clang/test/SemaCXX/empty-class-layout.cpp

   1 // RUN: %clang_cc1 -triple x86_64-unknown-unknown %s -fsyntax-only -verify -Wno-inaccessible-base
   2 // expected-no-diagnostics
   3
   4 #define SA(n, p) int a##n[(p) ? 1 : -1]
   5
   6 namespace Test0 {
   7
   8 struct A { int a; };
   9 SA(0, sizeof(A) == 4);
  10
  11 struct B { };
  12 SA(1, sizeof(B) == 1);
  13
  14 struct C : A, B { };
  15 SA(2, sizeof(C) == 4);
  16
  17 struct D { };
  18 struct E : D { };
  19 struct F : E { };
  20
  21 struct G : E, F { };
  22 SA(3, sizeof(G) == 2);
  23
  24 struct Empty { Empty(); };
  25
  26 struct I : Empty {
  27   Empty e;
  28 };
  29 SA(4, sizeof(I) == 2);
  30
  31 struct J : Empty {
  32   Empty e[2];
  33 };
  34 SA(5, sizeof(J) == 3);
  35
  36 template<int N> struct Derived : Empty, Derived<N - 1> {
  37 };
  38 template<> struct Derived<0> : Empty { };
  39
  40 struct S1 : virtual Derived<10> {
  41   Empty e;
  42 };
  43 SA(6, sizeof(S1) == 24);
  44
  45 struct S2 : virtual Derived<10> {
  46   Empty e[2];
  47 };
  48 SA(7, sizeof(S2) == 24);
  49
  50 struct S3 {
  51   Empty e;
  52 };
  53
  54 struct S4 : Empty, S3 {
  55 };
  56 SA(8, sizeof(S4) == 2);
  57
  58 struct S5 : S3, Empty {};
  59 SA(9, sizeof(S5) == 2);
  60
  61 struct S6 : S5 { };
  62 SA(10, sizeof(S6) == 2);
  63
  64 struct S7 : Empty {
  65   void *v;
  66 };
  67 SA(11, sizeof(S7) == 8);
  68
  69 struct S8 : Empty, A {
  70 };
  71 SA(12, sizeof(S8) == 4);
  72
  73 }
  74
  75 namespace Test1 {
  76
  77 // Test that we don't try to place both A subobjects at offset 0.
  78 struct A { };
  79 class B { virtual void f(); };
  80 class C : A, virtual B { };
  81 struct D : virtual C { };
  82 struct E : virtual A { };
  83 class F : D, E { };
  84
  85 SA(0, sizeof(F) == 24);
  86
  87 }
  88
  89 namespace Test2 {
  90
  91 // Test that B::a isn't laid out at offset 0.
  92 struct Empty { };
  93 struct A : Empty { };
  94 struct B : Empty {
  95   A a;
  96 };
  97
  98 SA(0, sizeof(B) == 2);
  99
 100 }
 101
 102 namespace Test3 {
 103
 104 // Test that B::a isn't laid out at offset 0.
 105 struct Empty { };
 106 struct A { Empty e; };
 107 struct B : Empty { A a; };
 108 SA(0, sizeof(B) == 2);
 109
 110 }
 111
 112 namespace Test4 {
 113
 114 // Test that C::Empty isn't laid out at offset 0.
 115 struct Empty { };
 116 struct A : Empty { };
 117 struct B { A a; };
 118 struct C : B, Empty { };
 119 SA(0, sizeof(C) == 2);
 120
 121 }
 122
 123 namespace Test5 {
 124
 125 // Test that B::Empty isn't laid out at offset 0.
 126 struct Empty { };
 127 struct Field : virtual Empty { };
 128 struct A {
 129   Field f;
 130 };
 131 struct B : A, Empty { };
 132 SA(0, sizeof(B) == 16);
 133
 134 }
 135
 136 namespace Test6 {
 137
 138 // Test that B::A isn't laid out at offset 0.
 139 struct Empty { };
 140 struct Field : virtual Empty { };
 141 struct A {
 142   Field f;
 143 };
 144 struct B : Empty, A { };
 145 SA(0, sizeof(B) == 16);
 146
 147 }
 148
 149 namespace Test7 {
 150   // Make sure we reserve enough space for both bases; PR11745.
 151   struct Empty { };
 152   struct Base1 : Empty { };
 153   struct Base2 : Empty { };
 154   struct Test : Base1, Base2 {
 155     char c;
 156   };
 157   SA(0, sizeof(Test) == 2);
 158 }
 159
 160 namespace Test8 {
 161   // Test that type sugar doesn't make us incorrectly determine the size of an
 162   // array of empty classes.
 163   struct Empty1 {};
 164   struct Empty2 {};
 165   struct Empties : Empty1, Empty2 {};
 166   typedef Empty1 Sugar[4];
 167   struct A : Empty2, Empties {
 168     // This must go at offset 2, because if it were at offset 0,
 169     // V[0][1] would overlap Empties::Empty1.
 170     Sugar V[1];
 171   };
 172   SA(0, sizeof(A) == 6);
 173 }