CString -- ATL::CStringT<char, StrTraitMFCDLL format problem

Question

CString -- ATL::CStringT<char, StrTraitMFCDLL format problem

Noah Aas 685

Hello, I got this warning. https://learn.microsoft.com/en-us/cpp/code-quality/c6284?view=msvc-160

CString Logging::AddEntry(CString strEntry)
{
	SYSTEMTIME stTimestamp;
	CString    strNewEntry = _T("");
	CString    strTempEntry = strEntry;
	CString    strTempOldFile = _T("");
	if (m_bWithTimestamp)
	{
		GetLocalTime(&stTimestamp);
		strNewEntry.Format(_T("[%02d:%02d:%02d.%003d] %s\r\n"), stTimestamp.wHour, stTimestamp.wMinute, stTimestamp.wSecond, stTimestamp.wMilliseconds, strTempEntry);
	}
	// Neuer Eintrag ohne Zeitstempel
	else
	{
		strNewEntry.Format(_T("%s\r\n"), strTempEntry);
	}

enter image description here

How can I solve it? What is wrong? I need only CString and ANSII coding. No unicode.

framework.h    stdafx.h
#define _ATL_CSTRING_EXPLICIT_CONSTRUCTORS
#define _AFX_ALL_WARNINGS

#include <afxstr.h>
#include <atlbase.h>
#include <string>

#include <afxwin.h>
#include <afxext.h>
#include <afxdisp.h>
#ifndef _AFX_NO_OLE_SUPPORT
#include <afxdtctl.h>
#endif
#ifndef _AFX_NO_AFXCMN_SUPPORT
#include <afxcmn.h>
#endif
#include <afxcontrolbars.h>
#include <afxsock.h>
//https://github.com/microsoft/VCSamples/blob/master/VC2010Samples/MFC/Visual%20C%2B%2B%202008%20Feature%20Pack/OutlookDemo/stdafx.h

Thanks in advance.

1 answer

Your answer

Answer 1

RLWA32 47,526

In the call to CString::Format pass (LPCTSTR) strTempEntry. This will satisfy the compiler that is looking for a char* pointer not a CString object

Noah Aas 685 Reputation points

2025-03-11T16:02:20.18+00:00
strNewEntry.Format(_T("%s\r\n"), strTempEntry);

Can you please write the line correctly as you mean it? It's all CString.
RLWA32 47,526 Reputation points

2025-03-11T16:30:55.7666667+00:00
I meant -

strNewEntry.Format(_T("%s\r\n"), (LPCTSTR) strTempEntry);
Noah Aas 685 Reputation points

2025-03-12T07:15:31.41+00:00
Yes works well.

strNewEntry.Format(_T("%s\r\n"), (LPCTSTR) strTempEntry); strNewEntry.Format("%s\r\n", strTempEntry);

So _T was the reason, isn't it?

The old code use s lot of variables with CString.

Is there a way, adjustment to go faster?

Is only a warning, maybe I can switch off.
RLWA32 47,526 Reputation points

2025-03-12T07:58:12.9066667+00:00
So _T was the reason, isn't it?

No, it wasn't. Wrapping string literals with _T or TEXT is done if the intent is to write code that can successfully be compiled as unicode or non-unicode. For the same reason CString resolves to either CStringA or CStringW depending on the project character set.

The warning message was generated because when the compiler sees %s in a format specification it expects the related parameter to be a pointer to a null-terminated string. And depending on the character set chosen that would be either char* or wchar_t* and (LPCTSTR) also takes into account the chosen character set.

Although I don't recommend turning off warnings it can be disabled with

#pragma warning(disable: 6284)

Refer to warning pragma
Noah Aas 685 Reputation points

2025-03-12T09:17:32.7033333+00:00
For the same reason CString resolves to either CStringA or CStringW depending on the project character set.

OK, how would you solve this? How Do I switch?

Unicode

Ansii

Yes not a good way to switch off warnings

In program settings? Multibyte character

So the warning is not bad. I can ignore them, but display them?

Right?
RLWA32 47,526 Reputation points

2025-03-12T09:28:12.5266667+00:00

OK, how would you solve this? How Do I switch?

As I said earlier, the project properties character set controls this.

I think I've answered your question about the C6284 warning and how to avoid it.

It's not clear to me what other problem you think needs a solution.

Share via

CString -- ATL::CStringT<char, StrTraitMFCDLL format problem

1 answer

Your answer