From 3a75362f0375f66ebe204c87313899ed81010731 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Thu, 17 Dec 2020 01:13:40 -0800
Subject: [PATCH 3/4] canonicalize: omit second readlink when not needed

* lib/canonicalize.c (canonicalize_filename_mode_stk):
Omit second readlink when (can_exist != CAN_MISSING
&& startlen != 0 && !logical).  Simplify.
---
 ChangeLog          |  5 +++++
 lib/canonicalize.c | 32 ++++++++------------------------
 2 files changed, 13 insertions(+), 24 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 58c7c16d7..fccedabe3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2020-12-17  Paul Eggert  <eggert@cs.ucla.edu>
 
+	canonicalize: omit second readlink when not needed
+	* lib/canonicalize.c (canonicalize_filename_mode_stk):
+	Omit second readlink when (can_exist != CAN_MISSING
+	&& startlen != 0 && !logical).  Simplify.
+
 	canonicalize: remove arbitrary 8192-byte limit
 	Remove canonicalize.c’s arbitrary 8192-byte limit on platforms
 	like GNU Hurd that do not define the PATH_MAX macro, and similarly
diff --git a/lib/canonicalize.c b/lib/canonicalize.c
index 04fae10a4..bcfd52be2 100644
--- a/lib/canonicalize.c
+++ b/lib/canonicalize.c
@@ -360,31 +360,15 @@ canonicalize_filename_mode_stk (const char *name, canonicalize_mode_t can_mode,
                     dest++;
                 }
             }
-          else if (can_exist != CAN_MISSING
-                   && (startlen == 0
-                       ? stat (rname, &st) < 0
-                       : !logical && readlink (rname, &discard, 1) < 0))
-            {
-              switch (errno)
-                {
-                case EINVAL:
-                case EOVERFLOW: /* Possible with stat.  */
-                  /* RNAME exists and is not a symbolic link.  */
-                  break;
-
-                case ENOENT:
-                  /* RNAME does not exist.  */
-                  if (can_exist == CAN_EXISTING
+          else if (! (can_exist == CAN_MISSING
+                      || (startlen == 0
+                          ? stat (rname, &st) == 0 || errno == EOVERFLOW
+                          : ((logical && 0 <= readlink (rname, &discard, 1))
+                             || errno == EINVAL))
                       || (can_exist == CAN_ALL_BUT_LAST
-                          && end[strspn (end, SLASHES)]))
-                    goto error;
-                  break;
-
-                default:
-                  /* Some other problem with RNAME.  */
-                  goto error;
-                }
-            }
+                          && errno == ENOENT
+                          && !end[strspn (end, SLASHES)])))
+            goto error;
         }
     }
   if (dest > rname + prefix_len + 1 && ISSLASH (dest[-1]))
-- 
2.27.0