libstdc++: Add code comment documenting LWG 4027 change [PR118083]

Patrick Palka · Patrick Palka · commit 640697f7c2de · 2025-02-26T14:51:38.000-05:00
PR libstdc++/118083

libstdc++-v3/ChangeLog:

	* include/bits/ranges_base.h
	(ranges::__access::__possibly_const_range): Mention LWG 4027.
diff --git a/libstdc++-v3/include/bits/ranges_base.h b/libstdc++-v3/include/bits/ranges_base.h
@@ -646,6 +646,8 @@ namespace ranges
       constexpr auto&
       __possibly_const_range(_Range& __r) noexcept
       {
+	// _GLIBCXX_RESOLVE_LIB_DEFECTS
+	// 4027. possibly-const-range should prefer returning const R&
 	if constexpr (input_range<const _Range>)
 	  return const_cast<const _Range&>(__r);
 	else

Original file line number	Diff line number	Diff line change
`@@ -646,6 +646,8 @@ namespace ranges`
`646`	`646`	`constexpr auto&`
`647`	`647`	`__possibly_const_range(_Range& __r) noexcept`
`648`	`648`	`{`
	`649`	`+ // _GLIBCXX_RESOLVE_LIB_DEFECTS`
	`650`	`+ // 4027. possibly-const-range should prefer returning const R&`
`649`	`651`	`if constexpr (input_range<const _Range>)`
`650`	`652`	`return const_cast<const _Range&>(__r);`
`651`	`653`	`else`