diff --git a/src/libpspp/ext-array.c b/src/libpspp/ext-array.c
index 57ff8e4..682e677 100644
--- a/src/libpspp/ext-array.c
+++ b/src/libpspp/ext-array.c
@@ -36,6 +36,7 @@
 #include "gettext.h"
 #define _(msgid) gettext (msgid)
 
+
 struct ext_array
   {
     FILE *file;                 /* Underlying file. */
@@ -56,6 +57,7 @@ ext_array_create (void)
   if (ea->file == NULL)
     error (0, errno, _("failed to create temporary file"));
   ea->position = 0;
+  fprintf (stderr, "%s:%d Sizeof off_t: %d\n", __FILE__, __LINE__, sizeof (off_t));
   return ea;
 }
 
@@ -107,6 +109,7 @@ do_seek (const struct ext_array *ea_, off_t offset)
 static bool
 do_read (const struct ext_array *ea_, void *buffer, size_t bytes)
 {
+  off_t old_pos ;
   struct ext_array *ea = CONST_CAST (struct ext_array *, ea_);
 
   assert (!ext_array_error (ea));
@@ -120,7 +123,10 @@ do_read (const struct ext_array *ea_, void *buffer, size_t bytes)
         NOT_REACHED ();
       return false;
     }
+  old_pos = ea->position;
   ea->position += bytes;
+  if (ea->position < old_pos)
+    fprintf (stderr, "%s:%d ea->position has overflowed\n", __FILE__, __LINE__);
   return true;
 }
 
@@ -131,13 +137,20 @@ do_read (const struct ext_array *ea_, void *buffer, size_t bytes)
 static bool
 do_write (struct ext_array *ea, const void *buffer, size_t bytes)
 {
+  off_t old_pos;
+  int r = 0;
   assert (!ext_array_error (ea));
-  if (bytes > 0 && fwrite (buffer, bytes, 1, ea->file) != 1)
+
+  if (bytes > 0 && (r = fwrite (buffer, bytes, 1, ea->file)) != 1)
     {
-      error (0, errno, _("writing to temporary file"));
+      error (0, errno, _("writing to temporary file (Stream %p, %d items written)"), ea->file, r);
       return false;
     }
+  old_pos = ea->position;
   ea->position += bytes;
+  if (ea->position < old_pos)
+    fprintf (stderr, "%s:%d ea->position has overflowed\n", __FILE__, __LINE__);
+
   return true;
 }
 
diff --git a/src/libpspp/temp-file.c b/src/libpspp/temp-file.c
index d121cb9..adae44e 100644
--- a/src/libpspp/temp-file.c
+++ b/src/libpspp/temp-file.c
@@ -105,11 +105,16 @@ create_temp_file (void)
 
   file_name = xasprintf ("%s/%d", temp_dir->dir_name, idx++);
   register_temp_file (temp_dir, file_name);
+
   stream = fopen_temp (file_name, "wb+");
+  fprintf (stderr, "%s:%d Tmpfile \"%s\"; Stream %p\n", __FILE__, __LINE__, file_name, stream);
   if (stream == NULL)
     unregister_temp_file (temp_dir, file_name);
   else
-    setvbuf (stream, NULL, _IOFBF, 65536);
+    {
+      int x = setvbuf (stream, NULL, _IOFBF, 65536);
+      fprintf (stderr, "%s:%d setvbuf result %d\n", __FILE__, __LINE__, x);
+    }
 
   hmapx_insert (&map, file_name, hash_pointer (stream, 0));
 
@@ -124,6 +129,7 @@ close_temp_file (FILE *file)
     {
       struct hmapx_node *node = hmapx_first_with_hash (&map, hash_pointer (file, 0));
       char *fn = node->data;
+      fprintf (stderr, "%s:%d Closing and removing tempfile %s %p\n", __FILE__, __LINE__, fn, file);
       fclose_temp (file);
       cleanup_temp_file (temp_dir, fn); 
       hmapx_delete (&map, node);