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libstdc++: Simplify __numeric_traits definition 

This changes the __numeric_traits primary template to assume its
argument is an integer type. For the three floating point types that are
supported by __numeric_traits_floating an explicit specialization of
__numeric_traits chooses the right base class.

This improves the failure mode for using __numeric_traits with an
unsupported type. Previously it would use __numeric_traits_floating as
the base class, and give somewhat obscure errors for trying to access
the static data members. Now it will use __numeric_traits_integer which
has a static_assert to check for supported types.

As a side effect of this change there is no need to instantiate
__conditional_type to decide which base class to use.

libstdc++-v3/ChangeLog:

	* include/ext/numeric_traits.h (__numeric_traits): Change
	primary template to always derive from __numeric_traits_integer.
	(__numeric_traits<float>, __numeric_traits<double>)
	(__numeric_traits<long double>): Add explicit specializations.
This commit is contained in:
Jonathan Wakely 2020-11-12 13:31:02 +00:00
parent 896db49a44
commit d21776ef90
1 changed files with 23 additions and 10 deletions
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33
libstdc++-v3/include/ext/numeric_traits.h
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@ -176,19 +176,32 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Value>
const int __numeric_traits_floating<_Value>::__max_exponent10;
template<typename _Value>
struct __numeric_traits
: public __conditional_type<__is_integer_nonstrict<_Value>::__value,
__numeric_traits_integer<_Value>,
__numeric_traits_floating<_Value> >::__type
{ };
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
#undef __glibcxx_floating
#undef __glibcxx_max_digits10
#undef __glibcxx_digits10
#undef __glibcxx_max_exponent10
template<typename _Value>
struct __numeric_traits
: public __numeric_traits_integer<_Value>
{ };
template<>
struct __numeric_traits<float>
: public __numeric_traits_floating<float>
{ };
template<>
struct __numeric_traits<double>
: public __numeric_traits_floating<double>
{ };
template<>
struct __numeric_traits<long double>
: public __numeric_traits_floating<long double>
{ };
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
#endif