[libc++][NFC] Simplify the implementation of numeric_limits

[philnik777]

The cv specializations for numeric_limits inherited privately for some reason. We can simplify the implementation by inheriting publicly and removing the members that just replicate the values from the base class.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Nikolas Klauser (philnik777)

Changes

The cv specializations for numeric_limits inherited privately for some reason. We can simplify the implementation by inheriting publicly and removing the members that just replicate the values from the base cl
ass.

---

Full diff: https://github.com/llvm/llvm-project/pull/80425.diff

1 Files Affected:

• (modified) libcxx/include/limits (+5-278)

diff --git a/libcxx/include/limits b/libcxx/include/limits
index a240580c0132f..c704b4dddaf8e 100644
--- a/libcxx/include/limits
+++ b/libcxx/include/limits
@@ -436,8 +436,8 @@ protected:
 };
 
 template <class _Tp>
-class _LIBCPP_TEMPLATE_VIS numeric_limits : private __libcpp_numeric_limits<__remove_cv_t<_Tp> > {
-  typedef __libcpp_numeric_limits<__remove_cv_t<_Tp> > __base;
+class _LIBCPP_TEMPLATE_VIS numeric_limits : private __libcpp_numeric_limits<_Tp> {
+  typedef __libcpp_numeric_limits<_Tp> __base;
   typedef typename __base::type type;
 
 public:
@@ -530,286 +530,13 @@ template <class _Tp>
 _LIBCPP_CONSTEXPR const float_round_style numeric_limits<_Tp>::round_style;
 
 template <class _Tp>
-class _LIBCPP_TEMPLATE_VIS numeric_limits<const _Tp> : private numeric_limits<_Tp> {
-  typedef numeric_limits<_Tp> __base;
-  typedef _Tp type;
-
-public:
-  static _LIBCPP_CONSTEXPR const bool is_specialized = __base::is_specialized;
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type min() _NOEXCEPT { return __base::min(); }
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type max() _NOEXCEPT { return __base::max(); }
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type lowest() _NOEXCEPT { return __base::lowest(); }
-
-  static _LIBCPP_CONSTEXPR const int digits       = __base::digits;
-  static _LIBCPP_CONSTEXPR const int digits10     = __base::digits10;
-  static _LIBCPP_CONSTEXPR const int max_digits10 = __base::max_digits10;
-  static _LIBCPP_CONSTEXPR const bool is_signed   = __base::is_signed;
-  static _LIBCPP_CONSTEXPR const bool is_integer  = __base::is_integer;
-  static _LIBCPP_CONSTEXPR const bool is_exact    = __base::is_exact;
-  static _LIBCPP_CONSTEXPR const int radix        = __base::radix;
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type epsilon() _NOEXCEPT { return __base::epsilon(); }
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type round_error() _NOEXCEPT { return __base::round_error(); }
+class _LIBCPP_TEMPLATE_VIS numeric_limits<const _Tp> : public numeric_limits<_Tp> {};
 
