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

[Peter Klausler via cfe-commits]

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@@ -10,10 +10,52 @@
 // extensions that will eventually be implemented in Fortran.
 
 #include "flang/Runtime/extensions.h"
+#include "terminator.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
+#define LOGIN_NAME_MAX UNLEN
+
+inline int getlogin_r(char *buf, size_t bufSize) {
+  wchar_t w_username[UNLEN + 1];
+  DWORD nameLen{UNLEN + 1};
+
+  if (GetUserName(w_username, &nameLen)) {
+    // Convert the wchar_t string to a regular C string using wcstombs_s
+    if (wcstombs_s(nullptr, buf, bufSize, w_username, _TRUNCATE) != 0) {
+      // Conversion failed
+      return -1;
+    }
+    return (buf[0] == 0 ? -1 : 0);
+  } else {
+    return -1;
+  }
+  return -1;
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klausler wrote:

This line will never be reached.

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