error C2440: 'specialization' : cannot convert from 'int (__stdcall *)(void *)' to ' (__stdcall *)()'

template<class T, class CloseT, CloseT (_stdcall * CloseFunc)(T)> class THandle {
T m_h;
public:
THandle() {
m_h = T(-1); // Always illegal
}
THandle(T h) { m_h = h; }
~THandle() {
if (IsValid()) Close(); // Ensure we do not double-close
}
THandle<T, CloseT, CloseFunc>& operator=(T h) {
m_h = h;
return *this;
}
operator T() { return m_h; }
T *operator &() { return &m_h; }
CloseT Close() {
T h = m_h;
m_h = T(-1);
return (*CloseFunc)(h); // Return the result of whatever type
};
BOOL IsValid() { return m_h != T(-1) && m_h != T(0); }
};
//
// Now define common handles as safe classes.
//
typedef class THandle<HANDLE, BOOL, &CloseHandle> CHandle;
typedef class THandle<HKEY, LONG, &RegCloseKey> CHKey;
typedef class THandle<HANDLE, BOOL, &CloseHandle> CHFile;
typedef class THandle<HANDLE, BOOL, &FindClose> CHFind;
typedef class THandle<HANDLE, BOOL, &FindCloseChangeNotification> CHChange;
typedef class THandle<HMODULE, BOOL, &FreeLibrary> CHModule;
typedef class THandle<HWND, BOOL, &DestroyWindow> CHWnd;
//

代码见上，VC6编译的时候报
error C2440: 'specialization' : cannot convert from 'int (__stdcall *)(void *)' to ' (__stdcall *)()'
This conversion requires a reinterpret_cast, a C-style cast or function-style cast
error C2975: 'THandle' : invalid template argument for 'CloseFunc', constant expression expected see declaration of 'THandle'
.......
WHY？

13 个解决方案

#1

在线等。立即给分。

#2

error C2440: 'specialization' : cannot convert from 'int (__stdcall *)(void *)' to ' (__stdcall *)()'

传入的函数指针不匹配，如果不是错误的话，可以强制转换

return (*CloseFunc)(h);

h不是类的成员变量

#3

我在VC6 下编译没问题啊!

#4

我的QQ 361017175。在线请教。

#5

我是觉得是能够强制转换的。因为这个代码是从别人工程中拷贝的，别人能编译过。

#6

把你的变量定义贴出来看看,我这样可以编译运行
#include <windows.h>
#pragma comment (lib,"advapi32")
#pragma comment (lib,"user32")

template<class T, class CloseT, CloseT (_stdcall * CloseFunc)(T)> class THandle {
T m_h;
public:
THandle() {
m_h = T(-1); // Always illegal
}
THandle(T h) { m_h = h; }
~THandle() {
if (IsValid()) Close(); // Ensure we do not double-close
}
THandle<T, CloseT, CloseFunc>& operator=(T h) {
m_h = h;
return *this;
}
operator T() { return m_h; }
    T *operator &() { return &m_h; }
CloseT Close() {
T h = m_h;
m_h = T(-1);
return (*CloseFunc)(h); // Return the result of whatever type
};
BOOL IsValid() { return m_h != T(-1) && m_h != T(0); }
};
//
// Now define common handles as safe classes.
//
typedef class THandle<HANDLE, BOOL, &CloseHandle> CHandle;
typedef class THandle<HKEY, LONG, &RegCloseKey> CHKey;
typedef class THandle<HANDLE, BOOL, &CloseHandle> CHFile;
typedef class THandle<HANDLE, BOOL, &FindClose> CHFind;
typedef class THandle<HANDLE, BOOL, &FindCloseChangeNotification> CHChange;
typedef class THandle<HMODULE, BOOL, &FreeLibrary> CHModule;
typedef class THandle<HWND, BOOL, &DestroyWindow> CHWnd;
//

void main()
{
CHandle hd;
  hd.Close();
CHKey  ke;
  ke.Close();
CHFile fe;
  fe.Close();
CHFind fd;
  fd.Close();
CHChange ce;
   ce.Close();
CHModule me;
    me.Close();
CHWnd wd;
   wd.Close();

}

#7

我还没定义变量。单单你上面那些我就编译不过。你的VC有安装SP3吗？

#8

和VC的设置有关吗？

#9

应该与设置无关吧,我在命令行及IDE下都能通过的
我的VC已安装了sp5
装个sp5试试(microsoft网站上已有sp6了)

#10

我也是安装了SP5。
这个错误在MSDN上被视为VS的一个BUG。但是是说安装SP3就可以搞定，我都安装SP5了。

#11

你在命令行下试试(这样可排除设置问题),不行重打sp5或下个SP6(你的SP5没打好或不全?)

#12

好了，是SP5的问题。

#13

MSDN上面已经说过这个错误是VS的一个BUG，打SP3就可以。我打了SP5还是同样报错。然后下了个英文版的SP6,编译通过。估计是我下载的SP5存在问题。
谢谢keiy 。已给分。

#1