-  static _LIBCPP_CONSTEXPR const int min_exponent   = __base::min_exponent;
-  static _LIBCPP_CONSTEXPR const int min_exponent10 = __base::min_exponent10;
-  static _LIBCPP_CONSTEXPR const int max_exponent   = __base::max_exponent;
-  static _LIBCPP_CONSTEXPR const int max_exponent10 = __base::max_exponent10;
-
-  static _LIBCPP_CONSTEXPR const bool has_infinity      = __base::has_infinity;
-  static _LIBCPP_CONSTEXPR const bool has_quiet_NaN     = __base::has_quiet_NaN;
-  static _LIBCPP_CONSTEXPR const bool has_signaling_NaN = __base::has_signaling_NaN;
-  _LIBCPP_SUPPRESS_DEPRECATED_PUSH
-  static _LIBCPP_DEPRECATED_IN_CXX23 _LIBCPP_CONSTEXPR const float_denorm_style has_denorm = __base::has_denorm;
-  static _LIBCPP_DEPRECATED_IN_CXX23 _LIBCPP_CONSTEXPR const bool has_denorm_loss          = __base::has_denorm_loss;
-  _LIBCPP_SUPPRESS_DEPRECATED_POP
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type infinity() _NOEXCEPT { return __base::infinity(); }
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type quiet_NaN() _NOEXCEPT { return __base::quiet_NaN(); }
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type signaling_NaN() _NOEXCEPT { return __base::signaling_NaN(); }
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type denorm_min() _NOEXCEPT { return __base::denorm_min(); }
-
-  static _LIBCPP_CONSTEXPR const bool is_iec559  = __base::is_iec559;
-  static _LIBCPP_CONSTEXPR const bool is_bounded = __base::is_bounded;
-  static _LIBCPP_CONSTEXPR const bool is_modulo  = __base::is_modulo;
-
-  static _LIBCPP_CONSTEXPR const bool traps                    = __base::traps;
-  static _LIBCPP_CONSTEXPR const bool tinyness_before          = __base::tinyness_before;
-  static _LIBCPP_CONSTEXPR const float_round_style round_style = __base::round_style;
-};
-
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const _Tp>::is_specialized;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<const _Tp>::digits;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<const _Tp>::digits10;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<const _Tp>::max_digits10;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const _Tp>::is_signed;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const _Tp>::is_integer;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const _Tp>::is_exact;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<const _Tp>::radix;
 template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<const _Tp>::min_exponent;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<const _Tp>::min_exponent10;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<const _Tp>::max_exponent;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<const _Tp>::max_exponent10;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const _Tp>::has_infinity;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const _Tp>::has_quiet_NaN;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const _Tp>::has_signaling_NaN;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const float_denorm_style numeric_limits<const _Tp>::has_denorm;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const _Tp>::has_denorm_loss;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const _Tp>::is_iec559;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const _Tp>::is_bounded;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const _Tp>::is_modulo;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const _Tp>::traps;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const _Tp>::tinyness_before;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const float_round_style numeric_limits<const _Tp>::round_style;
-
-template <class _Tp>
-class _LIBCPP_TEMPLATE_VIS numeric_limits<volatile _Tp> : private numeric_limits<_Tp> {
-  typedef numeric_limits<_Tp> __base;
-  typedef _Tp type;
-
-public:
-  static _LIBCPP_CONSTEXPR const bool is_specialized = __base::is_specialized;
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type min() _NOEXCEPT { return __base::min(); }
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type max() _NOEXCEPT { return __base::max(); }
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type lowest() _NOEXCEPT { return __base::lowest(); }
-
-  static _LIBCPP_CONSTEXPR const int digits       = __base::digits;
-  static _LIBCPP_CONSTEXPR const int digits10     = __base::digits10;
-  static _LIBCPP_CONSTEXPR const int max_digits10 = __base::max_digits10;
-  static _LIBCPP_CONSTEXPR const bool is_signed   = __base::is_signed;
-  static _LIBCPP_CONSTEXPR const bool is_integer  = __base::is_integer;
-  static _LIBCPP_CONSTEXPR const bool is_exact    = __base::is_exact;
-  static _LIBCPP_CONSTEXPR const int radix        = __base::radix;
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type epsilon() _NOEXCEPT { return __base::epsilon(); }
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type round_error() _NOEXCEPT { return __base::round_error(); }
-
-  static _LIBCPP_CONSTEXPR const int min_exponent   = __base::min_exponent;
-  static _LIBCPP_CONSTEXPR const int min_exponent10 = __base::min_exponent10;
-  static _LIBCPP_CONSTEXPR const int max_exponent   = __base::max_exponent;
-  static _LIBCPP_CONSTEXPR const int max_exponent10 = __base::max_exponent10;
-
-  static _LIBCPP_CONSTEXPR const bool has_infinity      = __base::has_infinity;
-  static _LIBCPP_CONSTEXPR const bool has_quiet_NaN     = __base::has_quiet_NaN;
-  static _LIBCPP_CONSTEXPR const bool has_signaling_NaN = __base::has_signaling_NaN;
-  _LIBCPP_SUPPRESS_DEPRECATED_PUSH
-  static _LIBCPP_DEPRECATED_IN_CXX23 _LIBCPP_CONSTEXPR const float_denorm_style has_denorm = __base::has_denorm;
-  static _LIBCPP_DEPRECATED_IN_CXX23 _LIBCPP_CONSTEXPR const bool has_denorm_loss          = __base::has_denorm_loss;
-  _LIBCPP_SUPPRESS_DEPRECATED_POP
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type infinity() _NOEXCEPT { return __base::infinity(); }
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type quiet_NaN() _NOEXCEPT { return __base::quiet_NaN(); }
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type signaling_NaN() _NOEXCEPT { return __base::signaling_NaN(); }
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type denorm_min() _NOEXCEPT { return __base::denorm_min(); }
+class _LIBCPP_TEMPLATE_VIS numeric_limits<volatile _Tp> : public numeric_limits<_Tp> {};
 
