From f29f9e4afc2a54e937e0403555a41734599725be Mon Sep 17 00:00:00 2001
From: "Richard M. Stallman" <rms@gnu.org>
Date: Thu, 29 Jun 1995 17:30:50 +0000
Subject: [PATCH] (child_setup): Don't get confused if in == err.

---
 src/callproc.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/src/callproc.c b/src/callproc.c
index f87223c8d44..ea995b6b09f 100644
--- a/src/callproc.c
+++ b/src/callproc.c
@@ -807,14 +807,25 @@ child_setup (in, out, err, new_argv, set_pgrp, current_dir)
      descriptors zero, one, or two; this could happen if Emacs is
      started with its standard in, out, or error closed, as might
      happen under X.  */
-  in = relocate_fd (in, 3);
-  if (out == err)
-    err = out = relocate_fd (out, 3);
-  else
-    {
+  {
+    int oin = in, oout = out;
+
+    /* We have to avoid relocating the same descriptor twice!  */
+
+    in = relocate_fd (in, 3);
+
+    if (out == oin)
+      out = in;
+    else
       out = relocate_fd (out, 3);
+
+    if (err == oin)
+      err = in;
+    else if (err == oout)
+      err = out;
+    else
       err = relocate_fd (err, 3);
-    }
+  }
 
   close (0);
   close (1);
-- 
2.39.2