libstdc++: Correct preprocessing checks for floatX_t and bfloat_16 formatting

Floating points types _Float16, _Float32, _Float64, and bfloat16,
can be formatted only if std::to_chars overloads for such types
were provided. Currently this is only the case for architectures
where float and double are 32-bits and 64-bits IEEE floating points types.

This patch updates the preprocessing checks for formatters
for above types to check _GLIBCXX_FLOAT_IS_IEEE_BINARY32
and _GLIBCXX_DOUBLE_IS_IEEE_BINARY64. Making them non-formattable
on non-IEEE architectures.

Remove a potential UB, where we could produce basic_format_arg
with _M_type set to _Arg_fp32 or _Arg_fp64, that was later not
handled by `_M_visit`.

libstdc++-v3/ChangeLog:

	* include/std/format (formatter<_Float16, _CharT>): Define only if
	_GLIBCXX_FLOAT_IS_IEEE_BINARY32 macro is defined.
	(formatter<_Float16, _CharT>): As above.
	(formatter<__gnu_cxx::__bfloat16_t, _CharT>): As above.
	(formatter<_Float64, _CharT>): Define only if
	_GLIBCXX_DOUBLE_IS_IEEE_BINARY64 is defined.
	(basic_format_arg::_S_to_arg_type): Normalize _Float32 and _Float64
	only to float and double respectivelly.
	(basic_format_arg::_S_to_enum): Remove handling of _Float32 and _Float64.

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

0 files changed, 0 insertions, 0 deletions