Tested x86_64-linux. Pushed to trunk. -- >8 --
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 @@ <span class="bold"><strong><code class="code">path::lexically_relative</code> is confused by trailing slashes </strong></span> </span></dt><dd><p>Implement the fix for trailing slashes. + </p></dd><dt><a id="manual.bugs.dr3656"></a><span class="term"><a class="link" href="http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#3656" target="_top">3656</a>: + <span class="bold"><strong>Inconsistent bit operations returning a count + </strong></span> + </span></dt><dd><p>Changed <code class="code">bit_width</code> to return <code class="code">int</code>. </p></dd></dl></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="license.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="status.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="setup.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">License </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 2. Setup</td></tr></table></div></body></html> \ 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. <listitem><para>Implement the fix for trailing slashes. </para></listitem></varlistentry> + <varlistentry xml:id="manual.bugs.dr3656"><term><link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="&DR;#3656">3656</link>: + <emphasis role="bold">Inconsistent bit operations returning a count + </emphasis> + </term> + <listitem><para>Changed <code>bit_width</code> to return <code>int</code>. + </para></listitem></varlistentry> + </variablelist> </section> 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<typename _Tp> - 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<typename _Tp> - 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 <bit> + +template<typename T> constexpr bool is_int = false; +template<> constexpr bool is_int<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<decltype(std::bit_width(1u))> ); +static_assert( is_int<decltype(std::bit_width(1ul))> ); +static_assert( is_int<decltype(std::bit_width(1ull))> ); +static_assert( is_int<decltype(std::bit_width((unsigned short)1))> ); +static_assert( is_int<decltype(std::bit_width((unsigned char)1))> ); -- 2.38.1