libstdc++: Implement debug format for strings and characters formatters [PR109162]

This patch implements part P2286R8 that specified debug (escaped)
format for the strings and characters sequences. This include both
handling of the '?' format specifier and set_debug_format member.

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

We provide two separate escaping routines depending on the literal
encoding for the corresponding character types. If the character
encoding is Unicode, we follow the specification for the standard
(__format::__write_escaped_unicode).
For other encodings, we escape only characters in range [0x00, 0x80),
interpreting them as ASCII values: [0x00, 0x20), 0x7f and  '\t', '\r',
'\n', '\\', '"', '\'' are escaped. We assume every character outside
this range is printable (__format::_write_escaped_ascii).
In particular we do not yet implement special handling of shift
sequences.

For Unicode escaping a new __unicode::__escape_edges table is introduced,
that encodes information if character belongs to General_Category that is
escaped by the standard (Control or Other). This table is generated from
DerivedGeneralCategory.txt provided by Unicode. Only boolean flag is
preserved to reduce the number of entries. The additional rules for escaping
are handled by __format::__should_escape_unicode.

When width or precision is specified, we emit escaped string to the temporary
buffer and format the resulting string according to the format spec.
For characters use a fixed size stack buffer, for which a new _Fixedbuf_sink is
introduced. For strings, we use _Str_sink and to avoid allocations,
we compute the estimated size of (possibly truncated) input, and if it is
larger than width field we print directly.

	PR libstdc++/109162

contrib/ChangeLog:

	* unicode/README: Mentioned DerivedGeneralCategory.txt.
	* unicode/gen_libstdcxx_unicode_data.py: Generation __escape_edges
	table from DerivedGeneralCategory.txt. Update file name in comments.
	* unicode/DerivedGeneralCategory.txt: Copy of file distributed by
	Unicode Consortium.

libstdc++-v3/ChangeLog:

	* include/bits/chrono_io.h (__detail::_Widen): Moved to std/format file.
	* include/bits/unicode-data.h: Regnerate.
	* include/bits/unicode.h (__unicode::_Utf_iterator::_M_units)
	(__unicode::__should_escape_category): Define.
	* include/std/format (_GLIBCXX_WIDEN_, _GLIBCXX_WIDEN):	Copied from
	include/bits/chrono_io.h.
	(__format::_Widen): Moved from include/bits/chrono_io.h.
	(__format::_Term_char, __format::_Escapes, __format::_Separators)
	(__format::__should_escape_ascii, __format::__should_escape_unicode)
	(__format::__write_escape_seq, __format::__write_escaped_char)
	(__format::__write_escaped_acii, __format::__write_escaped_unicode)
	(__format::__write_escaped): Define.
	(__formatter_str::_S_trunc): Extracted truncation of character
	sequences.
	(__formatter_str::format): Handle _Pres_esc.
	(__formatter_int::_M_do_parse) [__glibcxx_format_ranges]: Parse '?'.
	(__formatter_int::_M_format_character_escaped): Define.
	(formatter<_CharT, _CharT>::format, formatter<char, wchar_t>::format):
	Handle _Pres_esc.
	(__formatter_str::set_debug_format, formatter<...>::set_debug_format)
	Guard with __glibcxx_format_ranges.
	(__format::_Fixedbuf_sink): Define.
	* testsuite/23_containers/vector/bool/format.cc: Use __format::_Widen
	and remove unnecessary <chrono> include.
	* testsuite/std/format/debug.cc: New test.
	* testsuite/std/format/debug_nonunicode.cc: New test.
	* testsuite/std/format/parse_ctx.cc (escaped_strings_supported): Define
	to true if __glibcxx_format_ranges is defined.
	* testsuite/std/format/string.cc (escaped_strings_supported): Define to
	true if __glibcxx_format_ranges is defined.

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

0 files changed, 0 insertions, 0 deletions