【求解】未定义的析构函数

abc说明：定义 del 函数的时候，abc 的析构函数未定义，因此不会调用。看如下代码，试解释器运行结果

#include <stdio.h>
class abc;
void del(abc *pobj)
{ 
    delete pobj;

}
class abc{
public: 
    abc()
    {
     printf("abc\r\n"); 
     } 
     ~abc()
     {
     printf("~abc\r\n"); 
     }
 };
 int main(int argc, char *argv[])
 { 
    abc *pobj = new abc; 
    del(pobj);
    return 0;
 }
 

　编译出现警告

C:\Users\Ares\Desktop>g++ test.cpp
test.cpp: In function `void del(abc*)':
test.cpp:5: warning: possible problem detected in invocation of delete operator:
test.cpp:4: warning: `pobj' has incomplete type
test.cpp:2: warning: forward declaration of `struct abc'
test.cpp:5: note: neither the destructor nor the class-specific operator delete
will be called, even if they are declared when the class is defined.
test.cpp:27:2: warning: no newline at end of file

　　abc

说明：定义 del 函数的时候，abc 的析构函数未定义，因此不会调用。感觉有说服力么？