error C2440: 'static_cast' : cannot convert from 'int (__thiscall CINVOICEView::* )(v

Hi
I am trying to port old version C++ code into Visual Studio 2013. When I am trying to do this, I am getting the following error.

1> INVOICEView.cpp
1>INVOICEView.cpp(23): error C2440: 'static_cast' : cannot convert from 'int (__thiscall CINVOICEView::* )(void)' to 'AFX_PMSG'
1> None of the functions with this name in scope match the target type
1>INVOICEView.cpp(23): fatal error C1903: unable to recover from previous error(s); stopping compilation
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Here is the code....

ON_COMMAND(ID_SAVE_TO_HOST, OnSaveToHost)


#define ON_COMMAND(id, memberFxn) \
{ WM_COMMAND, CN_COMMAND, (WORD)id, (WORD)id, AfxSigCmd_v, \
static_cast<AFX_PMSG> (memberFxn) },
// ON_COMMAND(id, OnBar) is the same as
// ON_CONTROL(0, id, OnBar) or ON_BN_CLICKED(0, id, OnBar)



int CINVOICEView::OnSaveToHost()
{
return (SaveToHost());
}


Any help to fix the above error would be appreciated. Please do let me know if you need any additional details. Thank you.

Quote:

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Originally Posted by svsrkm

Here is the code....

ON_COMMAND(ID_SAVE_TO_HOST, OnSaveToHost)


#define ON_COMMAND(id, memberFxn) \
{ WM_COMMAND, CN_COMMAND, (WORD)id, (WORD)id, AfxSigCmd_v, \
static_cast<AFX_PMSG> (memberFxn) },
...

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Why do you redefine the ON_COMMAND macro already defined by the framework?

I guess, it's a copy paste from VC++'s standard headers ;-)

Quote:

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Originally Posted by AvDav

I guess, it's a copy paste from VC++'s standard headers ;-)

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Good point!
Anyway, dear svsrkm, will you be so kind to post the declaration of your OnSaveToHost message handler?

Quote:

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Originally Posted by svsrkm

[...]

ON_COMMAND(ID_SAVE_TO_HOST, OnSaveToHost)


#define ON_COMMAND(id, memberFxn) \
{ WM_COMMAND, CN_COMMAND, (WORD)id, (WORD)id, AfxSigCmd_v, \
static_cast<AFX_PMSG> (memberFxn) },
// ON_COMMAND(id, OnBar) is the same as
// ON_CONTROL(0, id, OnBar) or ON_BN_CLICKED(0, id, OnBar)



int CINVOICEView::OnSaveToHost()
{
return (SaveToHost());
}

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When map a message by hand (not using the good wizard), MUST repect the required signature for the message handler!
If you go to AFX_PMSG macro definition you'll see:

Code:

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typedef void (AFX_MSG_CALL CCmdTarget::*AFX_PMSG)(void);

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This is a pointer to a member function that has no parameters and returns void type. Your handler function returns int. For that reason there is not possible to convert using static_cast.
In older MFC versions, it was there a C-style cast, so compiler didn't coplain. That's very bad! The use of handlers with incorrect signature was a common generator of insidious bugs, many of them leading to application crashes randomly and only in the release builds.

So, if summarize the solution for this particular issue, you need to either redefine a message handler macro as mentioned to set as:

Code:

---

typedef int (AFX_MSG_CALL CCmdTarget::*MYAFX_MSG)(void)

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Or consider to change your handler's returning type to void.
I guess there are several other ways to check the correctness of the function call except for returning an integer value.
Especially, from what I have guessed from the name of the function, the project is related to socket programming, and there are error handling routines available when dealing with WinSock systems' call (e.g.: WSAGetLastError()).

Quote:

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I am trying to port old version C++ code into Visual Studio 2013

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Why are trying to port 'old version code' to a 4-year old compiler? Why not port to the current version VS2017?

Quote:

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Originally Posted by 2kaud

Why are trying to port 'old version code' to a 4-year old compiler? Why not port to the current version VS2017?

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I assume, this would cost big money. God bless Armenian internet, I can easily violate intellectual property rights from here. ;-)

Quote:

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Originally Posted by AvDav

[...] you need to either redefine a message handler macro as mentioned to set as:

Code:

---

typedef int (AFX_MSG_CALL CCmdTarget::*MYAFX_MSG)(void)

---

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Bad idea!
Returning an error code from VM_COMMAND message handler has NOT any sense. Just have a look in the MSDN documentation.
The second choice is the right one:

Quote:

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Originally Posted by AvDav

Or consider to change your handler's returning type to void.
I guess there are several other ways to check the correctness of the function call [...]

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