From f2d5acabd5602cde518ae18cc2c68d116d1e7f39 Mon Sep 17 00:00:00 2001
From: Cary R <cygcary@yahoo.com>
Date: Sun, 11 Apr 2010 23:39:08 -0700
Subject: [PATCH] Add support for vpiUserSystf iteration, etc.

This patch adds support for iterating over the list of vpiUserSystf
tasks/functions that have vpiUserDefn set. The vpiUserDefn property
is true by default, but you can call vpip_make_systf_system_defined()
to set this property false (will hide the vpiUserSystf object). All
the normal system tasks/functions have been modified to call this
procedure to remove them from the list of vpiUserSystf objects. Only
user defined system tasks or functions should appear in the list.

vpi_compare_objects() is just a simple are the two pointers the
same. This works correctly for the vpiUserSystf objects, but the
other handle objects have not been checked.
---
 vpi/sys_clog2.c      |   6 +-
 vpi/sys_convert.c    |  15 +++--
 vpi/sys_deposit.c    |   6 +-
 vpi/sys_display.c    | 124 +++++++++++++++++++++++------------
 vpi/sys_fileio.c     |  52 ++++++++++-----
 vpi/sys_finish.c     |   9 ++-
 vpi/sys_icarus.c     | 150 ++++++++++++++++++++++++++++---------------
 vpi/sys_lxt.c        |  24 ++++---
 vpi/sys_lxt2.c       |  22 +++++--
 vpi/sys_plusargs.c   |  10 +--
 vpi/sys_random.c     |  33 ++++++----
 vpi/sys_random_mti.c |   9 ++-
 vpi/sys_readmem.c    |  16 +++--
 vpi/sys_scanf.c      |   7 +-
 vpi/sys_sdf.c        |   4 +-
 vpi/sys_time.c       |  18 ++++--
 vpi/sys_vcd.c        |  24 ++++---
 vpi/sys_vcdoff.c     |  24 ++++---
 vpi/v2005_math.c     |   9 ++-
 vpi/va_math.c        |   9 ++-
 vpi/vams_simparam.c  |   9 ++-
 vpi_user.h           |   1 +
 vvp/vpi_priv.cc      |  13 +++-
 vvp/vpi_priv.h       |   3 +
 vvp/vpi_tasks.cc     |  85 ++++++++++++++++++++++--
 vvp/vvp.def          |   5 +-
 26 files changed, 485 insertions(+), 202 deletions(-)

diff --git a/vpi/sys_clog2.c b/vpi/sys_clog2.c
index 34c7442a3..e4921152a 100644
--- a/vpi/sys_clog2.c
+++ b/vpi/sys_clog2.c
@@ -1,5 +1,5 @@
 /*
- *  Copyright (C) 2008-2009  Cary R. (cygcary@yahoo.com)
+ *  Copyright (C) 2008-2010  Cary R. (cygcary@yahoo.com)
  *
  *  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
@@ -133,6 +133,7 @@ static PLI_INT32 sys_clog2_calltf(PLI_BYTE8 *name)
 void sys_clog2_register(void)
 {
       s_vpi_systf_data tf_data;
+      vpiHandle res;
 
       tf_data.type        = vpiSysFunc;
       tf_data.sysfunctype = vpiIntFunc;
@@ -141,5 +142,6 @@ void sys_clog2_register(void)
       tf_data.sizetf      = 0;
       tf_data.tfname      = "$clog2";
       tf_data.user_data   = 0;
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 }
diff --git a/vpi/sys_convert.c b/vpi/sys_convert.c
index d8dd175c6..efcf5bda9 100644
--- a/vpi/sys_convert.c
+++ b/vpi/sys_convert.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003-2009 Michael Ruff (mruff  at chiaro.com)
+ * Copyright (c) 2003-2010 Michael Ruff (mruff  at chiaro.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -229,6 +229,7 @@ static PLI_INT32 sys_rtoi_calltf(PLI_BYTE8*user)
 void sys_convert_register()
 {
       s_vpi_systf_data tf_data;
+      vpiHandle res;
 
       tf_data.type      = vpiSysFunc;
       tf_data.user_data = "$bitstoreal";
@@ -236,7 +237,8 @@ void sys_convert_register()
       tf_data.sizetf    = sizetf_64;
       tf_data.compiletf = sys_convert_compiletf;
       tf_data.calltf    = sys_bitstoreal_calltf;
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysFunc;
       tf_data.user_data = "$itor";
@@ -244,7 +246,8 @@ void sys_convert_register()
       tf_data.sizetf    = sizetf_64;
       tf_data.compiletf = sys_convert_compiletf;
       tf_data.calltf    = sys_itor_calltf;
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysFunc;
       tf_data.user_data = "$realtobits";
@@ -252,7 +255,8 @@ void sys_convert_register()
       tf_data.sizetf    = sizetf_64;
       tf_data.compiletf = sys_convert_compiletf;
       tf_data.calltf    = sys_realtobits_calltf;
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysFunc;
       tf_data.user_data = "$rtoi";
@@ -260,6 +264,7 @@ void sys_convert_register()
       tf_data.sizetf    = sizetf_32;
       tf_data.compiletf = sys_convert_compiletf;
       tf_data.calltf    = sys_rtoi_calltf;
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 }
 
diff --git a/vpi/sys_deposit.c b/vpi/sys_deposit.c
index 401916aa2..f7b7a312c 100644
--- a/vpi/sys_deposit.c
+++ b/vpi/sys_deposit.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999-2009 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 1999-2010 Stephen Williams (steve@icarus.com)
  * Copyright (c) 2000 Stephan Boettcher <stephan@nevis.columbia.edu>
  *
  *    This source code is free software; you can redistribute it
@@ -95,6 +95,7 @@ static PLI_INT32 sys_deposit_calltf(PLI_BYTE8 *name)
 void sys_deposit_register()
 {
       s_vpi_systf_data tf_data;
+      vpiHandle res;
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$deposit";
@@ -102,6 +103,7 @@ void sys_deposit_register()
       tf_data.compiletf = sys_deposit_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$deposit";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 }
 
diff --git a/vpi/sys_display.c b/vpi/sys_display.c
index dea997f67..f23ec6bda 100644
--- a/vpi/sys_display.c
+++ b/vpi/sys_display.c
@@ -1971,6 +1971,7 @@ void sys_display_register()
 {
       s_cb_data cb_data;
       s_vpi_systf_data tf_data;
+      vpiHandle res;
 
