vtableのメモリレイアウトの調査

gistfile1.txt

t1  [004191A8] sizeof: 1
t2a [004191A4] sizeof: 4, a: 004191A4
t2b [00419190] sizeof: 8, a: 00419190, b: 00419194
t3a [004191A0] sizeof: 4, a: 004191A0
t3b [00419198] sizeof: 8, a: 00419198, b: 0041919C
t4a1[004191CC] sizeof: 8, a: 004191D0
t4a2[004191AC] sizeof: 8, a: 004191B0
t4b1[004191C0] sizeof: 12, a: 004191C4, b: 004191C8
t4b2[004191B4] sizeof: 12, a: 004191B8, b: 004191BC

t3a [004191A0] Test3A.test1: 00411104
t3b [00419198] Test3B.test1: 004110FF
t4a1[004191CC] 00416AA0 -> 00411217, Test4A.test1: 00411181
t4a2[004191AC] 00416AA0 -> 00411217, Test4A.test1: 00411181
t4b1[004191C0] 00416AAC -> 00411212, Test4B.test1: 00411181
t4b2[004191B4] 00416AAC -> 00411212, Test4B.test1: 00411181

vtable.cpp

#include <stdio.h>

struct Test1 {
} t1;

struct Test2A {
    int a;
} t2a;

struct Test2B : Test2A {
    int b;
} t2b;

struct Test3A {
    int a;
    void test1() {}
} t3a;

struct Test3B : Test3A {
    int b;
    void test1() {}
    void test2() {}
} t3b;

struct Test4A {
    int a;
    virtual void test1() {}
} t4a1, t4a2;

struct Test4B : Test4A {
    int b;
    virtual void test1() {}
    virtual void test2() {}
} t4b1, t4b2;

int main() {
    printf("t1  [%p] sizeof: %d\n", &t1, sizeof(t1));
    printf("t2a [%p] sizeof: %d, a: %p\n", &t2a, sizeof(t2a), &t2a.a);
    printf("t2b [%p] sizeof: %d, a: %p, b: %p\n", &t2b, sizeof(t2b), &t2b.a, &t2b.b);
    printf("t3a [%p] sizeof: %d, a: %p\n", &t3a, sizeof(t3a), &t3a.a);
    printf("t3b [%p] sizeof: %d, a: %p, b: %p\n", &t3b, sizeof(t3b), &t3b.a, &t3b.b);
    printf("t4a1[%p] sizeof: %d, a: %p\n", &t4a1, sizeof(t4a1), &t4a1.a);
    printf("t4a2[%p] sizeof: %d, a: %p\n", &t4a2, sizeof(t4a2), &t4a2.a);
    printf("t4b1[%p] sizeof: %d, a: %p, b: %p\n", &t4b1, sizeof(t4b1), &t4b1.a, &t4b1.b);
    printf("t4b2[%p] sizeof: %d, a: %p, b: %p\n", &t4b2, sizeof(t4b2), &t4b2.a, &t4b2.b);
    printf("\n");
    printf("t3a [%p] Test3A.test1: %p\n", &t3a, &Test3A::test1);
    printf("t3b [%p] Test3B.test1: %p\n", &t3b, &Test3B::test1);
    auto pt4a1 = (void ***)&t4a1;
    printf("t4a1[%p] %p -> %p, Test4A.test1: %p\n", pt4a1, *pt4a1, **pt4a1, &Test4A::test1);
    auto pt4a2 = (void ***)&t4a2;
    printf("t4a2[%p] %p -> %p, Test4A.test1: %p\n", pt4a2, *pt4a2, **pt4a2, &Test4A::test1);
    auto pt4b1 = (void ***)&t4b1;
    printf("t4b1[%p] %p -> %p, Test4B.test1: %p\n", pt4b1, *pt4b1, **pt4b1, &Test4B::test1);
    auto pt4b2 = (void ***)&t4b2;
    printf("t4b2[%p] %p -> %p, Test4B.test1: %p\n", pt4b2, *pt4b2, **pt4b2, &Test4B::test1);
}