Cannot convert argument 1 from 'const char [5]' to 'LPCTSTR'

Question

I'm using this codeproject: http://www.codeproject.com/Articles/10138/Voice-Recording-Playing-back-using-simple-classes

void CFisterDlg::OnRecord() 
{
    CString string;
    m_RecButton.GetWindowText(string);
    if(string == "Record")
    {
        StartRecordingToFile();
        m_RecButton.SetWindowText("Stop");
    }
    else
    {
        StopRecordingToFile();
        m_RecButton.SetWindowText("Record");
    }
}

But I get this error in numerous places:

error C2664: 'void CWnd::SetWindowTextW(LPCTSTR)' : cannot convert argument 1 from 'const char [5]' to 'LPCTSTR'

I think it has something to do with me using the latest version of visual studio (2013).

@cybermonkey It's StackOverflow, not Grand Theft Auto: there's no steal. — edmz, Apr 22 '15 at 14:27
@cybermonkey See [similar](http://stackoverflow.com/questions/14370982/converting-const-char-to-lpctstr-for-createdirectory) question. Has the same solution that i posted, yet i received 3 downvotes. Got to love stackoverflow. — Javia1492, Apr 22 '15 at 14:35
You have accepted a *very* damaging answer. Please consider changing it. — AStopher, Apr 22 '15 at 20:01
@Yakk Look at Remy's third paragraph/code block. That will clarify the reason. — Javia1492, Apr 22 '15 at 20:51

score 5 · Answer 1 · answered Apr 22 '15 at 19:57

There are two kinds of raw strings that MSVC2013 interacts with. Raw char strings look like "Hello". wchar_t strings look like L"World".

In addition, there is a setting for if your project is using wchar_t or char strings. The macro TCHAR expands to either char or wchar_t, and the macro _T("some text") will expand to either "some text" or L"some text" depending on if your project is compiled to use char or wchar_t.

Almost every windows API taking a string has a macro wrapping it, mapping it to a char version or a wchar_t version.

The goal of all of this was to make it possible to write a single application, and have it wide-character aware or not.

The convention on windows is that narrow character char interfaces use a code-page based system, and wide character wchar_t interfaces use UTF-16 characters (the subset UCS-2 in OS's prior to W2K, and no system font in XP supports characters outside of UCS-2 if I read the wikipedia article right).

The end of all of this? Your project has been somehow set to be using wide character strings. This is a good thing, because narrow character built apps are unable to handle anything other than one codepage of characters.

So your narrow character constants are generating errors, as the APIs are now expecting wide character constants.

The easy fix is to wrap all of your "raw strings"s in _T("raw string") the _T macro. When you use char const* or the like in your code, instead use TCHAR const*.

Include a system to do the same with std::string and std::cout and other char based std and other libraries, or when using those don't interact with the user and when talking to windows use the A terminated interfaces for char or W terminated interface functions for wchar_t based strings.

It is rare nowadays to ever "go back" to char based interfaces on windows, so one approach would be to do away with the macros and just interact with the W based interfaces directly. Your strings all become L"wide character", your std stuff is all std::wstring etc, and your character variables are all wchar_t. This is probably not considered best practices.

Finally, note that both the char and wchar_t narrow and wide based interfaces can have more than one char or wchar_t per "character". This wasn't true for a narrow window when all windows supported was single-wchar_t elements from UTF-16, and multi-wchar_t characters are relatively rare, so a lot of code fails to handle that possibility.

Your explanation is very informative, but your solution is no more different than mine. OP's question is very simple and focused, whereas your answer delves into the history and roots of microsoft's thinking. At the end of the day, both `_T()` and `L""` fix OP's solution, which is that he needs. Conversion of regular char to wchar_t. I dont see how this is any different that my "damaging" answer. — Javia1492, Apr 22 '15 at 21:00

AStopher · Answer 2 · 2016-07-03T13:00:26.463

To convert a const char * to an LPCTSTR type, add L before the const char *, as per se:

void CFisterDlg::OnRecord() 
{
    CString string;
    m_RecButton.GetWindowText(string);
    if(string == "Record")
    {
        StartRecordingToFile();
        m_RecButton.SetWindowText(L"Stop");
    }
    else
    {
        StopRecordingToFile();
        m_RecButton.SetWindowText(L"Record");
    }
}

Alternatively you could inexplicably cast it with _T, like so:

void CFisterDlg::OnRecord() 
{
    CString string;
    m_RecButton.GetWindowText(string);
    if(string == "Record")
    {
        StartRecordingToFile();
        m_RecButton.SetWindowText(_T("Stop"));
    }
    else
    {
        StopRecordingToFile();
        m_RecButton.SetWindowText(_T("Record"));
    }
}

The _T macro comes from the 'tchar' library, therefore you'll need to #include <tchar.h> if you haven't already done so.

