X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Futimecmp.c;h=49ea5f86bae6521d620aee7215fc5b22c5e41084;hb=cd56634a4a8179fd5a4419fbb3e27211b042ab1c;hp=63a0c9a822000e0b36e92c7ab9c270f94a760b79;hpb=692679fcbebba0095bae0f1f1a99bd1f0f5a0476;p=gnulib.git

diff --git a/lib/utimecmp.c b/lib/utimecmp.c
index 63a0c9a82..49ea5f86b 100644
--- a/lib/utimecmp.c
+++ b/lib/utimecmp.c
@@ -1,6 +1,6 @@
 /* utimecmp.c -- compare file time stamps
 
-   Copyright (C) 2004-2007, 2009-2010 Free Software Foundation, Inc.
+   Copyright (C) 2004-2007, 2009-2014 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -33,7 +33,6 @@
 #include "stat-time.h"
 #include "utimens.h"
 #include "verify.h"
-#include "xalloc.h"
 
 #ifndef MAX
 # define MAX(a, b) ((a) > (b) ? (a) : (b))
@@ -122,7 +121,9 @@ utimecmp (char const *dst_name,
   /* Things to watch out for:
 
      The code uses a static hash table internally and is not safe in the
-     presence of signals, multiple threads, etc.
+     presence of signals, multiple threads, etc.  However, memory pressure
+     that prevents use of the hash table is not fatal - we just fall back
+     to redoing the computations on every call in that case.
 
      int and long int might be 32 bits.  Many of the calculations store
      numbers up to 2 billion, and multiply by 10; they have to avoid
@@ -143,12 +144,13 @@ utimecmp (char const *dst_name,
     {
       /* Look up the time stamp resolution for the destination device.  */
 
-      /* Hash table for devices.  */
+      /* Hash table for caching information learned about devices.  */
       static Hash_table *ht;
 
       /* Information about the destination file system.  */
       static struct fs_res *new_dst_res;
-      struct fs_res *dst_res;
+      struct fs_res *dst_res = NULL;
+      struct fs_res tmp_dst_res;
 
       /* Time stamp resolution in nanoseconds.  */
       int res;
@@ -163,24 +165,46 @@ utimecmp (char const *dst_name,
       if (src_s <= dst_s - 2)
         return 1;
 
+      /* Try to do a hash lookup, but fall back to stack variables and
+         recomputation on low memory situations.  */
       if (! ht)
         ht = hash_initialize (16, NULL, dev_info_hash, dev_info_compare, free);
-      if (! new_dst_res)
+      if (ht)
         {
-          new_dst_res = xmalloc (sizeof *new_dst_res);
-          new_dst_res->resolution = 2 * BILLION;
-          new_dst_res->exact = false;
-        }
-      new_dst_res->dev = dst_stat->st_dev;
-      dst_res = hash_insert (ht, new_dst_res);
-      if (! dst_res)
-        xalloc_die ();
+          if (! new_dst_res)
+            {
+              new_dst_res = malloc (sizeof *new_dst_res);
+              if (!new_dst_res)
+                goto low_memory;
+              new_dst_res->resolution = 2 * BILLION;
+              new_dst_res->exact = false;
+            }
+          new_dst_res->dev = dst_stat->st_dev;
+          dst_res = hash_insert (ht, new_dst_res);
+          if (! dst_res)
+            goto low_memory;
 
-      if (dst_res == new_dst_res)
+          if (dst_res == new_dst_res)
+            {
+              /* NEW_DST_RES is now in use in the hash table, so allocate a
+                 new entry next time.  */
+              new_dst_res = NULL;
+            }
+        }
+      else
         {
-          /* NEW_DST_RES is now in use in the hash table, so allocate a
-             new entry next time.  */
-          new_dst_res = NULL;
+        low_memory:
+          if (ht)
+            {
+              tmp_dst_res.dev = dst_stat->st_dev;
+              dst_res = hash_lookup (ht, &tmp_dst_res);
+            }
+          if (!dst_res)
+            {
+              dst_res = &tmp_dst_res;
+              dst_res->resolution = 2 * BILLION;
+              dst_res->exact = false;
+            }
         }
 
       res = dst_res->resolution;
@@ -325,7 +349,7 @@ utimecmp (char const *dst_name,
 
                 res = SYSCALL_RESOLUTION;
 
-                for (a /= res; a % 10 != 0; a /= 10)
+                for (a /= res; a % 10 == 0; a /= 10)
                   {
                     if (res == BILLION)
                       {