libstdc++-v3/testsuite/26_numerics/bit/bit.cast/bit_cast.cc

   1 // Copyright (C) 2020-2024 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 // { dg-add-options no_pch }
  20
  21 #include <bit>
  22
  23 #ifndef __cpp_lib_bit_cast
  24 # error "Feature-test macro for bit_cast missing in <bit>"
  25 #elif __cpp_lib_bit_cast != 201806L
  26 # error "Feature-test macro for bit_cast has wrong value in <bit>"
  27 #endif
  28
  29 #include <cstdint>
  30 #include <cstring>
  31 #include <testsuite_hooks.h>
  32
  33 template<typename To, typename From>
  34 constexpr bool
  35 check(const From& from)
  36 {
  37   return std::bit_cast<From>(std::bit_cast<To>(from)) == from;
  38 }
  39
  40 void
  41 test01()
  42 {
  43   static_assert( std::bit_cast<int>(123) == 123 );
  44   static_assert( std::bit_cast<int>(123u) == 123 );
  45   static_assert( std::bit_cast<int>(~0u) == ~0 );
  46
  47   if constexpr (sizeof(int) == sizeof(float))
  48     static_assert( check<int>(12.34f) );
  49   if constexpr (sizeof(unsigned long long) == sizeof(double))
  50     static_assert( check<unsigned long long>(123.456) );
  51   if constexpr (sizeof(std::intptr_t) == sizeof(void(*)()))
  52     VERIFY( check<std::intptr_t>(&test01) );
  53 }
  54
  55 void
  56 test02()
  57 {
  58   struct S
  59   {
  60     int i;
  61
  62     bool operator==(const char* s) const
  63     { return std::memcmp(&i, s, sizeof(i)) == 0; }
  64   };
  65
  66   char arr[sizeof(int)];
  67   char arr2[sizeof(int)];
  68   for (int i = 0; i < sizeof(int); ++i)
  69   {
  70     arr[i] = i + 1;
  71     arr2[i] = (i + 1) * -(i % 2);
  72   }
  73   VERIFY( std::bit_cast<S>(arr) == arr );
  74   VERIFY( std::bit_cast<S>(arr2) == arr2 );
  75 }
  76
  77 int main()
  78 {
  79   test01();
  80   test02();
  81 }