[flang] [llvm] [flang] Add HOSTNM runtime and lowering intrinsics implementation (PR #131910)

[Eugene Epshteyn via llvm-commits]

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@@ -263,4 +263,48 @@ std::int32_t RTNAME(GetCwd)(
   return status;
 }
 
+std::int32_t RTNAME(Hostnm)(
+    const Descriptor &res, const char *sourceFile, int line) {
+  Terminator terminator{sourceFile, line};
+
+  RUNTIME_CHECK(terminator, IsValidCharDescriptor(&res));
+
+  char buf[256];
+  std::int32_t status{0};
+
+  // Fill the output with spaces. Upon success, CopyCharsToDescriptor()
+  // will overwrite part of the string with the result, so we'll end up
+  // with a padded string. If we fail to obtain the host name, we return
+  // the string of all spaces, which is the original gfortran behavior.
+  FillWithSpaces(res);
+
+#ifdef _WIN32
+
+  DWORD dwSize{sizeof(buf)};
+
+  // Note: Winsock has gethostname(), but use Win32 API GetComputerNameEx(),
+  // in order to avoid adding dependency on Winsock.
+  if (!GetComputerNameEx(ComputerNameDnsHostname, buf, &dwSize)) {
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eugeneepshteyn wrote:

Yeah, meant to use `GetComputerNameExA`. Somehow the Windows check didn't run when I first uploaded this PR.

https://github.com/llvm/llvm-project/pull/131910