Tested powerpc64le-linux. Pushed to trunk.
-- >8 --
We use the from_chars_strtod function with __strtof128 to read a
_Float128 value, but from_chars_strtod is not defined unless uselocale
is available. This can lead to compilation failures for some targets,
because we try to define the _Flaot128 overload in terms of a
non-existing from_chars_strtod function.
Only try to use __strtof128 if uselocale is available, otherwise
fallback to the long double overload of std::from_chars (which might
fallback to the double overload, which should use fast_float).
This ensures we always define the full set of overloads, even if they
are not always accurate for all values of the wider types.
libstdc++-v3/ChangeLog:
PR libstdc++/109921
* src/c++17/floating_from_chars.cc (USE_STRTOF128_FOR_FROM_CHARS):
Only define when USE_STRTOD_FOR_FROM_CHARS is also defined.
(USE_STRTOD_FOR_FROM_CHARS): Do not undefine when long double is
binary64.
(from_chars(const char*, const char*, double&, chars_format)):
Check __LDBL_MANT_DIG__ == __DBL_MANT_DIG__ here.
(from_chars(const char*, const char*, _Float128&, chars_format))
Only use from_chars_strtod when USE_STRTOD_FOR_FROM_CHARS is
defined, otherwise parse a long double and convert to _Float128.
---
libstdc++-v3/src/c++17/floating_from_chars.cc | 20 ++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)
diff --git a/libstdc++-v3/src/c++17/floating_from_chars.cc
b/libstdc++-v3/src/c++17/floating_from_chars.cc
index ebd428d5be3..eea878072b0 100644
--- a/libstdc++-v3/src/c++17/floating_from_chars.cc
+++ b/libstdc++-v3/src/c++17/floating_from_chars.cc
@@ -64,7 +64,7 @@
// strtold for __ieee128
extern "C" __ieee128 __strtoieee128(const char*, char**);
#elif __FLT128_MANT_DIG__ == 113 && __LDBL_MANT_DIG__ != 113 \
- && defined(__GLIBC_PREREQ)
+ && defined(__GLIBC_PREREQ) && defined(USE_STRTOD_FOR_FROM_CHARS)
#define USE_STRTOF128_FOR_FROM_CHARS 1
extern "C" _Float128 __strtof128(const char*, char**)
__asm ("strtof128")
@@ -77,10 +77,6 @@ extern "C" _Float128 __strtof128(const char*, char**)
#if _GLIBCXX_FLOAT_IS_IEEE_BINARY32 && _GLIBCXX_DOUBLE_IS_IEEE_BINARY64 \
&& __SIZE_WIDTH__ >= 32
# define USE_LIB_FAST_FLOAT 1
-# if __LDBL_MANT_DIG__ == __DBL_MANT_DIG__
-// No need to use strtold.
-# undef USE_STRTOD_FOR_FROM_CHARS
-# endif
#endif
#if USE_LIB_FAST_FLOAT
@@ -1261,7 +1257,7 @@ from_chars_result
from_chars(const char* first, const char* last, long double& value,
chars_format fmt) noexcept
{
-#if ! USE_STRTOD_FOR_FROM_CHARS
+#if __LDBL_MANT_DIG__ == __DBL_MANT_DIG__ || !defined USE_STRTOD_FOR_FROM_CHARS
// Either long double is the same as double, or we can't use strtold.
// In the latter case, this might give an incorrect result (e.g. values
// out of range of double give an error, even if they fit in long double).
@@ -1329,13 +1325,23 @@ _ZSt10from_charsPKcS0_RDF128_St12chars_format(const
char* first,
__ieee128& value,
chars_format fmt) noexcept
__attribute__((alias ("_ZSt10from_charsPKcS0_Ru9__ieee128St12chars_format")));
-#elif defined(USE_STRTOF128_FOR_FROM_CHARS)
+#else
from_chars_result
from_chars(const char* first, const char* last, _Float128& value,
chars_format fmt) noexcept
{
+#ifdef USE_STRTOF128_FOR_FROM_CHARS
// fast_float doesn't support IEEE binary128 format, but we can use strtold.
return from_chars_strtod(first, last, value, fmt);
+#else
+ // Read a long double. This might give an incorrect result (e.g. values
+ // out of range of long double give an error, even if they fit in _Float128).
+ long double ldbl_val;
+ auto res = std::from_chars(first, last, ldbl_val, fmt);
+ if (res.ec == errc{})
+ value = ldbl_val;
+ return res;
+#endif
}
#endif
--
2.40.1
