clang/test/SemaCXX/ms-constexpr.cpp

   1 // RUN: %clang_cc1 -fms-compatibility -fms-compatibility-version=19.33 -std=c++20 -verify %s
   2
   3 [[msvc::constexpr]] int log2(int x) { [[msvc::constexpr]] return x > 1 ? 1 + log2(x / 2) : 0; }
   4 constexpr bool test_log2() { [[msvc::constexpr]] return log2(32) == 5; }
   5 static_assert(test_log2());
   6
   7 [[msvc::constexpr]] int get_value(int x)
   8 {
   9   switch (x)
  10   {
  11     case 42: return 1337;
  12     default:
  13              if (x < 0) [[msvc::constexpr]] return log2(-x);
  14              else return x;
  15   }
  16 }
  17
  18 constexpr bool test_complex_expr() {
  19   [[msvc::constexpr]] return get_value(get_value(42) - 1337 + get_value(-32) - 5 + (get_value(1) ? get_value(0) : get_value(2))) == get_value(0);
  20 }
  21 static_assert(test_complex_expr());
  22
  23 constexpr bool get_constexpr_true() { return true; }
  24 [[msvc::constexpr]] bool get_msconstexpr_true() { return get_constexpr_true(); }
  25 constexpr bool test_get_msconstexpr_true() { [[msvc::constexpr]] return get_msconstexpr_true(); }
  26 static_assert(test_get_msconstexpr_true());
  27
  28 // TODO (#72149): Add support for [[msvc::constexpr]] constructor; this code is valid for MSVC.
  29 struct S2 {
  30     [[msvc::constexpr]] S2() {}
  31     [[msvc::constexpr]] bool value() { return true; }
  32     static constexpr bool check() { [[msvc::constexpr]] return S2{}.value(); } // expected-error {{constexpr function never produces a constant expression}} \
  33                                                                                // expected-note {{non-literal type 'S2' cannot be used in a constant expression}} \
  34                                                                                // expected-note {{non-literal type 'S2' cannot be used in a constant expression}}
  35 };
  36 static_assert(S2::check()); // expected-error {{static assertion expression is not an integral constant expression}} \
  37                             // expected-note {{in call to 'check()'}}