       /*============================== display */
       tf_data.type      = vpiSysTask;
@@ -1979,7 +1980,8 @@ void sys_display_register()
       tf_data.compiletf = sys_display_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$display";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$displayh";
@@ -1987,7 +1989,8 @@ void sys_display_register()
       tf_data.compiletf = sys_display_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$displayh";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$displayo";
@@ -1995,7 +1998,8 @@ void sys_display_register()
       tf_data.compiletf = sys_display_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$displayo";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$displayb";
@@ -2003,7 +2007,8 @@ void sys_display_register()
       tf_data.compiletf = sys_display_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$displayb";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================== write */
       tf_data.type      = vpiSysTask;
@@ -2012,7 +2017,8 @@ void sys_display_register()
       tf_data.compiletf = sys_display_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$write";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$writeh";
@@ -2020,7 +2026,8 @@ void sys_display_register()
       tf_data.compiletf = sys_display_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$writeh";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$writeo";
@@ -2028,7 +2035,8 @@ void sys_display_register()
       tf_data.compiletf = sys_display_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$writeo";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$writeb";
@@ -2036,7 +2044,8 @@ void sys_display_register()
       tf_data.compiletf = sys_display_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$writeb";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================== strobe */
       tf_data.type      = vpiSysTask;
@@ -2045,7 +2054,8 @@ void sys_display_register()
       tf_data.compiletf = sys_strobe_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$strobe";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$strobeh";
@@ -2053,7 +2063,8 @@ void sys_display_register()
       tf_data.compiletf = sys_strobe_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$strobeh";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$strobeo";
@@ -2061,7 +2072,8 @@ void sys_display_register()
       tf_data.compiletf = sys_strobe_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$strobeo";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$strobeb";
@@ -2069,7 +2081,8 @@ void sys_display_register()
       tf_data.compiletf = sys_strobe_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$strobeb";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================== fstrobe */
       tf_data.type      = vpiSysTask;
@@ -2078,7 +2091,8 @@ void sys_display_register()
       tf_data.compiletf = sys_strobe_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$fstrobe";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$fstrobeh";
@@ -2086,7 +2100,8 @@ void sys_display_register()
       tf_data.compiletf = sys_strobe_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$fstrobeh";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$fstrobeo";
@@ -2094,7 +2109,8 @@ void sys_display_register()
       tf_data.compiletf = sys_strobe_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$fstrobeo";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$fstrobeb";
@@ -2102,7 +2118,8 @@ void sys_display_register()
       tf_data.compiletf = sys_strobe_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$fstrobeb";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================== monitor */
       tf_data.type      = vpiSysTask;
@@ -2111,7 +2128,8 @@ void sys_display_register()
       tf_data.compiletf = sys_monitor_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$monitor";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$monitorh";
@@ -2119,7 +2137,8 @@ void sys_display_register()
       tf_data.compiletf = sys_monitor_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$monitorh";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$monitoro";
@@ -2127,7 +2146,8 @@ void sys_display_register()
       tf_data.compiletf = sys_monitor_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$monitoro";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$monitorb";
@@ -2135,7 +2155,8 @@ void sys_display_register()
       tf_data.compiletf = sys_monitor_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$monitorb";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$monitoron";
@@ -2143,7 +2164,8 @@ void sys_display_register()
       tf_data.compiletf = sys_no_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$monitoron";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$monitoroff";
@@ -2151,7 +2173,8 @@ void sys_display_register()
       tf_data.compiletf = sys_no_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$monitoroff";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================== fdisplay */
       tf_data.type      = vpiSysTask;
@@ -2160,7 +2183,8 @@ void sys_display_register()
       tf_data.compiletf = sys_display_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$fdisplay";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$fdisplayh";
@@ -2168,7 +2192,8 @@ void sys_display_register()
       tf_data.compiletf = sys_display_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$fdisplayh";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$fdisplayo";
@@ -2176,7 +2201,8 @@ void sys_display_register()
       tf_data.compiletf = sys_display_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$fdisplayo";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$fdisplayb";
@@ -2184,7 +2210,8 @@ void sys_display_register()
       tf_data.compiletf = sys_display_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$fdisplayb";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================== fwrite */
       tf_data.type      = vpiSysTask;
@@ -2193,7 +2220,8 @@ void sys_display_register()
       tf_data.compiletf = sys_display_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$fwrite";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$fwriteh";
@@ -2201,7 +2229,8 @@ void sys_display_register()
       tf_data.compiletf = sys_display_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$fwriteh";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$fwriteo";
@@ -2209,7 +2238,8 @@ void sys_display_register()
       tf_data.compiletf = sys_display_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$fwriteo";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$fwriteb";
@@ -2217,7 +2247,8 @@ void sys_display_register()
       tf_data.compiletf = sys_display_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$fwriteb";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================== swrite */
       tf_data.type      = vpiSysTask;
@@ -2226,7 +2257,8 @@ void sys_display_register()
       tf_data.compiletf = sys_swrite_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$swrite";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$swriteh";
@@ -2234,7 +2266,8 @@ void sys_display_register()
       tf_data.compiletf = sys_swrite_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$swriteh";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$swriteo";
@@ -2242,7 +2275,8 @@ void sys_display_register()
       tf_data.compiletf = sys_swrite_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$swriteo";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$swriteb";
@@ -2250,7 +2284,8 @@ void sys_display_register()
       tf_data.compiletf = sys_swrite_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$swriteb";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$sformat";
@@ -2258,7 +2293,8 @@ void sys_display_register()
       tf_data.compiletf = sys_sformat_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$sformat";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================ timeformat */
       tf_data.type      = vpiSysTask;
@@ -2267,7 +2303,8 @@ void sys_display_register()
       tf_data.compiletf = sys_timeformat_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$timeformat";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$printtimescale";
@@ -2275,7 +2312,8 @@ void sys_display_register()
       tf_data.compiletf = sys_printtimescale_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$printtimescale";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================ severity tasks */
       tf_data.type      = vpiSysTask;
@@ -2284,7 +2322,8 @@ void sys_display_register()
       tf_data.compiletf = sys_fatal_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$fatal";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$error";
@@ -2292,7 +2331,8 @@ void sys_display_register()
       tf_data.compiletf = sys_display_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$error";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$warning";
@@ -2300,7 +2340,8 @@ void sys_display_register()
       tf_data.compiletf = sys_display_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$warning";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$info";
@@ -2308,7 +2349,8 @@ void sys_display_register()
       tf_data.compiletf = sys_display_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$info";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       cb_data.reason = cbEndOfCompile;
       cb_data.time = 0;
diff --git a/vpi/sys_fileio.c b/vpi/sys_fileio.c
index 938dee292..89329aa32 100644
--- a/vpi/sys_fileio.c
+++ b/vpi/sys_fileio.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003-2009 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2003-2010 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -1058,6 +1058,7 @@ static PLI_INT32 sys_ferror_calltf(PLI_BYTE8 *name)
 void sys_fileio_register()
 {
       s_vpi_systf_data tf_data;
+      vpiHandle res;
 
