clang/test/Layout/watchos-standard-layout.cpp

   1 // RUN: %clang_cc1 -fsyntax-only -triple armv7k-apple-darwin-watchos -fdump-record-layouts %s | FileCheck %s
   2
   3 // WatchOS, 64-bit iOS, and WebAssembly use the C++11 definition of POD to
   4 // determine whether we can reuse the tail padding of a struct (POD is
   5 // "trivially copyable and standard layout"). The definition of standard
   6 // layout changed some time around C++17; check that we still use the old
   7 // ABI rule.
   8
   9 // B is not standard-layout, but it was under C++11's rule, so we pack
  10 // C::d into its tail padding anyway.
  11 struct A { int : 0; };
  12 struct B : A { int n; char c[3]; };
  13 struct C : B { char d; };
  14 int c = sizeof(C);
  15 static_assert(!__is_standard_layout(B));
  16
  17 // CHECK:*** Dumping AST Record Layout
  18 // CHECK:          0 | struct C
  19 // CHECK-NEXT:     0 |   struct B (base)
  20 // CHECK-NEXT:     0 |     struct A (base) (empty)
  21 // CHECK-NEXT:   0:- |       int
  22 // CHECK-NEXT:     0 |     int n
  23 // CHECK-NEXT:     4 |     char[3] c
  24 // CHECK-NEXT:     8 |   char d
  25 // CHECK-NEXT:       | [sizeof=12, dsize=9, align=4,
  26 // CHECK-NEXT:       |  nvsize=9, nvalign=4]
  27
  28 // F is not standard-layout due to the repeated D base class, but it was under
  29 // C++11's rule, so we pack G::d into its tail padding anyway.
  30 struct D {};
  31 struct E : D {};
  32 struct F : D, E { int n; char c[3]; };
  33 struct G : F { G(const G&); char d; };
  34 int g = sizeof(G);
  35 static_assert(!__is_standard_layout(F));
  36
  37 // CHECK:*** Dumping AST Record Layout
  38 // CHECK:          0 | struct G
  39 // CHECK-NEXT:     0 |   struct F (base)
  40 // CHECK-NEXT:     0 |     struct D (base) (empty)
  41 // CHECK-NEXT:     1 |     struct E (base) (empty)
  42 // CHECK-NEXT:     1 |       struct D (base) (empty)
  43 // CHECK-NEXT:     0 |     int n
  44 // CHECK-NEXT:     4 |     char[3] c
  45 // CHECK-NEXT:     8 |   char d
  46 // CHECK-NEXT:       | [sizeof=12, dsize=9, align=4,
  47 // CHECK-NEXT:       |  nvsize=9, nvalign=4]