(hash_string_insert_prefix): New function

(hash_string_insert): Rewrite using hash_string_insert_prefix
(safer_name_suffix): Use hash_string_insert_prefix to avoid
stack allocation. Bug reported by Dmitry V. Levin

1 files changed, 35 insertions, 12 deletions

diff --git a/paxlib/names.c b/paxlib/names.c
index 97d0a95..7e84cec 100644
--- a/paxlib/names.c
+++ b/paxlib/names.c
@@ -36,15 +36,27 @@ hash_string_compare (void const *name1, void const *name2)
   return strcmp (name1, name2) == 0;
 }
 
-/* Return zero if TABLE contains a copy of STRING; otherwise, insert a
-   copy of STRING to TABLE and return 1.  */
-bool
-hash_string_insert (Hash_table **table, char const *string)
+/* Return zero if TABLE contains a LEN-character long prefix of STRING,
+   otherwise, insert a newly allocated copy of this prefix to TABLE and
+   return 1.  If RETURN_PREFIX is not NULL, point it to the allocated
+   copy. */
+static bool
+hash_string_insert_prefix (Hash_table **table, char const *string, size_t len,
+			   const char **return_prefix)
 {
   Hash_table *t = *table;
-  char *s = xstrdup (string);
+  char *s;
   char *e;
 
+  if (len)
+    {
+      s = xmalloc (len + 1);
+      memcpy (s, string, len);
+      s[len] = 0;
+    }
+  else
+    s = xstrdup (string);
+  
   if (! ((t
 	  || (*table = t = hash_initialize (0, 0, hash_string_hasher,
 					    hash_string_compare, 0)))
@@ -52,7 +64,11 @@ hash_string_insert (Hash_table **table, char const *string)
     xalloc_die ();
 
   if (e == s)
-    return 1;
+    {
+      if (return_prefix)
+	*return_prefix = s;
+      return 1;
+    }
   else
     {
       free (s);
@@ -60,6 +76,14 @@ hash_string_insert (Hash_table **table, char const *string)
     }
 }
 
+/* Return zero if TABLE contains a copy of STRING; otherwise, insert a
+   copy of STRING to TABLE and return 1.  */
+bool
+hash_string_insert (Hash_table **table, char const *string)
+{
+  return hash_string_insert_prefix (table, string, 0, NULL);
+}
+
 /* Return 1 if TABLE contains STRING.  */
 bool
 hash_string_lookup (Hash_table const *table, char const *string)
@@ -88,7 +112,8 @@ removed_prefixes_p (void)
    If ABSOLUTE_NAMES is 0, strip filesystem prefix from the file name. */
 
 char *
-safer_name_suffix (char const *file_name, bool link_target, bool absolute_names)
+safer_name_suffix (char const *file_name, bool link_target,
+		   bool absolute_names)
 {
   char const *p;
 
@@ -121,11 +146,9 @@ safer_name_suffix (char const *file_name, bool link_target, bool absolute_names)
 
       if (prefix_len)
 	{
-	  char *prefix = alloca (prefix_len + 1);
-	  memcpy (prefix, file_name, prefix_len);
-	  prefix[prefix_len] = '\0';
-
-	  if (hash_string_insert (&prefix_table[link_target], prefix))
+	  const char **prefix;
+	  if (hash_string_insert_prefix (&prefix_table[link_target], file_name,
+					 prefix_len, &prefix))
 	    {
 	      static char const *const diagnostic[] =
 	      {