       /*============================== fopen */
       tf_data.type        = vpiSysFunc;
@@ -1067,7 +1068,8 @@ void sys_fileio_register()
       tf_data.compiletf   = sys_fopen_compiletf;
       tf_data.sizetf      = 0;
       tf_data.user_data   = "$fopen";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================== fopenr */
       tf_data.type        = vpiSysFunc;
@@ -1077,17 +1079,20 @@ void sys_fileio_register()
       tf_data.compiletf   = sys_one_string_arg_compiletf;
       tf_data.sizetf      = 0;
       tf_data.user_data   = "$fopenr";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================== fopenw */
       tf_data.tfname      = "$fopenw";
       tf_data.user_data   = "$fopenw";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================== fopena */
       tf_data.tfname      = "$fopena";
       tf_data.user_data   = "$fopena";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================== fclose */
       tf_data.type      = vpiSysTask;
@@ -1096,7 +1101,8 @@ void sys_fileio_register()
       tf_data.compiletf = sys_one_numeric_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$fclose";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================== fflush */
       tf_data.type      = vpiSysTask;
@@ -1105,7 +1111,8 @@ void sys_fileio_register()
       tf_data.compiletf = sys_one_opt_numeric_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$fflush";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================== fgetc */
       tf_data.type      = vpiSysFunc;
@@ -1115,7 +1122,8 @@ void sys_fileio_register()
       tf_data.compiletf = sys_one_numeric_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$fgetc";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================== fgets */
       tf_data.type      = vpiSysFunc;
@@ -1125,7 +1133,8 @@ void sys_fileio_register()
       tf_data.compiletf = sys_fgets_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$fgets";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================== fread */
       tf_data.type      = vpiSysFunc;
@@ -1135,7 +1144,8 @@ void sys_fileio_register()
       tf_data.compiletf = sys_fread_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$fread";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================== ungetc */
       tf_data.type      = vpiSysFunc;
@@ -1145,7 +1155,8 @@ void sys_fileio_register()
       tf_data.compiletf = sys_two_numeric_args_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$ungetc";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================== ftell */
       tf_data.type      = vpiSysFunc;
@@ -1155,7 +1166,8 @@ void sys_fileio_register()
       tf_data.compiletf = sys_one_numeric_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$ftell";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================== fseek */
       tf_data.type      = vpiSysFunc;
@@ -1165,7 +1177,9 @@ void sys_fileio_register()
       tf_data.compiletf = sys_fseek_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$fseek";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
+      vpip_make_systf_system_defined(res);
 
