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
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
