warning C4355: “this”: 用于基成员初始值设定项列表

[春天到了冬天还远吗]

我在想，为什么会出现这个警告，各位达人指点一下

class B;
class A
{
	B* m_pB;
public:
	A(B* pB)
	{
		m_pB = pB;	
	}
};
class B
{
	A a;
public:
	B() : a(this)
	{

	}
};


int _tmain(int argc, _TCHAR* argv[])
{
	B a;
	return 0;
}

[春天到了冬天还远吗]

[Quote=引用 3 楼 dizuo 的回复:]
错误提示已经很明显了么。B的构造函数中使用this指针。
http://cboard.cprogramming.com/cplusplus-programming/99530-warning-c4355-used-base-member-initializer-list.html
[/Quote]
看到了呀，我想问，构造函数中为什么不能用this指针，不过你给的地址可能有说明，我去研究研究

[春天到了冬天还远吗]

用 dev cpp试了下，没这个警告

[ryfdizuo]

错误提示已经很明显了么。B的构造函数中使用this指针。
http://cboard.cprogramming.com/cplusplus-programming/99530-warning-c4355-used-base-member-initializer-list.html

[ouyh12345]

参数应该是某个类型吧

[luciferisnotsatan]

Error Message
'this' : used in base member initializer list


The this pointer is valid only within nonstatic member functions. It cannot be used in the initializer list for a base class.

The base-class constructors and class member constructors are called before this constructor. In effect, you've passed a pointer to an unconstructed object to another constructor. If those other constructors access any members or call member functions on this, the result will be undefined. You should not use the this pointer until all construction has completed.

This is a level-1 warning under Microsoft extensions (/Ze) and a level-4 warning otherwise.

The following sample generates C4355:

Copy Code

// C4355.cpp
// compile with: /W1 /c
#include <tchar.h>

class CDerived;
class CBase {
public:
   CBase(CDerived *derived): m_pDerived(derived) {};
   ~CBase();
   virtual void function() = 0;

   CDerived * m_pDerived;
};

class CDerived : public CBase {
public:
   CDerived() : CBase(this) {};   // C4355 "this" used in derived c'tor
   virtual void function() {};
};

CBase::~CBase() {
   m_pDerived -> function();
}

int main() {
   CDerived myDerived;
}
 

[AI1982]

构造a时b还没有构造完毕，编译器不能探测a构造的实现细节，所以给出的只是警告。要想消除警告，就得把a放在花括号里构造。