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libstdc++: Replace std::isdigit and std::isxdigit in <format> [PR107817]

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These functions aren't usable in constant expressions. Provide our own
implementations, based on __from_chars_alnum_to_val from <charconv>.

libstdc++-v3/ChangeLog:

	PR libstdc++/107817
	* include/std/charconv (__from_chars_alnum_to_val): Add
	constexpr for C++20.
	* include/std/format (__is_digit, __is_xdigit): New functions.
	(_Spec::_S_parse_width_or_precision): Use __is_digit.
	(__formatter_fp::parse): Use __is_xdigit.
This commit is contained in:
Jonathan Wakely 2022-11-22 17:39:43 +00:00
parent 6b859736bb
commit dfc1ea414e
2 changed files with 10 additions and 4 deletions
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2
libstdc++-v3/include/std/charconv
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@ -454,7 +454,7 @@ namespace __detail
// If _DecOnly is false: if the character is an alphanumeric digit, then
// return its corresponding base-36 value, otherwise return a value >= 127.
template<bool _DecOnly = false>
_GLIBCXX23_CONSTEXPR unsigned char
_GLIBCXX20_CONSTEXPR unsigned char
__from_chars_alnum_to_val(unsigned char __c)
{
if _GLIBCXX17_CONSTEXPR (_DecOnly)

12
libstdc++-v3/include/std/format
View file

@ -358,6 +358,12 @@ namespace __format
size_t
__int_from_arg(const basic_format_arg<_Context>& __arg);
constexpr bool __is_digit(char __c)
{ return std::__detail::__from_chars_alnum_to_val(__c) < 10; }
constexpr bool __is_xdigit(char __c)
{ return std::__detail::__from_chars_alnum_to_val(__c) < 16; }
template<typename _CharT>
struct _Spec
{
@ -469,7 +475,7 @@ namespace __format
unsigned short& __val, bool& __arg_id,
basic_format_parse_context<_CharT>& __pc)
{
if (std::isdigit(*__first))
if (__format::__is_digit(*__first))
{
auto [__v, __ptr] = __format::__parse_integer(__first, __last);
if (!__ptr)
@ -1537,7 +1543,7 @@ namespace __format
if (__trailing_zeros)
{
if (!std::isxdigit(__s[0]))
if (!__format::__is_xdigit(__s[0]))
--__sigfigs;
__z = __prec - __sigfigs;
}
@ -1627,7 +1633,7 @@ namespace __format
{
__fill_char = _CharT('0');
// Write sign before zero filling.
if (!std::isxdigit(__narrow_str[0]))
if (!__format::__is_xdigit(__narrow_str[0]))
{
*__out++ = __str[0];
__str.remove_prefix(1);