1  #pragma once
 2  
 3  #define WIN32_LEAN_AND_MEAN
 4  #include <Windows.h>
 5  
 6  #include <optional>
 7  #include <string>
 8  #include <system_error>
 9  #include <strsafe.h>
10  
11  inline std::optional<std::wstring> get_last_error_message(const DWORD dw)
12  {
13      std::optional<std::wstring> message;
14      try
15      {
16          const auto msg = std::system_category().message(dw);
17          message.emplace(begin(msg), end(msg));
18      }
19      catch (...)
20      {
21      }
22      return message;
23  }
24  
25  inline std::wstring get_last_error_or_default(const DWORD dw)
26  {
27      auto message = get_last_error_message(dw);
28      return message.has_value() ? *message : L"";
29  }
30  
31  inline void show_last_error_message(const wchar_t* functionName, DWORD dw, const wchar_t* errorTitle)
32  {
33      const auto system_message = get_last_error_message(dw);
34      if (!system_message.has_value())
35      {
36          return;
37      }
38      LPWSTR lpDisplayBuf = static_cast<LPWSTR>(LocalAlloc(LMEM_ZEROINIT, (system_message->size() + lstrlenW(functionName) + 40) * sizeof(WCHAR)));
39      if (lpDisplayBuf != NULL)
40      {
41          StringCchPrintfW(lpDisplayBuf,
42                           LocalSize(lpDisplayBuf) / sizeof(WCHAR),
43                           L"%s: %s (%d)",
44                           functionName,
45                           system_message->c_str(),
46                           dw);
47          MessageBoxW(NULL, lpDisplayBuf, errorTitle, MB_OK | MB_ICONERROR);
48          LocalFree(lpDisplayBuf);
49      }
50  }