       /*============================== rewind */
       tf_data.type      = vpiSysFunc;
@@ -1175,7 +1189,8 @@ void sys_fileio_register()
       tf_data.compiletf = sys_one_numeric_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$rewind";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================== ferror */
       tf_data.type      = vpiSysFunc;
@@ -1185,7 +1200,8 @@ void sys_fileio_register()
       tf_data.compiletf = sys_ferror_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$ferror";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /* $feof() is from 1364-2005. */
       /*============================== feof */
@@ -1196,7 +1212,8 @@ void sys_fileio_register()
       tf_data.compiletf = sys_one_numeric_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$feof";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /* Icarus specific. */
       /*============================== fputc */
@@ -1207,5 +1224,6 @@ void sys_fileio_register()
       tf_data.compiletf = sys_two_numeric_args_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$fputc";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 }
diff --git a/vpi/sys_finish.c b/vpi/sys_finish.c
index f55dd312e..2eaceef80 100644
--- a/vpi/sys_finish.c
+++ b/vpi/sys_finish.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999-2008 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 1999-2010 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -51,6 +51,7 @@ static PLI_INT32 sys_finish_calltf(PLI_BYTE8 *name)
 void sys_finish_register()
 {
       s_vpi_systf_data tf_data;
+      vpiHandle res;
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$finish";
@@ -58,7 +59,8 @@ void sys_finish_register()
       tf_data.compiletf = sys_one_opt_numeric_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$finish";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$stop";
@@ -66,5 +68,6 @@ void sys_finish_register()
       tf_data.compiletf = sys_one_opt_numeric_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$stop";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 }
diff --git a/vpi/sys_icarus.c b/vpi/sys_icarus.c
index 8551057a8..7c194ae93 100644
--- a/vpi/sys_icarus.c
+++ b/vpi/sys_icarus.c
@@ -1,5 +1,5 @@
 /*
- *  Copyright (C) 2008-2009  Cary R. (cygcary@yahoo.com)
+ *  Copyright (C) 2008-2010  Cary R. (cygcary@yahoo.com)
  *
  *  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
@@ -74,6 +74,7 @@ static PLI_INT32 missing_optional_compiletf(PLI_BYTE8* name)
 void sys_special_register(void)
 {
       s_vpi_systf_data tf_data;
+      vpiHandle res;
 
       tf_data.type        = vpiSysTask;
       tf_data.calltf      = finish_and_return_calltf;
@@ -81,7 +82,8 @@ void sys_special_register(void)
       tf_data.sizetf      = 0;
       tf_data.tfname      = "$finish_and_return";
       tf_data.user_data   = "$finish_and_return";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
 	/* These tasks are not currently implemented. */
       tf_data.type        = vpiSysTask;
@@ -91,127 +93,158 @@ void sys_special_register(void)
 
       tf_data.tfname      = "$fmonitor";
       tf_data.user_data   = "$fmonitor";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$fmonitorb";
       tf_data.user_data   = "$fmonitorb";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$fmonitoro";
       tf_data.user_data   = "$fmonitoro";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$fmonitorh";
       tf_data.user_data   = "$fmonitorh";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$async$and$array";
       tf_data.user_data   = "$async$and$array";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$async$nand$array";
       tf_data.user_data   = "$async$nand$array";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$async$or$array";
       tf_data.user_data   = "$async$or$array";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$async$nor$array";
       tf_data.user_data   = "$async$nor$array";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$async$and$plane";
       tf_data.user_data   = "$async$and$plane";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$async$nand$plane";
       tf_data.user_data   = "$async$nand$plane";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$async$or$plane";
       tf_data.user_data   = "$async$or$plane";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$async$nor$plane";
       tf_data.user_data   = "$async$nor$plane";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$sync$and$array";
       tf_data.user_data   = "$sync$and$array";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$sync$nand$array";
       tf_data.user_data   = "$sync$nand$array";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$sync$or$array";
       tf_data.user_data   = "$sync$or$array";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$sync$nor$array";
       tf_data.user_data   = "$sync$nor$array";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$sync$and$plane";
       tf_data.user_data   = "$sync$and$plane";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$sync$nand$plane";
       tf_data.user_data   = "$sync$nand$plane";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$sync$or$plane";
       tf_data.user_data   = "$sync$or$plane";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$sync$nor$plane";
       tf_data.user_data   = "$sync$nor$plane";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$q_initialize";
       tf_data.user_data   = "$q_initialize";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$q_add";
       tf_data.user_data   = "$q_add";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$q_remove";
       tf_data.user_data   = "$q_remove";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$q_full";
       tf_data.user_data   = "$q_full";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$q_exam";
       tf_data.user_data   = "$q_exam";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$dumpports";
       tf_data.user_data   = "$dumpports";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$dumpportsoff";
       tf_data.user_data   = "$dumpportsoff";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$dumpportson";
       tf_data.user_data   = "$dumpportson";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$dumpportsall";
       tf_data.user_data   = "$dumpportsall";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$dumpportslimit";
       tf_data.user_data   = "$dumpportslimit";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$dumpportsflush";
       tf_data.user_data   = "$dumpportsflush";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
 	/* The following optional system tasks/functions are not implemented
 	 * in Icarus Verilog (from Annex C 1364-2005). */
@@ -222,59 +255,73 @@ void sys_special_register(void)
 
       tf_data.tfname      = "$input";
       tf_data.user_data   = "$input";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$key";
       tf_data.user_data   = "$key";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$nokey";
       tf_data.user_data   = "$nokey";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$list";
       tf_data.user_data   = "$list";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$log";
       tf_data.user_data   = "$log";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$nolog";
       tf_data.user_data   = "$nolog";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$save";
       tf_data.user_data   = "$save";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$restart";
       tf_data.user_data   = "$restart";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$incsave";
       tf_data.user_data   = "$incsave";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$scope";
       tf_data.user_data   = "$scope";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$showscopes";
       tf_data.user_data   = "$showscopes";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$showvars";
       tf_data.user_data   = "$showvars";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$sreadmemb";
       tf_data.user_data   = "$sreadmemb";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$sreadmemh";
       tf_data.user_data   = "$sreadmemh";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
 	/* Optional functions. */
       tf_data.type = vpiSysFunc;
@@ -282,13 +329,16 @@ void sys_special_register(void)
 
       tf_data.tfname      = "$countdrivers";
       tf_data.user_data   = "$countdrivers";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$getpattern";
       tf_data.user_data   = "$getpattern";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.tfname      = "$scale";
       tf_data.user_data   = "$scale";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 }
diff --git a/vpi/sys_lxt.c b/vpi/sys_lxt.c
index 1db04ccf7..1fadd3945 100644
--- a/vpi/sys_lxt.c
+++ b/vpi/sys_lxt.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002-2009 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2002-2010 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -778,6 +778,7 @@ void sys_lxt_register()
       int idx;
       struct t_vpi_vlog_info vlog_info;
       s_vpi_systf_data tf_data;
+      vpiHandle res;
 
