- FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER|FORMAT_MESSAGE_FROM_SYSTEM,
- NULL, GetLastError(), 0, (LPSTR)&buffer, 1, NULL);
- *ErrMsg = prefix + buffer;
+ DWORD R = FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER |
+ FORMAT_MESSAGE_FROM_SYSTEM,
+ NULL, GetLastError(), 0, (LPSTR)&buffer, 1, NULL);
+ if (R)
+ *ErrMsg = prefix + buffer;
+ else
+ *ErrMsg = prefix + "Unknown error";
+