clang/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p5.cpp

   1 // RUN: %clang_cc1 -fsyntax-only -triple x86_64-unknown-unknown -verify -std=c++11 -fcxx-exceptions %s
   2 // RUN: %clang_cc1 -fsyntax-only -triple x86_64-unknown-unknown -verify -std=c++14 -fcxx-exceptions %s
   3 // RUN: %clang_cc1 -fsyntax-only -triple x86_64-unknown-unknown -std=c++11 -fcxx-exceptions -Wno-invalid-constexpr %s -DNO_INVALID_CONSTEXPR
   4
   5 namespace StdExample {
   6
   7 constexpr int f(void *) { return 0; }
   8 constexpr int f(...) { return 1; }
   9 constexpr int g1() { return f(0); }
  10 constexpr int g2(int n) { return f(n); }
  11 constexpr int g3(int n) { return f(n*0); }
  12
  13 namespace N {
  14   constexpr int c = 5;
  15   constexpr int h() { return c; }
  16 }
  17 constexpr int c = 0;
  18 constexpr int g4() { return N::h(); }
  19
  20 static_assert(f(0) == 0, "");
  21 static_assert(f('0') == 1, "");
  22 static_assert(g1() == 0, "");
  23 static_assert(g2(0) == 1, "");
  24 static_assert(g2(1) == 1, "");
  25 static_assert(g3(0) == 1, "");
  26 static_assert(g3(1) == 1, "");
  27 static_assert(N::h() == 5, "");
  28 static_assert(g4() == 5, "");
  29
  30
  31 constexpr int f(bool b)
  32   { return b ? throw 0 : 0; } // ok
  33 constexpr int f() { return throw 0, 0; } // expected-error {{constexpr function never produces a constant expression}} expected-note {{subexpression}}
  34
  35 struct B {
  36   constexpr B(int x) : i(0) { }
  37   int i;
  38 };
  39
  40 int global; // expected-note {{declared here}}
  41
  42 struct D : B {
  43   constexpr D() : B(global) { } // expected-error {{constexpr constructor never produces a constant expression}} expected-note {{read of non-const}}
  44 };
  45
  46 }
  47
  48 namespace PotentialConstant {
  49
  50 constexpr int Comma(int n) { return // expected-error {{constexpr function never produces a constant expression}}
  51   (void)(n * 2),
  52   throw 0, // expected-note {{subexpression}}
  53   0;
  54 }
  55
  56 int ng; // expected-note 6{{here}}
  57 constexpr int BinaryOp1(int n) { return n + ng; } // expected-error {{never produces}} expected-note {{read}}
  58 constexpr int BinaryOp2(int n) { return ng + n; } // expected-error {{never produces}} expected-note {{read}}
  59
  60 double dg; // expected-note 2{{here}}
  61 constexpr double BinaryOp1(double d) { return d + dg; } // expected-error {{never produces}} expected-note {{read}}
  62 constexpr double BinaryOp2(double d) { return dg + d; } // expected-error {{never produces}} expected-note {{read}}
  63
  64 constexpr int Add(int a, int b, int c) { return a + b + c; }
  65 constexpr int FunctionArgs(int a) { return Add(a, ng, a); } // expected-error {{never produces}} expected-note {{read}}
  66
  67 struct S { int a; int b; int c[2]; };
  68 constexpr S InitList(int a) { return { a, ng }; }; // expected-error {{never produces}} expected-note {{read}}
  69 constexpr S InitList1a(int a) { return S{ a, ng }; }; // expected-error {{never produces}} expected-note {{read}}
  70 constexpr S InitList2(int a) { return { a, a, { ng } }; }; // expected-error {{never produces}} expected-note {{read}}
  71 constexpr S InitList3(int a) { return a ? S{ a, a } : S{ a, ng }; }; // ok
  72
  73 constexpr int LogicalAnd1(int n) { return n && (throw, 0); } // ok
  74 constexpr int LogicalAnd2(int n) { return 1 && (throw, 0); } // expected-error {{never produces}} expected-note {{subexpression}}
  75
  76 constexpr int LogicalOr1(int n) { return n || (throw, 0); } // ok
  77 constexpr int LogicalOr2(int n) { return 0 || (throw, 0); } // expected-error {{never produces}} expected-note {{subexpression}}
  78
  79 constexpr int Conditional1(bool b, int n) { return b ? n : ng; } // ok
  80 constexpr int Conditional2(bool b, int n) { return b ? n * ng : n + ng; } // expected-error {{never produces}} expected-note {{both arms of conditional operator are unable to produce a constant expression}}
  81
  82 // __builtin_constant_p ? : is magical, and is always a potential constant.
  83 constexpr bool BcpCall(int n) {
  84   return __builtin_constant_p((int*)n != &n) ? (int*)n != &n : (int*)n != &n; // expected-warning 3 {{cast to 'int *' from smaller integer type 'int'}}
  85 }
  86 static_assert(BcpCall(0), "");
  87
  88 // DR1311: A function template which can produce a constant expression, but
  89 // for which a particular specialization cannot, is ok.
  90 template<typename T> constexpr T cmin(T a, T b) {
  91   return a < b ? a : b;
  92 }
  93 int n = cmin(3, 5); // ok
  94
  95 struct X {
  96   constexpr X() {}
  97   bool operator<(X); // not constexpr
  98 };
  99
 100 X x = cmin(X(), X()); // ok, not constexpr
 101
 102 // Same with other temploids.
 103 template<typename T>
 104 struct Y {
 105   constexpr Y() {}
 106   constexpr int get() { return T(); }
 107 #if __cplusplus < 201402L
 108   // expected-warning@-2 {{C++14}}
 109 #endif
 110 };
 111 struct Z { operator int(); };
 112
 113 int y1 = Y<int>().get(); // ok
 114 int y2 = Y<Z>().get(); // ok
 115
 116 }
 117
 118 #ifndef NO_INVALID_CONSTEXPR
 119 namespace PR14550 {
 120   // As an "extension", we allow functions which can't produce constant
 121   // expressions to be declared constexpr in system headers (libstdc++
 122   // marks some functions as constexpr which use builtins which we don't
 123   // support constant folding). Ensure that we don't mark those functions
 124   // as invalid after suppressing the diagnostic.
 125 # 126 "p5.cpp" 1 3
 126   int n;
 127   struct A {
 128     static constexpr int f() { return n; }
 129   };
 130   template<typename T> struct B {
 131     B() { g(T::f()); } // expected-error {{undeclared identifier 'g'}}
 132   };
 133 # 134 "p5.cpp" 2
 134   template class B<A>; // expected-note {{here}}
 135 }
 136 #endif
 137
 138 #if __cplusplus >= 201402L
 139 constexpr void f() { throw; } // expected-error {{never produces}} expected-note {{subexpression}}
 140 #endif