Javia1492 · Accepted Answer · 2015-04-22T21:05:12.997

2

SetWindowTextW() takes a character pointer to the string's data where your string data consists of regular chars, but your function most likely expects a unicode string, so you cannot input string types directly. You need to use L"thisismystring"

edited Apr 22 '15 at 21:05

answered Apr 22 '15 at 14:22

Javia1492

862
11
28

Can you elaborate on its degree of wrongness? What specifically is incorrect? – Javia1492 Apr 22 '15 at 20:45
@Yakk That's interesting because i've received this error multiple times in my work and have solved it using the solution i've provided. Maybe it is platform specific, mine being Wec7 RTOS. Nevertheless, i've provided a solution that i have used myself and have seen in other works. Likewise, you can reference [this](https://msdn.microsoft.com/en-us/library/windows/desktop/ms633546(v=vs.85).aspx) which goes into detail about the `SetWindowText` function and you can read about the specifics of the parameter. **I am using VS2008 and have received this error. It is not related to VS version**. – Javia1492 Apr 22 '15 at 20:50
@Yakk What i meant to say is **a character pointer to the string's data.** I'' revise my grammar. – Javia1492 Apr 22 '15 at 21:04
2

The second edit repaired the answer. It still confuses `unicode* with *wide-character*, but that confusion is nearly mandated on windows. -1 removed, +1 added. – Yakk - Adam Nevraumont Apr 22 '15 at 21:08
The answer itself isn't wrong, the explanation however was (*and still is*). – AStopher Apr 23 '15 at 07:40
@cybermonkey can you explain how it is still wrong? – Javia1492 Apr 23 '15 at 13:01
@Javia1492 As Yakk says, your answer confuses a `unicode` with a wide character. – AStopher Apr 26 '15 at 09:03

Mekap · Answer 4 · 2015-04-22T14:31:21.930

0

LPCTSTR is a cstring operator. I advocate you to do this in all your calls to setWindowTExt

setWindowText(_T("Record"))

_T() will call the implicit cast directly if the function is known from the compiler (Which is the case here). You could use L"" aswell, thanks to @Mgetzfor point it out.

edited Apr 22 '15 at 14:31

answered Apr 22 '15 at 14:25

Mekap

2,065
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nobody is using windows 9x anymore, there is no need to use `_T()` any more, just use `L""` – Mgetz Apr 22 '15 at 14:28
@Mgetz In France there's still waaay more windows 9X that'd you think ! That's why i prefer to point out _T() anyway. But yeah, i should have putted both styles. – Mekap Apr 22 '15 at 14:30
Using `_T` is good for compatibility, although it's surpassed by the newer `L`. – AStopher Apr 22 '15 at 14:32
In which way its surpassed in terms of compatibility @cybermonkey ? – Mekap Apr 22 '15 at 14:33

score 0 · Answer 5 · answered Apr 01 '17 at 01:50

Try using Mulit-byte character encoding in Project Settings instead of Unicode. In case of VS2013, VS2015 you need to download and install the MBCS library for visual studio from this link https://www.microsoft.com/en-us/download/confirmation.aspx?id=40770

score -4 · Answer 6 · edited Apr 22 '15 at 19:38

-4

Try something like this:

char ch[5] = "test";
int num = MultiByteToWideChar(0,0,ch,-1,NULL,0); 
wchar_t *wide = new wchar_t[num];
MultiByteToWideChar(0,0,ch,-1,wide,num);

edited Apr 22 '15 at 19:38

kguest

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answered Apr 22 '15 at 14:26

wshcdr

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Cannot convert argument 1 from 'const char [5]' to 'LPCTSTR'

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