-  static _LIBCPP_CONSTEXPR const bool is_iec559  = __base::is_iec559;
-  static _LIBCPP_CONSTEXPR const bool is_bounded = __base::is_bounded;
-  static _LIBCPP_CONSTEXPR const bool is_modulo  = __base::is_modulo;
-
-  static _LIBCPP_CONSTEXPR const bool traps                    = __base::traps;
-  static _LIBCPP_CONSTEXPR const bool tinyness_before          = __base::tinyness_before;
-  static _LIBCPP_CONSTEXPR const float_round_style round_style = __base::round_style;
-};
-
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<volatile _Tp>::is_specialized;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<volatile _Tp>::digits;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<volatile _Tp>::digits10;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<volatile _Tp>::max_digits10;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<volatile _Tp>::is_signed;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<volatile _Tp>::is_integer;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<volatile _Tp>::is_exact;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<volatile _Tp>::radix;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<volatile _Tp>::min_exponent;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<volatile _Tp>::min_exponent10;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<volatile _Tp>::max_exponent;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<volatile _Tp>::max_exponent10;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<volatile _Tp>::has_infinity;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<volatile _Tp>::has_quiet_NaN;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<volatile _Tp>::has_signaling_NaN;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const float_denorm_style numeric_limits<volatile _Tp>::has_denorm;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<volatile _Tp>::has_denorm_loss;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<volatile _Tp>::is_iec559;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<volatile _Tp>::is_bounded;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<volatile _Tp>::is_modulo;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<volatile _Tp>::traps;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<volatile _Tp>::tinyness_before;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const float_round_style numeric_limits<volatile _Tp>::round_style;
-
-template <class _Tp>
-class _LIBCPP_TEMPLATE_VIS numeric_limits<const volatile _Tp> : private numeric_limits<_Tp> {
-  typedef numeric_limits<_Tp> __base;
-  typedef _Tp type;
-
-public:
-  static _LIBCPP_CONSTEXPR const bool is_specialized = __base::is_specialized;
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type min() _NOEXCEPT { return __base::min(); }
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type max() _NOEXCEPT { return __base::max(); }
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type lowest() _NOEXCEPT { return __base::lowest(); }
-
-  static _LIBCPP_CONSTEXPR const int digits       = __base::digits;
-  static _LIBCPP_CONSTEXPR const int digits10     = __base::digits10;
-  static _LIBCPP_CONSTEXPR const int max_digits10 = __base::max_digits10;
-  static _LIBCPP_CONSTEXPR const bool is_signed   = __base::is_signed;
-  static _LIBCPP_CONSTEXPR const bool is_integer  = __base::is_integer;
-  static _LIBCPP_CONSTEXPR const bool is_exact    = __base::is_exact;
-  static _LIBCPP_CONSTEXPR const int radix        = __base::radix;
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type epsilon() _NOEXCEPT { return __base::epsilon(); }
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type round_error() _NOEXCEPT { return __base::round_error(); }
-
-  static _LIBCPP_CONSTEXPR const int min_exponent   = __base::min_exponent;
-  static _LIBCPP_CONSTEXPR const int min_exponent10 = __base::min_exponent10;
-  static _LIBCPP_CONSTEXPR const int max_exponent   = __base::max_exponent;
-  static _LIBCPP_CONSTEXPR const int max_exponent10 = __base::max_exponent10;
-
-  static _LIBCPP_CONSTEXPR const bool has_infinity      = __base::has_infinity;
-  static _LIBCPP_CONSTEXPR const bool has_quiet_NaN     = __base::has_quiet_NaN;