 
 	/* Scan the extended arguments, looking for lxt optimization
@@ -802,7 +803,8 @@ void sys_lxt_register()
       tf_data.compiletf = sys_no_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpall";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumpfile";
@@ -810,7 +812,8 @@ void sys_lxt_register()
       tf_data.compiletf = sys_one_string_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpfile";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumpflush";
@@ -818,7 +821,8 @@ void sys_lxt_register()
       tf_data.compiletf = sys_no_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpflush";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumplimit";
@@ -826,7 +830,8 @@ void sys_lxt_register()
       tf_data.compiletf = sys_one_numeric_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumplimit";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumpoff";
@@ -834,7 +839,8 @@ void sys_lxt_register()
       tf_data.compiletf = sys_no_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpoff";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumpon";
@@ -842,7 +848,8 @@ void sys_lxt_register()
       tf_data.compiletf = sys_no_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpon";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumpvars";
@@ -850,5 +857,6 @@ void sys_lxt_register()
       tf_data.compiletf = sys_dumpvars_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpvars";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 }
diff --git a/vpi/sys_lxt2.c b/vpi/sys_lxt2.c
index 14e90a2ec..e8c36e219 100644
--- a/vpi/sys_lxt2.c
+++ b/vpi/sys_lxt2.c
@@ -878,6 +878,7 @@ void sys_lxt2_register()
       int idx;
       struct t_vpi_vlog_info vlog_info;
       s_vpi_systf_data tf_data;
+      vpiHandle res;
 
 
 	/* Scan the extended arguments, looking for lxt optimization
@@ -902,7 +903,8 @@ void sys_lxt2_register()
       tf_data.compiletf = sys_no_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpall";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumpfile";
@@ -910,7 +912,8 @@ void sys_lxt2_register()
       tf_data.compiletf = sys_one_string_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpfile";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumpflush";
@@ -918,7 +921,8 @@ void sys_lxt2_register()
       tf_data.compiletf = sys_no_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpflush";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumplimit";
@@ -926,7 +930,8 @@ void sys_lxt2_register()
       tf_data.compiletf = sys_one_numeric_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumplimit";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumpoff";
@@ -934,7 +939,8 @@ void sys_lxt2_register()
       tf_data.compiletf = sys_no_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpoff";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumpon";
@@ -942,7 +948,8 @@ void sys_lxt2_register()
       tf_data.compiletf = sys_no_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpon";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumpvars";
@@ -950,5 +957,6 @@ void sys_lxt2_register()
       tf_data.compiletf = sys_dumpvars_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpvars";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 }
diff --git a/vpi/sys_plusargs.c b/vpi/sys_plusargs.c
index 09ee65f4a..5c1257b85 100644
--- a/vpi/sys_plusargs.c
+++ b/vpi/sys_plusargs.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002-2008 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2002-2010 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -371,7 +371,7 @@ static PLI_INT32 sys_value_plusargs_calltf(PLI_BYTE8*name)
 void sys_plusargs_register()
 {
       s_vpi_systf_data tf_data;
-
+      vpiHandle res;
 
       tf_data.type        = vpiSysFunc;
       tf_data.sysfunctype = vpiIntFunc;
@@ -380,7 +380,8 @@ void sys_plusargs_register()
       tf_data.compiletf   = sys_one_string_arg_compiletf;
       tf_data.sizetf      = 0;
       tf_data.user_data   = "$test$plusargs";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type        = vpiSysFunc;
       tf_data.sysfunctype = vpiIntFunc;
@@ -389,6 +390,7 @@ void sys_plusargs_register()
       tf_data.compiletf   = sys_value_plusargs_compiletf;
       tf_data.sizetf      = 0;
       tf_data.user_data   = "$value$plusargs";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
 }
diff --git a/vpi/sys_random.c b/vpi/sys_random.c
index bf9f05e22..84a56cfc8 100644
--- a/vpi/sys_random.c
+++ b/vpi/sys_random.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000-2009 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2000-2010 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -896,6 +896,7 @@ static PLI_INT32 sys_rand_func_sizetf(PLI_BYTE8 *x)
 void sys_random_register()
 {
       s_vpi_systf_data tf_data;
+      vpiHandle res;
 
