C++ 多重繼承 多態函數 內存佈局

 僅用於 VS 2008 環境：

class i_unknown { public: i_unknown() { printf("init base /r/n"); } virtual void queryinterface(int index, void** ppv) = 0; virtual void addref() = 0; virtual void release() = 0; }; class ca : public i_unknown { public: int ca_a; ca () { printf("init a /r/n"); ca_a = 1; } virtual void queryinterface(int index, void** ppv) { printf("ca_query!! /r/n"); }; virtual void addref(){}; virtual void release(){}; virtual void test_a() { printf("i am a /rn"); } }; class cb : public i_unknown { public: int cb_b; cb () { printf("init b /r/n"); cb_b = 2; } virtual void queryinterface(int index, void** ppv) { printf("cb_query!! /r/n"); } virtual void addref(){}; virtual void release(){}; virtual void test_b() { printf("i am c /r/n"); } }; class con: public ca, public cb { public: int con_i; con() { printf("init c /r/n"); con_i = 3; } virtual void qcon(void){}; virtual void queryinterface(int index, void** ppv) { printf("con_query !! /r/n"); if (index == 1) { *ppv = (ca*)this; } else if (index == 2) { *ppv = (cb*)this; } else { *ppv = (con*)this; } } virtual void addref(){}; virtual void release(){}; virtual void test_con() { printf("i am a && b /r/n"); } }; int _tmain(int argc, _TCHAR* argv[]) { void* tp1; void* tp2; void* tp3; con* p_bb = new con(); ca* p_a = new ca(); cb* p_b = new cb(); p_bb->queryinterface(1, &tp1); p_bb->queryinterface(2, &tp2); p_bb->queryinterface(3, &tp3); printf("tp1/tp2/tp3: 0x%x , 0x%x, 0x%x /r/n", tp1, tp2, tp3); getchar(); return 0; }

內存分佈說明：

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p_a :   vp_tbl  (4 byte)  ---->  [0]: ca::queryinterface

           int  ca_a;                     [1]: ca::addref

                                               [2]: ca::release

                                               [3]: ca::test_a

 

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p_b:    vp_tbl (4 byte) ----->   [0]:cb::queryinterface 

          int  cb_b;                      [1]:cb::addref

                                               [2]:cb::release

                                               [3]:cb::test_b

 

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p_bb:    vp_tbl (4 byte) -----> [0]: con:queryinterface

                                               [1]: con::addref

                                               [2]: con::release

                                               [3]: con::test_a

                                               [4]: con::qcon                    // 新添的兩個放在第一個父類的 vp_tbl 後面；

                                               [5]: con::test_con

              vp_tbl (4 byte) ----> [0]:   xxx                          // 函數同名，不使用， 可能指向 con::addref..

                                               [1]:  xxx                           // 同上

                                               [2]:  xxx

                                               [3]:con::test_b

              int   ca_a;

              int   cb_b;

              int   con_i;

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