libstdc++-v3/testsuite/26_numerics/bit/bit.count/countr_zero.cc

   1 // Copyright (C) 2018-2024 Free Software Foundation, Inc.
   2 //
   3 // This file is part of the GNU ISO C++ Library.  This library is free
   4 // software; you can redistribute it and/or modify it under the
   5 // terms of the GNU General Public License as published by the
   6 // Free Software Foundation; either version 3, or (at your option)
   7 // any later version.
   8
   9 // This library is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13
  14 // You should have received a copy of the GNU General Public License along
  15 // with this library; see the file COPYING3.  If not see
  16 // <http://www.gnu.org/licenses/>.
  17
  18 // { dg-do compile { target c++20 } }
  19
  20 #include <bit>
  21 #include <limits>
  22
  23 template<typename UInt>
  24 constexpr auto
  25 test(UInt x)
  26 -> decltype(std::countr_zero(x))
  27 {
  28   static_assert( noexcept(std::countr_zero(x)) );
  29
  30   constexpr unsigned digits = std::numeric_limits<UInt>::digits;
  31
  32   static_assert( std::countr_zero((UInt)0) == digits );
  33   static_assert( std::countr_zero((UInt)-1) == 0 );
  34   static_assert( std::countr_zero((UInt)127) == 0 );
  35
  36   static_assert( std::countr_zero((UInt)1) == 0 );
  37   static_assert( std::countr_zero((UInt)2) == 1 );
  38   static_assert( std::countr_zero((UInt)0x70) == 4 );
  39
  40   if constexpr (std::numeric_limits<UInt>::digits > 8)
  41   {
  42     static_assert( std::countr_zero((UInt)(1u << 8)) == 8 );
  43     static_assert( std::countr_zero((UInt)(4u << 9)) == 11 );
  44   }
  45
  46   if constexpr (std::numeric_limits<UInt>::digits > 64)
  47   {
  48     static_assert( std::countr_zero((UInt)2 << 70) == 71 );
  49   }
  50
  51   return true;
  52 }
  53
  54 static_assert( test( (unsigned char)0 ) );
  55 static_assert( test( (unsigned short)0 ) );
  56 static_assert( test( (unsigned int)0 ) );
  57 static_assert( test( (unsigned long)0 ) );
  58 static_assert( test( (unsigned long long)0 ) );
  59
  60 // std::countr_zero(T) shall not participate in overload resolution
  61 // unless T is an unsigned integer type.
  62 struct X { constexpr bool did_not_match() { return true; } };
  63 constexpr X test(...) { return X{}; }
  64 static_assert( test( (bool)0 ).did_not_match() );
  65 static_assert( test( (char)0 ).did_not_match() );
  66 static_assert( test( (int)0 ).did_not_match() );
  67 static_assert( test( (char16_t)0 ).did_not_match() );
  68 static_assert( test( (float)0 ).did_not_match() );
  69 static_assert( test( (void*)0 ).did_not_match() );
  70 static_assert( test( X{} ).did_not_match() );
  71 enum E : unsigned { e };
  72 static_assert( test( e ).did_not_match() );
  73
  74 #if !defined(__STRICT_ANSI__) && defined __SIZEOF_INT128__
  75 static_assert( test( (unsigned __int128)0 ) );
  76 static_assert( test( (__int128)0 ).did_not_match() );
  77 #endif
  78 #if defined(__GLIBCXX_TYPE_INT_N_0)
  79 static_assert( test( (unsigned __GLIBCXX_TYPE_INT_N_0)0 ) );
  80 static_assert( test( (__GLIBCXX_TYPE_INT_N_0)0 ).did_not_match() );
  81 #endif
  82 #if defined(__GLIBCXX_TYPE_INT_N_1)
  83 static_assert( test( (unsigned __GLIBCXX_TYPE_INT_N_1)0 ) );
  84 static_assert( test( (__GLIBCXX_TYPE_INT_N_1)0 ).did_not_match() );
  85 #endif
  86 #if defined(__GLIBCXX_TYPE_INT_N_2)
  87 static_assert( test( (unsigned __GLIBCXX_TYPE_INT_N_2)0 ) );
  88 static_assert( test( (__GLIBCXX_TYPE_INT_N_2)0 ).did_not_match() );
  89 #endif
  90 #if defined(__GLIBCXX_TYPE_INT_N_3)
  91 static_assert( test( (unsigned __GLIBCXX_TYPE_INT_N_3)0 ) );
  92 static_assert( test( (__GLIBCXX_TYPE_INT_N_3)0 ).did_not_match() );
  93 #endif
  94
  95 #include <cstddef>
  96 static_assert( test( (std::byte)0 ).did_not_match() );