       tf_data.type = vpiSysFunc;
       tf_data.sysfunctype = vpiSysFuncInt;
@@ -904,7 +905,8 @@ void sys_random_register()
       tf_data.compiletf = sys_random_compiletf;
       tf_data.sizetf = sys_rand_func_sizetf;
       tf_data.user_data = "$random";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /* From System Verilog 3.1a. */
       tf_data.type = vpiSysFunc;
@@ -914,7 +916,8 @@ void sys_random_register()
       tf_data.compiletf = sys_random_compiletf;
       tf_data.sizetf = sys_rand_func_sizetf;
       tf_data.user_data = "$urandom";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /* From System Verilog 3.1a. */
       tf_data.type = vpiSysFunc;
@@ -924,7 +927,8 @@ void sys_random_register()
       tf_data.compiletf = sys_urandom_range_compiletf;
       tf_data.sizetf = sys_rand_func_sizetf;
       tf_data.user_data = "$urandom_range";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type = vpiSysFunc;
       tf_data.sysfunctype = vpiSysFuncInt;
@@ -933,7 +937,8 @@ void sys_random_register()
       tf_data.compiletf = sys_rand_three_args_compiletf;
       tf_data.sizetf = sys_rand_func_sizetf;
       tf_data.user_data = "$dist_uniform";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type = vpiSysFunc;
       tf_data.sysfunctype = vpiSysFuncInt;
@@ -942,7 +947,8 @@ void sys_random_register()
       tf_data.compiletf = sys_rand_three_args_compiletf;
       tf_data.sizetf = sys_rand_func_sizetf;
       tf_data.user_data = "$dist_normal";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type = vpiSysFunc;
       tf_data.sysfunctype = vpiSysFuncInt;
@@ -951,7 +957,8 @@ void sys_random_register()
       tf_data.compiletf = sys_rand_two_args_compiletf;
       tf_data.sizetf = sys_rand_func_sizetf;
       tf_data.user_data = "$dist_exponential";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type = vpiSysFunc;
       tf_data.sysfunctype = vpiSysFuncInt;
@@ -960,7 +967,8 @@ void sys_random_register()
       tf_data.compiletf = sys_rand_two_args_compiletf;
       tf_data.sizetf = sys_rand_func_sizetf;
       tf_data.user_data = "$dist_poisson";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type = vpiSysFunc;
       tf_data.sysfunctype = vpiSysFuncInt;
@@ -969,7 +977,8 @@ void sys_random_register()
       tf_data.compiletf = sys_rand_two_args_compiletf;
       tf_data.sizetf = sys_rand_func_sizetf;
       tf_data.user_data = "$dist_chi_square";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type = vpiSysFunc;
       tf_data.sysfunctype = vpiSysFuncInt;
@@ -978,7 +987,8 @@ void sys_random_register()
       tf_data.compiletf = sys_rand_two_args_compiletf;
       tf_data.sizetf = sys_rand_func_sizetf;
       tf_data.user_data = "$dist_t";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type = vpiSysFunc;
       tf_data.sysfunctype = vpiSysFuncInt;
@@ -987,5 +997,6 @@ void sys_random_register()
       tf_data.compiletf = sys_rand_three_args_compiletf;
       tf_data.sizetf = sys_rand_func_sizetf;
       tf_data.user_data = "$dist_erlang";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 }
diff --git a/vpi/sys_random_mti.c b/vpi/sys_random_mti.c
index 7294e0f6a..30d7dd341 100644
--- a/vpi/sys_random_mti.c
+++ b/vpi/sys_random_mti.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000-2009 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2000-2010 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -145,6 +145,7 @@ static PLI_INT32 sys_mti_random_calltf(PLI_BYTE8*name)
 void sys_random_mti_register()
 {
       s_vpi_systf_data tf_data;
+      vpiHandle res;
 
       tf_data.type        = vpiSysFunc;
       tf_data.sysfunctype = vpiSysFuncInt;
@@ -152,7 +153,8 @@ void sys_random_mti_register()
       tf_data.calltf      = sys_mti_random_calltf;
       tf_data.compiletf   = sys_random_compiletf;
       tf_data.user_data   = "$mti_random";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type        = vpiSysFunc;
       tf_data.sysfunctype = vpiSysFuncInt;
@@ -160,6 +162,7 @@ void sys_random_mti_register()
       tf_data.calltf      = sys_mti_dist_uniform_calltf;
       tf_data.compiletf   = sys_rand_three_args_compiletf;
       tf_data.user_data   = "$mti_dist_uniform";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 }
 
diff --git a/vpi/sys_readmem.c b/vpi/sys_readmem.c
index 638d2ee83..ef1a761ae 100644
--- a/vpi/sys_readmem.c
+++ b/vpi/sys_readmem.c
@@ -571,6 +571,7 @@ static PLI_INT32 sys_writemem_calltf(PLI_BYTE8*name)
 void sys_readmem_register()
 {
       s_vpi_systf_data tf_data;
+      vpiHandle res;
       s_cb_data cb_data;
 
       tf_data.type      = vpiSysTask;
@@ -579,7 +580,8 @@ void sys_readmem_register()
       tf_data.compiletf = sys_mem_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$readmemh";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$readmemb";
@@ -587,7 +589,8 @@ void sys_readmem_register()
       tf_data.compiletf = sys_mem_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$readmemb";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$readmempath";
@@ -595,7 +598,8 @@ void sys_readmem_register()
       tf_data.compiletf = sys_one_string_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$readmempath";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$writememh";
@@ -603,7 +607,8 @@ void sys_readmem_register()
       tf_data.compiletf = sys_mem_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$writememh";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$writememb";
@@ -611,7 +616,8 @@ void sys_readmem_register()
       tf_data.compiletf = sys_mem_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$writememb";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       cb_data.reason = cbEndOfSimulation;
       cb_data.time = 0;
diff --git a/vpi/sys_scanf.c b/vpi/sys_scanf.c
index 52cd923ee..0c0d10b19 100644
--- a/vpi/sys_scanf.c
+++ b/vpi/sys_scanf.c
@@ -727,6 +727,7 @@ static PLI_INT32 sys_sscanf_calltf(PLI_BYTE8*name)
 void sys_scanf_register()
 {
       s_vpi_systf_data tf_data;
+      vpiHandle res;
 
