diff --git a/impl/getusername.cpp b/impl/getusername.cpp
index 839e85c47..55ca9c93c 100644
--- a/impl/getusername.cpp
+++ b/impl/getusername.cpp
@@ -12,6 +12,13 @@ const string utf8 = "UTF-8";
 // https://msdn.microsoft.com/en-us/library/windows/desktop/ms724432(v=vs.85).aspx
 // Sets errno to:
 //     ERROR_BAD_ENVIRONMENT - locale is not UTF-8
+//     ERROR_TOO_MANY_OPEN_FILES - already have the maximum allowed number of open files
+//     ERROR_NO_ASSOCIATION - calling process has no controlling terminal
+//     ERROR_INSUFFICIENT_BUFFER - buffer not large enough to hold username string
+//     ERROR_NO_SUCH_USER - there was no corresponding entry in the utmp-file
+//     ERROR_OUTOFMEMORY - insufficient memory to allocate passwd structure
+//     ERROR_NO_ASSOCIATION - standard input didn't refer to a terminal
+//     ERROR_INVALID_FUNCTION - getlogin_r() returned an unrecognized error code
 //
 // Returns:
 //     1 - succeeded
@@ -28,6 +35,46 @@ BOOL GetUserName(WCHAR_T* lpBuffer, LPDWORD lpnSize)
 		return 0;
 	}
 
+	// Get username from system in a thread-safe manner
+	char userName[*lpnSize];
+	int err = getlogin_r(userName, *lpnSize);
+	// Map errno to Win32 Error Codes
+	if (err != 0) {
+		switch (errno) {
+		case EMFILE:
+		case ENFILE:
+			errno = ERROR_TOO_MANY_OPEN_FILES;
+			break;
+		case ENXIO:
+			errno = ERROR_NO_ASSOCIATION;
+			break;
+		case ERANGE:
+			errno = ERROR_INSUFFICIENT_BUFFER;
+			break;
+		case ENOENT:
+			errno = ERROR_NO_SUCH_USER;
+			break;
+		case ENOMEM:
+			errno = ERROR_OUTOFMEMORY;
+			break;
+		case ENOTTY:
+			errno = ERROR_NO_ASSOCIATION;
+			break;
+		default:
+			errno = ERROR_INVALID_FUNCTION;
+		}
+		return 0;
+	}
+
+	// TODO: Convert to char* to wchar* (UTF-8 to UTF-16 LE w/o BOM)
+
+	// Unfortunately codecvt is not yet supported by G++, othwerise:
+	// wstring_convert<std::codecvt_utf8_utf16<char16_t>,char16_t> conversion;
+
+	// TODO: Use PAL's Unicode converters
+
+	// TODO: set the lpnSize to the userName length (see msdn)
+
 	return 1;
 }
 
diff --git a/impl/pal.h b/impl/pal.h
index 06ff5602c..f30903a2f 100644
--- a/impl/pal.h
+++ b/impl/pal.h
@@ -72,6 +72,11 @@
     #define ERROR_INVALID_PARAMETER 87
     #define ERROR_OUTOFMEMORY 14
     #define ERROR_BAD_ENVIRONMENT 0x0000000A
+    #define ERROR_TOO_MANY_OPEN_FILES 0x00000004
+    #define ERROR_INSUFFICIENT_BUFFER 0x0000007A
+    #define ERROR_NO_ASSOCIATION 0x00000483
+    #define ERROR_NO_SUCH_USER 0x00000525
+    #define ERROR_INVALID_FUNCTION 0x00000001
     #define MAX_PATH 0x00000104
     typedef unsigned long long uint64;
 #endif