[英]C++ function pointer type is not compatible with candidate on Linux and VMS
This question is related to my another question- boost::bind return a function object which is the argument for a function that requires pointer 这个问题与我的另一个问题有关-boost :: bind返回一个函数对象,该对象是需要指针的函数的参数
Except the interface of 除了接口
bridge_set_pound_var_func
is not allowed to be changed. 不允许更改。
Also, boost::function
or boost::bind
do not work well with the large project. 另外, boost::function
或boost::bind
在大型项目中不能很好地工作。
My new code is as follows: 我的新代码如下:
#include <iostream>
class myA
{
public:
int bridge_set_pound_var_func(int (*fp)(const char *, char *, void *), void *arg)
{
void * b = NULL;
int a = fp("this is poundVar", "ths is t1", b) ;
std::cout << "bridge_set_pound_var_func is called "<< " , a is " << a << std::endl ;
return 0;
}
};
class myC
{
public:
myA *myOA;
int func(const char * poundVar , char * t1, void * t2);
int myCCall()
{
myA myAO;
myOA = &myAO;
std::cout << "myCCall is called " << std::endl;
myOA->bridge_set_pound_var_func( &myC::func, (void *)this );
return 0;
}
};
int myC::func(const char * poundVar , char * t1, void * t2)
{
std::cout << "myC::func is called " << std::endl;
return 1;
}
int main()
{
myC myCO ;
myC *m1p = &myCO ;
m1p->myCCall() ;
return 0 ;
}
// EOF
The errors on Linux : Linux上的错误:
In member function 'int myC::myCCall()':
error: no matching function for call to 'myA::bridge_set_pound_var_func(int (myC::*)(const char*, char*, void*), void*)'
candidates are: int myA::bridge_set_pound_var_func(int (*)(const char*, char*, void*), void*)
errors on VMS: VMS上的错误:
In member function 'int myC::myCCall()':
error: no matching function for call to 'myA::bridge_set_pound_var_func(int (myC::*)(const char*, char*, void*), void*)'
candidates are: int myA::bridge_set_pound_var_func(int (*)(const char*, char*, void*), void*)
The short answer is: pointers to member functions are not pointer to functions. 简短的答案是:指向成员函数的指针不是指向函数的指针。 The former need to know about the object they are called on, the latter don't. 前者需要知道它们被调用的对象,后者则不需要。 A typical approach used is to use the usually present "user data" void*
to point to a suitable base class, cast the pointer and call a corresponding virtual function. 使用的一种典型方法是使用通常存在的“用户数据” void*
指向合适的基类,强制转换指针并调用相应的虚函数。 Frim there you can recover the necessary object context easily. 在那里,您可以轻松地恢复必要的对象上下文。
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