C++在類之間調用static_cast轉換時，需要複製建構函式

下面代碼因為T2沒有實現T2(T1)複製建構函式，所以編譯錯誤

g++報錯：test.cpp|23 col 25| 錯誤： 對‘T2::T2(T1&)’的調用沒有匹配的函數

 

#include <vector>#include<stdio.h>#include <string.h>#include<iostream>#include <string>using namespace std;class T1{public:int a;double b;};class T2{public:int a;double b;};int main(){T1 t1;t1.a = 2, t1.b = 1.5;T2 t2 = static_cast<T2>(t1);return 0;}

類之間不能用reinterpret_cast轉換，儘管定義了T2(T1&)也出錯：

 

G++報錯：test.cpp|27 col 33| 錯誤： 從類型‘T1’到類型‘T2’的轉換無效

 

#include <vector>#include<stdio.h>#include <string.h>#include<iostream>#include <string>using namespace std;class T1{public:int a;double b;};class T2{public:T2(T1& t1){a = t1.a;b = t1.b;}int a;double b;};int main(){T1 t1;t1.a = 2, t1.b = 1.5;T2 t2 = reinterpret_cast<T2>(t1);return 0;}