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[MS ABI] Implement __declspec(empty_bases) and __declspec(layout_version) The layout_version attribute is pretty straightforward: use the layout rules from version XYZ of MSVC when used like struct __declspec(layout_version(XYZ)) S {}; The empty_bases attribute is more interesting. It tries to get the C++ empty base optimization to fire more often by tweaking the MSVC ABI rules in subtle ways: 1. Disable the leading and trailing zero-sized object flags if a class is marked __declspec(empty_bases) and is empty. This means that given: struct __declspec(empty_bases) A {}; struct __declspec(empty_bases) B {}; struct C : A, B {}; 'C' will have size 1 and nvsize 0 despite not being annotated __declspec(empty_bases). 2. When laying out virtual or non-virtual bases, disable the injection of padding between classes if the most derived class is marked __declspec(empty_bases). This means that given: struct A {}; struct B {}; struct __declspec(empty_bases) C : A, B {}; 'C' will have size 1 and nvsize 0. 3. When calculating the offset of a non-virtual base, choose offset zero if the most derived class is marked __declspec(empty_bases) and the base is empty _and_ has an nvsize of 0. Because of the ABI rules, this does not mean that empty bases reliably get placed at offset 0! For example: struct A {}; struct B {}; struct __declspec(empty_bases) C : A, B { virtual ~C(); }; 'C' will be pointer sized to account for the vfptr at offset 0. 'A' and 'B' will _not_ be at offset 0 despite being empty! Instead, they will be located right after the vfptr. This occurs due to the interaction betweeen non-virtual base layout and virtual function pointer injection: injection occurs after the nv-bases and shifts them down by the size of a pointer. llvm-svn: 270457
2016-05-24 01:16:12 +08:00
// RUN: %clang_cc1 -fno-rtti -emit-llvm-only -triple i686-pc-win32 -fms-extensions -fdump-record-layouts -fsyntax-only %s 2>/dev/null \
// RUN: | FileCheck %s
// RUN: %clang_cc1 -fno-rtti -emit-llvm-only -triple x86_64-pc-win32 -fms-extensions -fdump-record-layouts -fsyntax-only %s 2>/dev/null \
// RUN: | FileCheck %s
namespace test1 {
struct A {
int a;
};
struct B {
int b;
};
struct C {};
struct __declspec(align(16)) D {};
struct __declspec(empty_bases) X : A, D, B, C {
};
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test1::A
// CHECK-NEXT: 0 | int a
// CHECK-NEXT: | [sizeof=4, align=4,
// CHECK-NEXT: | nvsize=4, nvalign=4]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test1::D (empty)
// CHECK-NEXT: | [sizeof=16, align=16,
// CHECK-NEXT: | nvsize=0, nvalign=16]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test1::B
// CHECK-NEXT: 0 | int b
// CHECK-NEXT: | [sizeof=4, align=4,
// CHECK-NEXT: | nvsize=4, nvalign=4]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test1::C (empty)
// CHECK-NEXT: | [sizeof=1, align=1,
// CHECK-NEXT: | nvsize=0, nvalign=1]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test1::X
// CHECK-NEXT: 0 | struct test1::A (base)
// CHECK-NEXT: 0 | int a
// CHECK-NEXT: 0 | struct test1::D (base) (empty)
// CHECK-NEXT: 0 | struct test1::C (base) (empty)
// CHECK-NEXT: 4 | struct test1::B (base)
// CHECK-NEXT: 4 | int b
// CHECK-NEXT: | [sizeof=16, align=16,
// CHECK-NEXT: | nvsize=16, nvalign=16]
int _ = sizeof(X);
}
namespace test2 {
struct A {
int a;
};
struct __declspec(empty_bases) B {};
struct C : A {
B b;
};
struct D {};
struct E {
int e;
};
struct F : D, E {};
struct G : C, F {};
int _ = sizeof(G);
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test2::A
// CHECK-NEXT: 0 | int a
// CHECK-NEXT: | [sizeof=4, align=4,
// CHECK-NEXT: | nvsize=4, nvalign=4]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test2::B (empty)
// CHECK-NEXT: | [sizeof=1, align=1,
// CHECK-NEXT: | nvsize=0, nvalign=1]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test2::C
// CHECK-NEXT: 0 | struct test2::A (base)
// CHECK-NEXT: 0 | int a
// CHECK-NEXT: 4 | struct test2::B b (empty)
// CHECK-NEXT: | [sizeof=8, align=4,
// CHECK-NEXT: | nvsize=8, nvalign=4]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test2::D (empty)
// CHECK-NEXT: | [sizeof=1, align=1,
// CHECK-NEXT: | nvsize=0, nvalign=1]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test2::E
// CHECK-NEXT: 0 | int e
