libstdc++: Provide formatter for vector<bool>::reference [PR109162]

This patch implement formatter for vector<bool>::reference which
is part of P2286R8.

To indicate partial support we define __glibcxx_format_ranges macro
value 1, without defining __cpp_lib_format_ranges.

To avoid including the whole content of the <format> header, we
introduce new bits/formatfwd.h forward declares classes required
for newly introduce formatter.

The signatures of the user-facing parse and format method of the provided
formatters deviate from the standard by constraining types of params:
* _Bit_reference instead T satisfying is-vector-bool-reference<T>
* _CharT is constrained __formatter::__char
* basic_format_parse_context<_CharT> for parse argument
* basic_format_context<_Out, _CharT> for format second argument
The standard specifies last three of above as unconstrained types, which leads
to formattable<vector<bool>::reference, char32_t> (and any other type as char)
being true.

	PR libstdc++/109162

libstdc++-v3/ChangeLog:

	* include/Makefile.am: Add bits/formatfwd.h.
	* include/Makefile.in: Add bits/formatfwd.h.
	* include/bits/version.def: Define __glibcxx_format_ranges without
	corresponding std name.
	* include/bits/version.h: Regenerate.
	* include/std/format (basic_format_context, __format::__char):
	Move declartions to bits/formatfwd.h.
	(formatter<_Tp, _CharT>): Remove default argument for _CharT
	parameter, now specified in forward declaration in bits/formatfwd.h.
	* include/std/vector (formatter<_Bit_reference, _CharT>): Define.
	* include/bits/formatfwd.h: New file with forward declarations
	for bits of std/format.
	* testsuite/23_containers/vector/bool/format.cc: New test.

Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>

0 files changed, 0 insertions, 0 deletions