-  static _LIBCPP_CONSTEXPR const bool has_signaling_NaN = __base::has_signaling_NaN;
-  _LIBCPP_SUPPRESS_DEPRECATED_PUSH
-  static _LIBCPP_DEPRECATED_IN_CXX23 _LIBCPP_CONSTEXPR const float_denorm_style has_denorm = __base::has_denorm;
-  static _LIBCPP_DEPRECATED_IN_CXX23 _LIBCPP_CONSTEXPR const bool has_denorm_loss          = __base::has_denorm_loss;
-  _LIBCPP_SUPPRESS_DEPRECATED_POP
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type infinity() _NOEXCEPT { return __base::infinity(); }
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type quiet_NaN() _NOEXCEPT { return __base::quiet_NaN(); }
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type signaling_NaN() _NOEXCEPT { return __base::signaling_NaN(); }
-  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR type denorm_min() _NOEXCEPT { return __base::denorm_min(); }
-
-  static _LIBCPP_CONSTEXPR const bool is_iec559  = __base::is_iec559;
-  static _LIBCPP_CONSTEXPR const bool is_bounded = __base::is_bounded;
-  static _LIBCPP_CONSTEXPR const bool is_modulo  = __base::is_modulo;
-
-  static _LIBCPP_CONSTEXPR const bool traps                    = __base::traps;
-  static _LIBCPP_CONSTEXPR const bool tinyness_before          = __base::tinyness_before;
-  static _LIBCPP_CONSTEXPR const float_round_style round_style = __base::round_style;
-};
-
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const volatile _Tp>::is_specialized;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<const volatile _Tp>::digits;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<const volatile _Tp>::digits10;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<const volatile _Tp>::max_digits10;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const volatile _Tp>::is_signed;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const volatile _Tp>::is_integer;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const volatile _Tp>::is_exact;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<const volatile _Tp>::radix;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<const volatile _Tp>::min_exponent;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<const volatile _Tp>::min_exponent10;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<const volatile _Tp>::max_exponent;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const int numeric_limits<const volatile _Tp>::max_exponent10;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const volatile _Tp>::has_infinity;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const volatile _Tp>::has_quiet_NaN;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const volatile _Tp>::has_signaling_NaN;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const float_denorm_style numeric_limits<const volatile _Tp>::has_denorm;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const volatile _Tp>::has_denorm_loss;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const volatile _Tp>::is_iec559;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const volatile _Tp>::is_bounded;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const volatile _Tp>::is_modulo;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const volatile _Tp>::traps;
-template <class _Tp>
-_LIBCPP_CONSTEXPR const bool numeric_limits<const volatile _Tp>::tinyness_before;
 template <class _Tp>
-_LIBCPP_CONSTEXPR const float_round_style numeric_limits<const volatile _Tp>::round_style;
+class _LIBCPP_TEMPLATE_VIS numeric_limits<const volatile _Tp> : public numeric_limits<_Tp> {};
 
 _LIBCPP_END_NAMESPACE_STD
 

[ldionne]

After discussion, we can't think of a case that this refactoring breaks. Regarding the fly-by removal of __remove_cv_t, it was previously impossible to call __libcpp_numeric_limits with a cv-qualified type anyway, cause they were stripped by the top-level numeric_limits templates.

So I think this is fine, however let's monitor this patch in case someone complains, since it's possible the code was written this way for a reason back in the days, and we just can't figure it out right now.

[ldionne]

Do we have tests for numeric limits with cv-qualified types? If not, we need to add some before we merge this.