From e03c638d0d0bd2ab50940bc479cb5b7ff18c9803 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Thu, 9 May 2024 14:10:20 +0200
Subject: Fix fdterm() mis-classification of nul on Windows with
 GetConsoleMode() call

---
 libbutl/fdstream.cxx | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/libbutl/fdstream.cxx b/libbutl/fdstream.cxx
index 07cb9f2..df5b531 100644
--- a/libbutl/fdstream.cxx
+++ b/libbutl/fdstream.cxx
@@ -1889,7 +1889,13 @@ namespace butl
       throw_system_ios_failure (e);
 
     if (t == FILE_TYPE_CHAR) // Terminal.
-      return true;
+    {
+      // One notable special file that has this type is nul (as returned by
+      // fdopen_null()). So tighten this case with the GetConsoleMode() call.
+      //
+      DWORD m;
+      return GetConsoleMode (h, &m) != 0;
+    }
 
     if (t != FILE_TYPE_PIPE) // Pipe still can be a terminal (see below).
       return false;
-- 
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