Using nullptr in API function calls?

Question

Using C++ with Visual Studio 2010. I'm in the process of converting my NULL's to nullptr's. With my code this is fine. However if I make a call to WINAPI such as:

__checkReturn WINOLEAPI OleInitialize(IN LPVOID pvReserved);

normally I would have called this like:

::OleInitialize(NULL);

Can I safely use nullptr where I would have used NULL in a call such as this?

That is, can I do this:

::OleInitialize(nullptr);

Also same with MFC api:

CFileDialog fileDlg(TRUE, ".txt", NULL, 0, strFilter);

Can I replace

CFileDialog fileDlg(TRUE, ".txt", nullptr, 0, strFilter);

I'm guessing I can but I just want to make sure there are no gotchas.

UPDATE

So I went through and replaces all my NULL's with nullptr and it seems to work most everywhere however I am getting the below error on the following line:

propertyItem = new CMFCPropertyGridProperty(_T("SomeName"),
"SomeValue", "SomeDescription", nullptr, nullptr, nullptr, nullptr);

8>c:\something\something.cpp(118): error C2664: 'CMFCPropertyGridProperty::CMFCPropertyGridProperty(const CString &,const COleVariant &,LPCTSTR,DWORD_PTR,LPCTSTR,LPCTSTR,LPCTSTR)' : cannot convert parameter 4 from 'nullptr' to 'DWORD_PTR' 8> A native nullptr can only be converted to bool or, using reinterpret_cast, to an integral type

(Note CMFCPropertyGridProperty is a Microsoft MFC class) So what does that mean?

Community · Accepted Answer · 2017-05-23 11:59:56Z

18

Yes, you can safely use nullptr anywhere you use NULL.

NULL expanded to an integer constant expression with the value zero, which could then be converted to a null pointer value of any type. nullptr is "pointer literal" that does the exact same thing: it converts to a null pointer value of any type.

More information here.

edited May 23, 2017 at 11:59

CommunityBot

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answered Oct 29, 2011 at 22:33

GManNickG

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3 Comments

Joe McGrath Over a year ago

I'm not sure that's exactly true from reading here. If a NULL was placed somewhere it should of been 0 before than just replacing all of NULL with nullptr would break code. I see tutorials everywhere that set handles and kinds of variable types to NULL. Types that shouldn't be assigned as nullptr.

GManNickG Over a year ago

@Joe: The premise of my answer is that NULL was being used correctly, in the context of pointers.

André Caron Over a year ago

@User: this might be confusing, but DWORD_PTR is not a pointer type, but an integer. This means that, as @JoeMcGrath pointed out, you will need to use 0 in that context, not nullptr.

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