std::string.push_back() error in win32

Question

std::string.push_back() error in win32

Vijayadithyan .N 121

There's an error that pops up while calling std::string.push_back in Win32.
More specifically E0167: argument of type "const char *" is incompatible with parameter of type "LPCWSTR"
It works fine in regular c++ and older versions, but only in VS2022 and 2019 it shows up
here's the code:

static std::string title;
title.push_back((char)wParam);
SetWindowText(hWnd, title.c_str());

Is there any way to fix this?

Vijayadithyan .N 121 Reputation points

2022-02-24T12:49:45.323+00:00

I'm only a beginner, so please give a bit more detailed steps as to how to fix it if possible).

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Vijayadithyan .N 121 Reputation points

2022-02-24T12:49:45.323+00:00

I'm only a beginner, so please give a bit more detailed steps as to how to fix it if possible).

Answer 1

RLWA32 49,536

It is more likely that the error message relates to the call to SetWindowText. The mention of LPCWSTR (a Windows data type) indicates that this is happening in a UNICODE build where SetWindowText is resolved to SetWindowTextW for which a LPCWSTR is the second parameter. Consequently, since title.c_str() returns a const char* pointer the error is issued.

So 1)build for ascii/mbcs or 2) use std::wstring or 3) convert the std::string data to UNICODE.

Vijayadithyan .N 121 Reputation points

2022-02-24T13:18:50.647+00:00

So how exactly to you build for ascii/mbcs or convert the std::string data to unicode?
RLWA32 49,536 Reputation points

2022-02-24T13:35:54.157+00:00

For Visual Studio (I'm using VS2019) in the project properties go to Configuration Properties->Advanced->Character Set and select either "Not Set" or "Multi-Byte Character Set" from the dropdown. A setting for a Unicode build looks like this -

For example, C library function to convert ascii to unicode - mbstowcs-s-mbstowcs-s-l and Windows API function to do the same - nf-stringapiset-multibytetowidechar

Answer 2

Minxin Yu 13,501 Microsoft External Staff

Hi, @Vijayadithyan .N

You can also try to use SetWindowTextA

static std::string title;  
 title.push_back((char)wParam);  
 SetWindowTextA(hWnd, title.c_str());

Best regards,

Minxin Yu

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RLWA32 49,536 Reputation points

2022-02-25T09:42:21.357+00:00

Leaving the project character set for a Unicode build while coding exclusively for narrow strings would require that all windows API functions, structures and macros are specified with their "A" versions. For a single function call this is no big deal. However, it is inherently error-prone and compiler messages will not necessarily detect every mismatch.

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std::string.push_back() error in win32

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