From 4581328022615c2cb732cfb404151c4b059d26e3 Mon Sep 17 00:00:00 2001 From: Jonathan Wakely Date: Thu, 24 Nov 2022 21:36:07 +0000 Subject: [PATCH] libstdc++: Change return type of std::bit_width to int (LWG 3656) libstdc++-v3/ChangeLog: * doc/html/manual/bugs.html: Regenerate. * doc/xml/manual/intro.xml: Document LWG 3656 change. * include/std/bit (__bit_width, bit_width): Return int. * testsuite/26_numerics/bit/bit.pow.two/lwg3656.cc: New test. --- libstdc++-v3/doc/html/manual/bugs.html | 4 ++++ libstdc++-v3/doc/xml/manual/intro.xml | 7 +++++++ libstdc++-v3/include/std/bit | 6 ++++-- .../26_numerics/bit/bit.pow.two/lwg3656.cc | 15 +++++++++++++++ 4 files changed, 30 insertions(+), 2 deletions(-) create mode 100644 libstdc++-v3/testsuite/26_numerics/bit/bit.pow.two/lwg3656.cc diff --git a/libstdc++-v3/doc/html/manual/bugs.html b/libstdc++-v3/doc/html/manual/bugs.html index 58600cd6ede..c4a2c26ea39 100644 --- a/libstdc++-v3/doc/html/manual/bugs.html +++ b/libstdc++-v3/doc/html/manual/bugs.html @@ -619,4 +619,8 @@ path::lexically_relative is confused by trailing slashes

Implement the fix for trailing slashes. +

3656: + Inconsistent bit operations returning a count + +

Changed bit_width to return int.

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\ No newline at end of file diff --git a/libstdc++-v3/doc/xml/manual/intro.xml b/libstdc++-v3/doc/xml/manual/intro.xml index dee01c82159..aee96e37c61 100644 --- a/libstdc++-v3/doc/xml/manual/intro.xml +++ b/libstdc++-v3/doc/xml/manual/intro.xml @@ -1308,6 +1308,13 @@ requirements of the license of GCC. Implement the fix for trailing slashes. + 3656: + Inconsistent bit operations returning a count + + + Changed bit_width to return int. + + diff --git a/libstdc++-v3/include/std/bit b/libstdc++-v3/include/std/bit index 2fd80187210..3e072ef2113 100644 --- a/libstdc++-v3/include/std/bit +++ b/libstdc++-v3/include/std/bit @@ -361,7 +361,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION } template - constexpr _Tp + constexpr int __bit_width(_Tp __x) noexcept { constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits; @@ -448,9 +448,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION bit_floor(_Tp __x) noexcept { return std::__bit_floor(__x); } + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 3656. Inconsistent bit operations returning a count /// The smallest integer greater than the base-2 logarithm of `x`. template - constexpr _If_is_unsigned_integer<_Tp> + constexpr _If_is_unsigned_integer<_Tp, int> bit_width(_Tp __x) noexcept { return std::__bit_width(__x); } diff --git a/libstdc++-v3/testsuite/26_numerics/bit/bit.pow.two/lwg3656.cc b/libstdc++-v3/testsuite/26_numerics/bit/bit.pow.two/lwg3656.cc new file mode 100644 index 00000000000..4752c3b1d33 --- /dev/null +++ b/libstdc++-v3/testsuite/26_numerics/bit/bit.pow.two/lwg3656.cc @@ -0,0 +1,15 @@ +// { dg-options "-std=gnu++20" } +// { dg-do compile { target c++20 } } + +#include + +template constexpr bool is_int = false; +template<> constexpr bool is_int = true; + +// LWG 3656. Inconsistent bit operations returning a count +// Rturn type of std::bit_width(T) changed from T to int. +static_assert( is_int ); +static_assert( is_int ); +static_assert( is_int ); +static_assert( is_int ); +static_assert( is_int );