[llvm] [flang] [clang-tools-extra] [clang] [flang] GETLOG runtime and extension implementation: get login username (PR #74628)

[Yi Wu via cfe-commits]

================
@@ -10,10 +10,50 @@
 // extensions that will eventually be implemented in Fortran.
 
 #include "flang/Runtime/extensions.h"
+#include "flang/Runtime/character.h"
 #include "flang/Runtime/command.h"
 #include "flang/Runtime/descriptor.h"
 #include "flang/Runtime/io-api.h"
 
+#ifdef _WIN32
+#define WIN32_LEAN_AND_MEAN
+#define NOMINMAX
+#include <windows.h>
+
+#include <cstdlib> // wcstombs_s
+#include <lmcons.h> // UNLEN=256
+#include <wchar.h> // wchar_t cast to LPWSTR
+#pragma comment(lib, "Advapi32.lib") // Link Advapi32.lib for GetUserName
----------------
yi-wu-arm wrote:

avoidable, Windows environment variable for username is `USERNAME`.

https://github.com/llvm/llvm-project/pull/74628