clang/test/SemaCXX/builtin-bit-cast.cpp

   1 // RUN: %clang_cc1 -verify -std=c++2a -fsyntax-only -triple x86_64-apple-macosx10.14.0 %s
   2 // RUN: %clang_cc1 -verify -std=c++2a -fsyntax-only -triple x86_64-apple-macosx10.14.0 %s -fno-signed-char
   3
   4 #if !__has_builtin(__builtin_bit_cast)
   5 #error
   6 #endif
   7
   8 template <class T, T v>
   9 T instantiate() {
  10   return __builtin_bit_cast(T, v);
  11 }
  12
  13 int x = instantiate<int, 32>();
  14
  15 struct secret_ctor {
  16   char member;
  17
  18 private: secret_ctor() = default;
  19 };
  20
  21 void test1() {
  22   secret_ctor c = __builtin_bit_cast(secret_ctor, (char)0);
  23 }
  24
  25 void test2() {
  26   constexpr int i = 0;
  27   // expected-error@+1{{__builtin_bit_cast source size does not equal destination size (4 vs 1)}}
  28   constexpr char c = __builtin_bit_cast(char, i);
  29 }
  30
  31 struct not_trivially_copyable {
  32   virtual void foo() {}
  33 };
  34
  35 // expected-error@+1{{__builtin_bit_cast source type must be trivially copyable}}
  36 constexpr unsigned long ul = __builtin_bit_cast(unsigned long, not_trivially_copyable{});
  37
  38 // expected-error@+1 {{__builtin_bit_cast destination type must be trivially copyable}}
  39 constexpr long us = __builtin_bit_cast(unsigned long &, 0L);
  40
  41 namespace PR42936 {
  42 template <class T> struct S { int m; };
  43
  44 extern S<int> extern_decl;
  45
  46 int x = __builtin_bit_cast(int, extern_decl);
  47 S<char> y = __builtin_bit_cast(S<char>, 0);
  48 }