[flang] [clang] [clang-tools-extra] [llvm] [flang ]GETLOG runtime and extension implementation: get login username (PR #70917)

[Yi Wu via llvm-commits]

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@@ -13,6 +13,44 @@
 #include "flang/Runtime/command.h"
 #include "flang/Runtime/descriptor.h"
 #include "flang/Runtime/io-api.h"
+#include <string.h>
+
+#ifdef _WIN32
+#define WIN32_LEAN_AND_MEAN
+#define NOMINMAX
+#include <windows.h>
+
+#include <lmcons.h> // UNLEN=256
+#include <stdlib.h> // wcstombs_s
+#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 (GetUserNameW(w_username, &nameLen)) {
+    // Convert the wchar_t string to a regular C string using wcstombs_s
+    if (wcstombs_s(nullptr, buf, sizeof(w_username), w_username, _TRUNCATE) !=
+        0) {
+      // Conversion failed
+      return -1;
+    }
+    return (buf[0] == 0 ? -1 : 0);
+  } else {
+    return -1;
+  }
+  return -1;
+}
+
+#elif _REENTRANT || _POSIX_C_SOURCE >= 199506L
+// System is posix-compliant and has getlogin_r
+#include <unistd.h>
+#else
+// System is not posix-compliant
+inline int getlogin_r(char *buf, size_t bufsize) { return -1; }
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PAX-12-WU wrote:

Good suggestion!

https://github.com/llvm/llvm-project/pull/70917