       /*============================== fscanf */
       tf_data.type        = vpiSysFunc;
@@ -736,7 +737,8 @@ void sys_scanf_register()
       tf_data.compiletf   = sys_fscanf_compiletf;
       tf_data.sizetf      = 0;
       tf_data.user_data   = "$fscanf";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       /*============================== sscanf */
       tf_data.type        = vpiSysFunc;
@@ -746,5 +748,6 @@ void sys_scanf_register()
       tf_data.compiletf   = sys_sscanf_compiletf;
       tf_data.sizetf      = 0;
       tf_data.user_data   = "$sscanf";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 }
diff --git a/vpi/sys_sdf.c b/vpi/sys_sdf.c
index 139ebcc74..622cc3468 100644
--- a/vpi/sys_sdf.c
+++ b/vpi/sys_sdf.c
@@ -328,6 +328,7 @@ static PLI_INT32 sys_sdf_annotate_calltf(PLI_BYTE8*name)
 void sys_sdf_register()
 {
       s_vpi_systf_data tf_data;
+      vpiHandle res;
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$sdf_annotate";
@@ -335,5 +336,6 @@ void sys_sdf_register()
       tf_data.compiletf = sys_sdf_annotate_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$sdf_annotate";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 }
diff --git a/vpi/sys_time.c b/vpi/sys_time.c
index 83ac46407..28688fe7b 100644
--- a/vpi/sys_time.c
+++ b/vpi/sys_time.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000-2009 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2000-2010 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -111,6 +111,7 @@ static PLI_INT32 sys_realtime_calltf(PLI_BYTE8*name)
 void sys_time_register()
 {
       s_vpi_systf_data tf_data;
+      vpiHandle res;
 
       tf_data.type        = vpiSysFunc;
       tf_data.tfname      = "$time";
@@ -119,7 +120,8 @@ void sys_time_register()
       tf_data.compiletf   = sys_no_arg_compiletf;
       tf_data.sizetf      = 0;
       tf_data.user_data   = "$time";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type        = vpiSysFunc;
       tf_data.tfname      = "$realtime";
@@ -128,7 +130,8 @@ void sys_time_register()
       tf_data.compiletf   = sys_no_arg_compiletf;
       tf_data.sizetf      = 0;
       tf_data.user_data   = "$realtime";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type        = vpiSysFunc;
       tf_data.tfname      = "$stime";
@@ -137,7 +140,8 @@ void sys_time_register()
       tf_data.compiletf   = sys_no_arg_compiletf;
       tf_data.sizetf      = 0;
       tf_data.user_data   = "$stime";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type        = vpiSysFunc;
       tf_data.tfname      = "$simtime";
@@ -146,7 +150,8 @@ void sys_time_register()
       tf_data.compiletf   = sys_no_arg_compiletf;
       tf_data.sizetf      = 0;
       tf_data.user_data   = "$simtime";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type        = vpiSysFunc;
       tf_data.tfname      = "$abstime";
@@ -155,5 +160,6 @@ void sys_time_register()
       tf_data.compiletf   = sys_no_arg_compiletf;
       tf_data.sizetf      = 0;
       tf_data.user_data   = "$abstime";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 }
diff --git a/vpi/sys_vcd.c b/vpi/sys_vcd.c
index 10465c668..027c89817 100644
--- a/vpi/sys_vcd.c
+++ b/vpi/sys_vcd.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999-2009 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 1999-2010 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -840,6 +840,7 @@ static PLI_INT32 sys_dumpvars_calltf(PLI_BYTE8*name)
 void sys_vcd_register()
 {
       s_vpi_systf_data tf_data;
+      vpiHandle res;
 
       /* All the compiletf routines are located in vcd_priv.c. */
 
@@ -849,7 +850,8 @@ void sys_vcd_register()
       tf_data.compiletf = sys_no_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpall";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumpfile";
@@ -857,7 +859,8 @@ void sys_vcd_register()
       tf_data.compiletf = sys_one_string_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpfile";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumpflush";
@@ -865,7 +868,8 @@ void sys_vcd_register()
       tf_data.compiletf = sys_no_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpflush";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumplimit";
@@ -873,7 +877,8 @@ void sys_vcd_register()
       tf_data.compiletf = sys_one_numeric_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumplimit";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumpoff";
@@ -881,7 +886,8 @@ void sys_vcd_register()
       tf_data.compiletf = sys_no_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpoff";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumpon";
@@ -889,7 +895,8 @@ void sys_vcd_register()
       tf_data.compiletf = sys_no_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpon";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumpvars";
@@ -897,5 +904,6 @@ void sys_vcd_register()
       tf_data.compiletf = sys_dumpvars_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpvars";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 }
diff --git a/vpi/sys_vcdoff.c b/vpi/sys_vcdoff.c
index 49e8d5c45..eb30eedac 100644
--- a/vpi/sys_vcdoff.c
+++ b/vpi/sys_vcdoff.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003-2008 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2003-2010 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -55,6 +55,7 @@ static PLI_INT32 sys_dumpvars_calltf(PLI_BYTE8*name)
 void sys_vcdoff_register()
 {
       s_vpi_systf_data tf_data;
+      vpiHandle res;
 
