I'm testing this patch for gcc-13 as a better fix for PR109921, without
the breakage that r14-1431-g7037e7b6e4ac41 caused on trunk.
If testing goes well I'll push this before the 13.2 release candidate.
-- >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 _Float128 overload in terms of a
non-existing from_chars_strtod function.
Only try to use __strtof128 if uselocale is available and therefore we
can use the from_chars_strtod function template.
This is a simpler change than r14-1431-g7037e7b6e4ac41 on trunk, because
that caused unwanted ABI regressions (PR libstdc++/110077).
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.
---
libstdc++-v3/src/c++17/floating_from_chars.cc | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/libstdc++-v3/src/c++17/floating_from_chars.cc
b/libstdc++-v3/src/c++17/floating_from_chars.cc
index 78b9d92cdc0..b3061bdca01 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
@@ -1211,7 +1207,7 @@ 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).
@@ -1280,6 +1276,7 @@ _ZSt10from_charsPKcS0_RDF128_St12chars_format(const char*
first,
chars_format fmt) noexcept
__attribute__((alias ("_ZSt10from_charsPKcS0_Ru9__ieee128St12chars_format")));
#elif defined(USE_STRTOF128_FOR_FROM_CHARS)
+// Overload for _Float128 is not defined inline in <charconv>, define it here.
from_chars_result
from_chars(const char* first, const char* last, _Float128& value,
chars_format fmt) noexcept
--
2.41.0
