>, <ranges>, <semaphore>, <source_location>, <span>, <stop_token>, <syncstream>, and <version>.

Valid C++ 2017 code that #includes headers with these names may be invalid in this revision of C++.

Change: Remove vacuous C++ header files.

Rationale: The empty headers implied a false requirement to achieve C compatibility with the C++ headers.

Effect on original feature: A valid C++ 2017 program that #includes any of the following headers may fail to compile: <ccomplex>, <ciso646>, <cstdalign>, <cstdbool>, and <ctgmath>.

To retain the same behavior:

• (2.1)
  a #include of <ccomplex> can be replaced by a #include of <complex>,
• (2.2)
  a #include of <ctgmath> can be replaced by a #include of <cmath> and a #include of <complex>, and
• (2.3)
  a #include of <ciso646>, <cstdalign>, or <cstdbool> can simply be removed.