Floating points types _Float16, _Float32, _Float64, and bfloat16,
can be formatted only if std::to_chars overloads for such types
where 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.
---
Tested on x86_64-linux. OK for trunk?
libstdc++-v3/include/std/format | 32 ++++++++------------------------
1 file changed, 8 insertions(+), 24 deletions(-)
diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format
index e7e0d2d142b..1809f040077 100644
--- a/libstdc++-v3/include/std/format
+++ b/libstdc++-v3/include/std/format
@@ -2276,7 +2276,7 @@ namespace __format
};
#endif
-#ifdef __STDCPP_FLOAT16_T__
+#if defined(__STDCPP_FLOAT16_T__) && defined(_GLIBCXX_FLOAT_IS_IEEE_BINARY32)
// Reuse __formatter_fp<C>::format<float, Out> for _Float16.
template<__format::__char _CharT>
struct formatter<_Float16, _CharT>
@@ -2298,7 +2298,7 @@ namespace __format
};
#endif
-#if defined(__FLT32_DIG__)
+#if defined(__FLT32_DIG__) && defined(_GLIBCXX_FLOAT_IS_IEEE_BINARY32)
// Reuse __formatter_fp<C>::format<float, Out> for _Float32.
template<__format::__char _CharT>
struct formatter<_Float32, _CharT>
@@ -2320,7 +2320,7 @@ namespace __format
};
#endif
-#if defined(__FLT64_DIG__)
+#if defined(__FLT64_DIG__) && defined(_GLIBCXX_DOUBLE_IS_IEEE_BINARY64)
// Reuse __formatter_fp<C>::format<double, Out> for _Float64.
template<__format::__char _CharT>
struct formatter<_Float64, _CharT>
@@ -2364,7 +2364,7 @@ namespace __format
};
#endif
-#ifdef __STDCPP_BFLOAT16_T__
+#if defined(__STDCPP_BFLOAT16_T__) && defined(_GLIBCXX_FLOAT_IS_IEEE_BINARY32)
// Reuse __formatter_fp<C>::format<float, Out> for bfloat16_t.
template<__format::__char _CharT>
struct formatter<__gnu_cxx::__bfloat16_t, _CharT>
@@ -3443,22 +3443,16 @@ namespace __format
return type_identity<float>();
#endif
-#ifdef __FLT32_DIG__
+#if defined(__FLT32_DIG__) && defined(_GLIBCXX_FLOAT_IS_IEEE_BINARY32)
else if constexpr (is_same_v<_Td, _Float32>)
-# ifdef _GLIBCXX_FLOAT_IS_IEEE_BINARY32
return type_identity<float>();
-# else
- return type_identity<_Float32>();
-# endif
#endif
-#ifdef __FLT64_DIG__
+
+#if defined(__FLT64_DIG__) && defined(_GLIBCXX_DOUBLE_IS_IEEE_BINARY64)
else if constexpr (is_same_v<_Td, _Float64>)
-# ifdef _GLIBCXX_DOUBLE_IS_IEEE_BINARY64
return type_identity<double>();
-# else
- return type_identity<_Float64>();
-# endif
#endif
+
#if _GLIBCXX_FORMAT_F128
# if __FLT128_DIG__
else if constexpr (is_same_v<_Td, _Float128>)
@@ -3538,16 +3532,6 @@ namespace __format
return _Arg_u128;
#endif
- // N.B. some of these types will never actually be used here,
- // because they get normalized to a standard floating-point type.
-#if defined __FLT32_DIG__ && ! _GLIBCXX_FLOAT_IS_IEEE_BINARY32
- else if constexpr (is_same_v<_Tp, _Float32>)
- return _Arg_f32;
-#endif
-#if defined __FLT64_DIG__ && ! _GLIBCXX_DOUBLE_IS_IEEE_BINARY64
- else if constexpr (is_same_v<_Tp, _Float64>)
- return _Arg_f64;
-#endif
#if _GLIBCXX_FORMAT_F128 == 2
else if constexpr (is_same_v<_Tp, __format::__float128_t>)
return _Arg_f128;
--
2.48.1
