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copied!<p>As others have pointed out in the comments, the Windows APIs do not provide direct support for UTF-8 encoded text. You cannot pass the <code>MessageBox</code> function UTF-8 encoded strings and get the output that you expect. It will, instead, interpret them as characters in your local code page.</p> <p>To get a UTF-8 string to pass to the Windows API functions (including <code>MessageBox</code>), you need to use the <a href="http://msdn.microsoft.com/en-us/library/windows/desktop/dd319072.aspx" rel="nofollow noreferrer"><code>MultiByteToWideChar</code></a> function to convert from UTF-8 to UTF-16 (what Windows calls Unicode, or wide strings). Passing the <code>CP_UTF8</code> flag for the first parameter is the magic that enables this conversion. Example:</p> <pre><code>std::wstring ConvertUTF8ToUTF16String(const char* pszUtf8String) { // Determine the size required for the destination buffer. const int length = MultiByteToWideChar(CP_UTF8, 0, // no flags required pszUtf8String, -1, // automatically determine length nullptr, 0); // Allocate a buffer of the appropriate length. std::wstring utf16String(length, L'\0'); // Call the function again to do the conversion. if (!MultiByteToWideChar(CP_UTF8, 0, pszUtf8String, -1, &utf16String[0], length)) { // Uh-oh! Something went wrong. // Handle the failure condition, perhaps by throwing an exception. // Call the GetLastError() function for additional error information. throw std::runtime_error("The MultiByteToWideChar function failed"); } // Return the converted UTF-16 string. return utf16String; } </code></pre> <p>Then, once you have a wide string, you will explicitly call the wide-string variant of the <code>MessageBox</code> function, <code>MessageBoxW</code>.</p> <p>However, if you only need to support Windows and not other platforms that use UTF-8 everywhere, you will probably have a much easier time sticking exclusively with UTF-16 encoded strings. This is the native Unicode encoding that Windows uses, and you can pass these types of strings directly to any of the Windows API functions. See <a href="https://stackoverflow.com/questions/15458312/how-do-i-properly-call-the-copyfile-function-in-visual-c/15458564#15458564">my answer here</a> to learn more about the interaction between Windows API functions and strings. I recommend the same thing to you as I did to the other guy:</p> <ul> <li>Stick with <code>wchar_t</code> and <code>std::wstring</code> for your characters and strings, respectively. </li> <li>Always call the <code>W</code> variants of Windows API functions, including <code>LoadStringW</code> and <code>MessageBoxW</code>.</li> <li>Ensure that the <code>UNICODE</code> and <code>_UNICODE</code> macros are defined either before you include any of the Windows headers or in your project's build settings.</li> </ul>

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