On 02/07/25 03:36 +0300, Mateusz Zych wrote:
Hello libstdc++ Team!

I have recently found a bug in libstdc++, that is,
the std::numeric_limits<> template specializations for integer-class types
are missing some of static data members,
which results in compilation errors of valid C++ code:

  - Compiler Explorer: https://godbolt.org/z/E7z4WYfj4

Since adding missing member constants, which are the most relevant to
integer-like types,
was not a lot of code, I have prepared a Git patch with relevant changes.

I hope this patch is useful, Mateusz Zych

Thanks, I don't think there was any reason to omit these members, and I
agree we should add them.

The patch is simple and obvious enough that I don't think we need a
copyright assignment or DCO sign-off, so I'll push this to the
relevant branches. Thanks!


From 1e83287bbd6adf6ad8f483bd2f891692e0bed0c7 Mon Sep 17 00:00:00 2001
From: Mateusz Zych <mte.z...@gmail.com>
Date: Wed, 2 Jul 2025 01:51:40 +0300
Subject: [PATCH] libstdc++: Added missing member constants to numeric_limits
specializations for integer-class types.

25.3.4.4 Concept weakly_incrementable      [iterator.concept.winc]

 (5) For every integer-class type I,
     let B(I) be a unique hypothetical extended integer type
     of the same signedness with the same width as I.

     [Note 2: The corresponding
              hypothetical specialization numeric_limits<B(I)>
              meets the requirements on
              numeric_limits specializations for integral types.]

(11) For every (possibly cv-qualified) integer-class type I,
     numeric_limits<I> is specialized such that:

     - each static data member m
       has the same value as numeric_limits<B(I)>::m, and

     - each static member function f
       returns I(numeric_limits<B(I)>::f()).

libstdc++-v3/ChangeLog:

        * include/bits/max_size_type.h
        (numeric_limits<__max_size_type>): New static data members.
        (numeric_limits<__max_diff_type>): Likewise.
---
libstdc++-v3/include/bits/max_size_type.h | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/libstdc++-v3/include/bits/max_size_type.h 
b/libstdc++-v3/include/bits/max_size_type.h
index 73a6d141d5b..bc7700506a2 100644
--- a/libstdc++-v3/include/bits/max_size_type.h
+++ b/libstdc++-v3/include/bits/max_size_type.h
@@ -775,6 +775,9 @@ namespace ranges
      static constexpr bool is_signed = false;
      static constexpr bool is_integer = true;
      static constexpr bool is_exact = true;
+      static constexpr bool is_bounded = true;
+      static constexpr bool is_modulo = true;
+      static constexpr bool radix = 2;
      static constexpr int digits
        = __gnu_cxx::__int_traits<_Sp::__rep>::__digits + 1;
      static constexpr int digits10
@@ -802,6 +805,9 @@ namespace ranges
      static constexpr bool is_signed = true;
      static constexpr bool is_integer = true;
      static constexpr bool is_exact = true;
+      static constexpr bool is_bounded = true;
+      static constexpr bool is_modulo = false;
+      static constexpr bool radix = 2;
      static constexpr int digits = numeric_limits<_Sp>::digits - 1;
      static constexpr int digits10
        = static_cast<int>(digits * numbers::ln2 / numbers::ln10);
--
2.48.1


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