canonicalize: only stat() when required

* lib/canonicalize.c (canonicalize_filename_mode):
Avoid calling l?stat() when both CAN_MISSING,
and CAN_NOLINKS are set, as then we neither need
to resolve symlinks or test component existence.

diff --git a/ChangeLog b/ChangeLog
index b380dfb..3e45b00 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2011-12-31  Pádraig Brady  <P@draigBrady.com>
+
+       canonicalize: only stat() if required
+       * lib/canonicalize.c (canonicalize_filename_mode):
+       Avoid calling l?stat() when both CAN_MISSING,
+       and CAN_NOLINKS are set, as we neither need
+       to resolve symlinks or test component existence.
+
 2011-12-31  Paul Eggert  <eggert@cs.ucla.edu>
 
        doc: cover st_ino issues once; add OpenVMS etc.

diff --git a/lib/canonicalize.c b/lib/canonicalize.c
index e84c339..e5b69d9 100644 (file)
--- a/lib/canonicalize.c
+++ b/lib/canonicalize.c
@@ -198,7 +198,14 @@ canonicalize_filename_mode (const char *name, canonicalize_mode_t can_mode)
           dest += end - start;
           *dest = '\0';
 
-          if ((logical ? stat (rname, &st) : lstat (rname, &st)) != 0)
+          if (logical && (can_mode == CAN_MISSING))
+            {
+              /* Avoid the stat in this case as it's inconsequential.
+                 i.e. we're neither resolving symlinks or testing
+                 component existence.  */
+              st.st_mode = 0;
+            }
+          else if ((logical ? stat (rname, &st) : lstat (rname, &st)) != 0)
             {
               saved_errno = errno;
               if (can_mode == CAN_EXISTING)