// CHECK-NEXT: | [sizeof=4, align=4,
// CHECK-NEXT: | nvsize=4, nvalign=4]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test2::F
// CHECK-NEXT: 0 | struct test2::D (base) (empty)
// CHECK-NEXT: 0 | struct test2::E (base)
// CHECK-NEXT: 0 | int e
// CHECK-NEXT: | [sizeof=4, align=4,
// CHECK-NEXT: | nvsize=4, nvalign=4]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test2::G
// CHECK-NEXT: 0 | struct test2::C (base)
// CHECK-NEXT: 0 | struct test2::A (base)
// CHECK-NEXT: 0 | int a
// CHECK-NEXT: 4 | struct test2::B b (empty)
// CHECK-NEXT: 8 | struct test2::F (base)
// CHECK-NEXT: 8 | struct test2::D (base) (empty)
// CHECK-NEXT: 8 | struct test2::E (base)
// CHECK-NEXT: 8 | int e
// CHECK-NEXT: | [sizeof=12, align=4,
// CHECK-NEXT: | nvsize=12, nvalign=4]
}
namespace test3 {
struct A {
int a;
};
struct B {};
struct C : A {
B b;
};
struct D {};
struct E {
int e;
};
struct F : D, E {};
struct __declspec(empty_bases) G : C, F {};
int _ = sizeof(G);
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test3::A
// CHECK-NEXT: 0 | int a
// CHECK-NEXT: | [sizeof=4, align=4,
// CHECK-NEXT: | nvsize=4, nvalign=4]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test3::B (empty)
// CHECK-NEXT: | [sizeof=1, align=1,
// CHECK-NEXT: | nvsize=0, nvalign=1]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test3::C
// CHECK-NEXT: 0 | struct test3::A (base)
// CHECK-NEXT: 0 | int a
// CHECK-NEXT: 4 | struct test3::B b (empty)
// CHECK-NEXT: | [sizeof=8, align=4,
// CHECK-NEXT: | nvsize=8, nvalign=4]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test3::D (empty)
// CHECK-NEXT: | [sizeof=1, align=1,
// CHECK-NEXT: | nvsize=0, nvalign=1]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test3::E
// CHECK-NEXT: 0 | int e
// CHECK-NEXT: | [sizeof=4, align=4,
// CHECK-NEXT: | nvsize=4, nvalign=4]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test3::F
// CHECK-NEXT: 0 | struct test3::D (base) (empty)
// CHECK-NEXT: 0 | struct test3::E (base)
// CHECK-NEXT: 0 | int e
// CHECK-NEXT: | [sizeof=4, align=4,
// CHECK-NEXT: | nvsize=4, nvalign=4]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test3::G
// CHECK-NEXT: 0 | struct test3::C (base)
// CHECK-NEXT: 0 | struct test3::A (base)
// CHECK-NEXT: 0 | int a
// CHECK-NEXT: 4 | struct test3::B b (empty)
// CHECK-NEXT: 8 | struct test3::F (base)
// CHECK-NEXT: 8 | struct test3::D (base) (empty)
// CHECK-NEXT: 8 | struct test3::E (base)
// CHECK-NEXT: 8 | int e
// CHECK-NEXT: | [sizeof=12, align=4,
// CHECK-NEXT: | nvsize=12, nvalign=4]
}
namespace test4 {
struct A {
int a;
};
struct B {};
struct C : A {
B b;
};
struct __declspec(empty_bases) D {};
struct E {
int e;
};
struct F : D, E {};
struct G : C, F {};
int _ = sizeof(G);
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test4::A
// CHECK-NEXT: 0 | int a
// CHECK-NEXT: | [sizeof=4, align=4,
// CHECK-NEXT: | nvsize=4, nvalign=4]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test4::B (empty)
// CHECK-NEXT: | [sizeof=1, align=1,
// CHECK-NEXT: | nvsize=0, nvalign=1]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test4::C
// CHECK-NEXT: 0 | struct test4::A (base)
// CHECK-NEXT: 0 | int a
// CHECK-NEXT: 4 | struct test4::B b (empty)
// CHECK-NEXT: | [sizeof=8, align=4,
// CHECK-NEXT: | nvsize=8, nvalign=4]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test4::D (empty)
// CHECK-NEXT: | [sizeof=1, align=1,
// CHECK-NEXT: | nvsize=0, nvalign=1]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test4::E
// CHECK-NEXT: 0 | int e
// CHECK-NEXT: | [sizeof=4, align=4,
// CHECK-NEXT: | nvsize=4, nvalign=4]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test4::F
// CHECK-NEXT: 0 | struct test4::D (base) (empty)
// CHECK-NEXT: 0 | struct test4::E (base)
// CHECK-NEXT: 0 | int e
// CHECK-NEXT: | [sizeof=4, align=4,
// CHECK-NEXT: | nvsize=4, nvalign=4]
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct test4::G
// CHECK-NEXT: 0 | struct test4::C (base)
// CHECK-NEXT: 0 | struct test4::A (base)
// CHECK-NEXT: 0 | int a
// CHECK-NEXT: 4 | struct test4::B b (empty)
// CHECK-NEXT: 8 | struct test4::F (base)
// CHECK-NEXT: 8 | struct test4::D (base) (empty)
// CHECK-NEXT: 8 | struct test4::E (base)
// CHECK-NEXT: 8 | int e
// CHECK-NEXT: | [sizeof=12, align=4,
// CHECK-NEXT: | nvsize=12, nvalign=4]
}