[committed] libstdc++: Disable std::format of _Float128 if std::to_chars is innaccurate
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Commit Message
Tested x86_64-linux. Pushed to trunk.
-- >8 --
This restricts std::format support for _Float128 (and __float128) to
targets where glibc provides __strfromf128 and so can give correct
output.
libstdc++-v3/ChangeLog:
* include/std/format [__FLT128_DIG__] (_GLIBCXX_FORMAT_F128):
Only support formatting _Float128 when glibc provides the
functionality needed for accurate std::to_chars.
---
libstdc++-v3/include/std/format | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
@@ -1235,13 +1235,13 @@ namespace __format
using __float128_t = long double;
# define _GLIBCXX_FORMAT_F128 1
-#elif __FLT128_DIG__ && defined(__GLIBC_PREREQ) // see floating_to_chars.cc
+#elif __FLT128_DIG__ && defined(_GLIBCXX_HAVE_FLOAT128_MATH)
// Format 128-bit floating-point types using _Float128.
using __float128_t = _Float128;
# define _GLIBCXX_FORMAT_F128 2
-# if __cplusplus == 202002L || !defined(_GLIBCXX_HAVE_FLOAT128_MATH)
+# if __cplusplus == 202002L
// These overloads exist in the library, but are not declared for C++20.
// Make them available as std::__format::to_chars.
to_chars_result