Multiple Inheritance Memory layout analysis

VC + + 2005/GD//acronym (Root level) = RL//acronym (Second level) = SL//acronym (Third level) = TL #include <stdio .h> typedef void (*VFUNCPTR) (); typedef vfuncptr* VTable; Class RL1 {public:virtual void Vf_rl1 () {} public:int _i_rl1;}; Class RL2 {public:int _i_rl2;}; Class RL3 {public:virtual void Vf_rl3 () {} public:int _i_rl3;}; Class Sl1:public RL1, public RL2, public RL3 {public:int _I_SL1; Class Sl2:public RL1, public RL2, public RL3 {public:virtual void Vf_sl2 () {} public:int _I_SL2; Class Sl3:public RL2, public RL3 {public:int _i_sl3;}; Class Sl4:public RL2, public RL3 {public:virtual void Vf_sl4 () {} public:int _i_sl4;}; To analyze this, SL1 and SL2 are better off using virtual inheritance. Do it again when you are free. Class TL://Public SL1, public SL2//{//public://virtual void Vf_tl () {}//public://int _i_tl;//}; int main () {RL1 rl1; rl1._i_rl1 = 0x11; int RL1::* pdm_rl1 = NULL; pdm_rl1 = &RL1::_i_rl1; printf ("0x%p:0x%x/n", pdm_ RL1, RL1.*PDM_RL1); void (RL1::* pmf_rl1) () = &rl1::vf_RL1; QuickWatch identifier PMF_RL1, associated with thunk. printf ("&AMP;RL1::VF_RL1:%p/n", PMF_RL1); The printed value is not the same as the value in the virtual function table, WHY? VTable vt_rl1 = * (vtable*) &rl1; In the Watch window, see the contents of the VT_RL1 subscript from 50//to 200. Note: Pay attention to vt_rl1[-1], and RTTI related. printf ("--------------------------------/n"); RL2 Rl2; Rl2._i_rl2 = 0x22; VTable vt_rl2 = * (vtable*) &rl2; VT_RL2; printf ("--------------------------------/n"); RL3 Rl3; Rl3._i_rl3 = 0x33; VTable vt_rl3 = * (vtable*) &rl3; VT_RL3; printf ("--------------------------------/n"); SL1 SL1; SL1._I_RL1 = 0x11; Sl1._i_rl2 = 0x22; Sl1._i_rl3 = 0x33; SL1._I_SL1 = 0x1111; int SL1::* PDM_SL1 = NULL; PDM_SL1 = &SL1::_i_rl1; printf ("0x%p:0x%x/n", PDM_SL1, SL1.*PDM_SL1); PDM_SL1 = &SL1::_i_rl2; printf ("0x%p:0x%x/n", PDM_SL1, SL1.*PDM_SL1); PDM_SL1 = &SL1::_i_rl3; printf ("0x%p:0x%x/n", PDM_SL1, SL1.*PDM_SL1); PDM_SL1 = &SL1::_i_sl1; printf ("0x%p:0x%x/n", PDM_SL1, SL1.*PDM_SL1); Look at the Watch window: vt_sl1_1, 2 VTable vt_sl1_1 = * (vtable*) &sl1; InWatch window look: vt_sl1_2, 2 VTable vt_sl1_2 = * (vtable*) ((char*) &AMP;SL1 + sizeof (void*) + sizeof (int)); printf ("--------------------------------/n"); SL2 SL2; SL2._I_RL1 = 0x11; Sl2._i_rl2 = 0x22; Sl2._i_rl3 = 0x33; SL2._I_SL2 = 0x2222; int SL2::* PDM_SL2 = NULL; PDM_SL2 = &SL2::_i_rl1; printf ("0x%p:0x%x/n", PDM_SL2, SL2.*PDM_SL2); PDM_SL2 = &SL2::_i_rl2; printf ("0x%p:0x%x/n", PDM_SL2, SL2.*PDM_SL2); PDM_SL2 = &SL2::_i_rl3; printf ("0x%p:0x%x/n", PDM_SL2, SL2.*PDM_SL2); PDM_SL2 = &SL2::_i_sl2; printf ("0x%p:0x%x/n", PDM_SL2, SL2.*PDM_SL2); Look at the Watch window: vt_sl2_1, 3 VTable vt_sl2_1 = * (vtable*) &sl2; Look at the Watch window: vt_sl2_2, 2 VTable vt_sl2_2 = * (vtable*) ((char*) &AMP;SL2 + sizeof (void*) + sizeof (int)); printf ("--------------------------------/n"); SL3 SL3; Sl3._i_rl2 = 0x22; Sl3._i_rl3 = 0x33; SL3._I_SL3 = 0x3333; int SL3::* pdm_sl3 = NULL; PDM_SL3 = &SL3::_i_rl2; printf ("0x%p:0x%x/n", PDM_SL3, SL3.*PDM_SL3); PDM_SL3 = &SL3::_i_rl3; printf ("0x%p:0x%x/n", pdm_SL3, SL3.*PDM_SL3); PDM_SL3 = &SL3::_i_sl3; printf ("0x%p:0x%x/n", PDM_SL3, SL3.*PDM_SL3); Look at the Watch window: VT_SL3, 2 VTable vt_sl3 = * (vtable*) &sl3; printf ("--------------------------------/n"); SL4 SL4; Sl4._i_rl2 = 0x22; Sl4._i_rl3 = 0x33; SL4._I_SL4 = 0x4444; int SL4::* pdm_sl4 = NULL; PDM_SL4 = &SL4::_i_rl2; printf ("0x%p:0x%x/n", PDM_SL4, SL4.*PDM_SL4); PDM_SL4 = &SL4::_i_rl3; printf ("0x%p:0x%x/n", PDM_SL4, SL4.*PDM_SL4); PDM_SL4 = &SL4::_i_sl4; printf ("0x%p:0x%x/n", PDM_SL4, SL4.*PDM_SL4); Look at the Watch window: VT_SL4, 3 VTable vt_sl4 = * (vtable*) &sl4; printf ("--------------------------------/n"); return 0; }

0x00000004:0x11 &rl1::vf_rl1:0041110e--------------------------------0x00000004:0x11 0x00000010:0x22 0x0000000c:0x33 0x00000014:0x1111--------------------------------0x00000004:0x11 0x00000010:0x22 0x0000000c:0x33 0 x00000014:0x2222--------------------------------0x00000008:0x22 0x00000004:0x33 0x0000000c:0x3333--------------- -----------------0x00000008:0x22 0x00000004:0x33 0x0000000c:0x4444--------------------------------

Analysis results:
1. SL1 Object

2. SL2 Object

3. SL3 Object

4. SL4 Object