readlink, getcwd memory leaks

[Kevin Ryde]

        * filesys.c (scm_getcwd, scm_readlink): Avoid memory leak on errors.

Unbounded growth can be seen with

        (while #t (false-if-exception (readlink "nosuchfile")))

and

        (mkdir "somedir")
        (chdir "somedir")
        (rmdir "../somedir")
        (while #t (false-if-exception (getcwd)))

This will be for the 1.6 branch too I think.

--- filesys.c.~1.119.~  2003-05-30 08:40:07.000000000 +1000
+++ filesys.c   2004-03-25 14:16:28.000000000 +1000
@@ -1,4 +1,4 @@
-/* Copyright (C) 1996,1997,1998,1999,2000,2001, 2002 Free Software Foundation, 
Inc.
+/* Copyright (C) 1996,1997,1998,1999,2000,2001, 2002, 2004 Free Software 
Foundation, Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -929,7 +929,12 @@
       wd = scm_malloc (size);
     }
   if (rv == 0)
-    SCM_SYSERROR;
+    {
+      int save_errno = errno;
+      free (wd);
+      errno = save_errno;
+      SCM_SYSERROR;
+    }
   result = scm_mem2string (wd, strlen (wd));
   free (wd);
   return result;
@@ -1349,7 +1354,12 @@
       buf = scm_malloc (size);
     }
   if (rv == -1)
-    SCM_SYSERROR;
+    {
+      int save_errno = errno;
+      free (buf);
+      errno = save_errno;
+      SCM_SYSERROR;
+    }
   result = scm_mem2string (buf, rv);
   free (buf);
   return result;