1 // RUN: %clang_cc1 -std=c++1z -verify=ref,both %s -fcxx-exceptions -triple=x86_64-linux-gnu 2 // RUN: %clang_cc1 -std=c++1z -verify=expected,both %s -fcxx-exceptions -triple=x86_64-linux-gnu -fexperimental-new-constant-interpreter 3 4 // both-no-diagnostics 5 namespace EvalOrder { 6 template<typename T> struct lvalue { 7 T t; 8 constexpr T &get() { return t; } 9 }; 10 11 struct UserDefined { 12 int n = 0; 13 constexpr UserDefined &operator=(const UserDefined&) { return *this; } 14 constexpr UserDefined &operator+=(const UserDefined&) { return *this; } 15 constexpr void operator<<(const UserDefined&) const {} 16 constexpr void operator>>(const UserDefined&) const {} 17 constexpr void operator+(const UserDefined&) const {} 18 constexpr void operator[](int) const {} 19 }; 20 constexpr UserDefined ud; 21 22 struct NonMember {}; 23 constexpr void operator+=(NonMember, NonMember) {} 24 constexpr void operator<<(NonMember, NonMember) {} 25 constexpr void operator>>(NonMember, NonMember) {} 26 constexpr void operator+(NonMember, NonMember) {} 27 constexpr NonMember nm; 28 29 constexpr void f(...) {} 30 31 // Helper to ensure that 'a' is evaluated before 'b'. 32 struct seq_checker { 33 bool done_a = false; 34 bool done_b = false; 35 36 template <typename T> constexpr T &&a(T &&v) { 37 done_a = true; 38 return (T &&)v; 39 } 40 template <typename T> constexpr T &&b(T &&v) { 41 if (!done_a) 42 throw "wrong"; 43 done_b = true; 44 return (T &&)v; 45 } 46 47 constexpr bool ok() { return done_a && done_b; } 48 }; 49 50 // SEQ(expr), where part of the expression is tagged A(...) and part is 51 // tagged B(...), checks that A is evaluated before B. 52 #define A sc.a 53 #define B sc.b 54 #define SEQ(...) static_assert([](seq_checker sc) { void(__VA_ARGS__); return sc.ok(); }({})) 55 56 // Longstanding sequencing rules. 57 SEQ((A(1), B(2))); 58 SEQ((A(true) ? B(2) : throw "huh?")); 59 SEQ((A(false) ? throw "huh?" : B(2))); 60 SEQ(A(true) && B(true)); 61 SEQ(A(false) || B(true)); 62 63 // From P0145R3: 64 65 // Rules 1 and 2 have no effect ('b' is not an expression). 66 67 // Rule 3: a->*b 68 SEQ(A(ud).*B(&UserDefined::n)); 69 SEQ(A(&ud)->*B(&UserDefined::n)); 70 71 // Rule 4: a(b1, b2, b3) 72 SEQ(A(f)(B(1), B(2), B(3))); 73 74 // Rule 5: b = a, b @= a 75 SEQ(B(lvalue<int>().get()) = A(0)); 76 SEQ(B(lvalue<UserDefined>().get()) = A(ud)); 77 SEQ(B(lvalue<int>().get()) += A(0)); 78 SEQ(B(lvalue<UserDefined>().get()) += A(ud)); 79 SEQ(B(lvalue<NonMember>().get()) += A(nm)); 80 81 // Rule 6: a[b] 82 constexpr int arr[3] = {}; 83 SEQ(A(arr)[B(0)]); 84 SEQ(A(+arr)[B(0)]); 85 SEQ(A(0)[B(arr)]); 86 SEQ(A(0)[B(+arr)]); 87 88 SEQ(A(ud)[B(0)]); 89 90 // Rule 7: a << b 91 SEQ(A(1) << B(2)); 92 SEQ(A(ud) << B(ud)); 93 SEQ(A(nm) << B(nm)); 94 95 // Rule 8: a >> b 96 SEQ(A(1) >> B(2)); 97 SEQ(A(ud) >> B(ud)); 98 SEQ(A(nm) >> B(nm)); 99 100 // No particular order of evaluation is specified in other cases, but we in 101 // practice evaluate left-to-right. 102 // FIXME: Technically we're expected to check for undefined behavior due to 103 // unsequenced read and modification and treat it as non-constant due to UB. 104 SEQ(A(1) + B(2)); 105 SEQ(A(ud) + B(ud)); 106 SEQ(A(nm) + B(nm)); 107 SEQ(f(A(1), B(2))); 108 #undef SEQ 109 #undef A 110 #undef B 111 } 112