       /* All the compiletf routines are located in vcd_priv.c. */
 
@@ -64,7 +65,8 @@ void sys_vcdoff_register()
       tf_data.compiletf = sys_no_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpall";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumpfile";
@@ -72,7 +74,8 @@ void sys_vcdoff_register()
       tf_data.compiletf = sys_one_string_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpfile";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumpflush";
@@ -80,7 +83,8 @@ void sys_vcdoff_register()
       tf_data.compiletf = sys_no_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpflush";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumplimit";
@@ -88,7 +92,8 @@ void sys_vcdoff_register()
       tf_data.compiletf = sys_one_numeric_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumplimit";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumpoff";
@@ -96,7 +101,8 @@ void sys_vcdoff_register()
       tf_data.compiletf = sys_no_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpoff";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumpon";
@@ -104,7 +110,8 @@ void sys_vcdoff_register()
       tf_data.compiletf = sys_no_arg_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpon";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type      = vpiSysTask;
       tf_data.tfname    = "$dumpvars";
@@ -112,5 +119,6 @@ void sys_vcdoff_register()
       tf_data.compiletf = sys_dumpvars_compiletf;
       tf_data.sizetf    = 0;
       tf_data.user_data = "$dumpvars";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 }
diff --git a/vpi/v2005_math.c b/vpi/v2005_math.c
index feda0818c..4183dd7d5 100644
--- a/vpi/v2005_math.c
+++ b/vpi/v2005_math.c
@@ -2,7 +2,7 @@
  *  Verilog-2005 math library for Icarus Verilog
  *  http://www.icarus.com/eda/verilog/
  *
- *  Copyright (C) 2007-2009  Cary R. (cygcary@yahoo.com)
+ *  Copyright (C) 2007-2010  Cary R. (cygcary@yahoo.com)
  *
  *  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
@@ -337,6 +337,7 @@ static void sys_v2005_math_register(void)
 {
     s_cb_data cb_data;
     s_vpi_systf_data tf_data;
+    vpiHandle res;
     unsigned idx;
 
     /* Register the single argument functions. */
@@ -349,7 +350,8 @@ static void sys_v2005_math_register(void)
     for (idx=0; va_single_data[idx].name != 0; idx++) {
         tf_data.tfname    = va_single_data[idx].name;
         tf_data.user_data = (PLI_BYTE8 *) &va_single_data[idx];
-        vpi_register_systf(&tf_data);
+        res = vpi_register_systf(&tf_data);
+        vpip_make_systf_system_defined(res);
     }
 
     /* Register the double argument functions. */
@@ -362,7 +364,8 @@ static void sys_v2005_math_register(void)
     for (idx=0; va_double_data[idx].name != 0; idx++) {
         tf_data.tfname    = va_double_data[idx].name;
         tf_data.user_data = (PLI_BYTE8 *) &va_double_data[idx];
-        vpi_register_systf(&tf_data);
+        res = vpi_register_systf(&tf_data);
+        vpip_make_systf_system_defined(res);
     }
 
     /* We need to clean up the userdata. */
diff --git a/vpi/va_math.c b/vpi/va_math.c
index cc2581422..0f5c05727 100644
--- a/vpi/va_math.c
+++ b/vpi/va_math.c
@@ -2,7 +2,7 @@
  *  Verilog-A math library for Icarus Verilog
  *  http://www.icarus.com/eda/verilog/
  *
- *  Copyright (C) 2007-2009  Cary R. (cygcary@yahoo.com)
+ *  Copyright (C) 2007-2010  Cary R. (cygcary@yahoo.com)
  *
  *  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
@@ -375,6 +375,7 @@ static void va_math_register(void)
 {
     s_cb_data cb_data;
     s_vpi_systf_data tf_data;
+    vpiHandle res;
     unsigned idx;
 
     /* Register the single argument functions. */
@@ -387,7 +388,8 @@ static void va_math_register(void)
     for (idx=0; va_single_data[idx].name != 0; idx++) {
         tf_data.tfname    = va_single_data[idx].name;
         tf_data.user_data = (PLI_BYTE8 *) &va_single_data[idx];
-        vpi_register_systf(&tf_data);
+        res = vpi_register_systf(&tf_data);
+        vpip_make_systf_system_defined(res);
     }
 
     /* Register the double argument functions. */
@@ -400,7 +402,8 @@ static void va_math_register(void)
     for (idx=0; va_double_data[idx].name != 0; idx++) {
         tf_data.tfname    = va_double_data[idx].name;
         tf_data.user_data = (PLI_BYTE8 *) &va_double_data[idx];
-        vpi_register_systf(&tf_data);
+        res = vpi_register_systf(&tf_data);
+        vpip_make_systf_system_defined(res);
     }
 
     /* We need to clean up the userdata. */
diff --git a/vpi/vams_simparam.c b/vpi/vams_simparam.c
index 87ac2e6f0..11779a8c1 100644
--- a/vpi/vams_simparam.c
+++ b/vpi/vams_simparam.c
@@ -1,5 +1,5 @@
 /*
- *  Copyright (C) 2008-2009  Cary R. (cygcary@yahoo.com)
+ *  Copyright (C) 2008-2010  Cary R. (cygcary@yahoo.com)
  *
  *  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
@@ -263,6 +263,7 @@ static PLI_INT32 simparam_str_sizetf(PLI_BYTE8 *name_ext)
 void vams_simparam_register(void)
 {
       s_vpi_systf_data tf_data;
+      vpiHandle res;
 
       tf_data.type        = vpiSysFunc;
       tf_data.sysfunctype = vpiRealFunc;
@@ -271,7 +272,8 @@ void vams_simparam_register(void)
       tf_data.sizetf      = 0;
       tf_data.tfname      = "$simparam";
       tf_data.user_data   = "";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 
       tf_data.type        = vpiSysFunc;
       tf_data.sysfunctype = vpiSizedFunc;  /* What should this be? */
@@ -280,5 +282,6 @@ void vams_simparam_register(void)
       tf_data.sizetf      = simparam_str_sizetf;  /* Only 128 characters! */
       tf_data.tfname      = "$simparam$str";
       tf_data.user_data   = "$str";
-      vpi_register_systf(&tf_data);
+      res = vpi_register_systf(&tf_data);
+      vpip_make_systf_system_defined(res);
 }
diff --git a/vpi_user.h b/vpi_user.h
index 27dcbce34..0122bfdac 100644
--- a/vpi_user.h
+++ b/vpi_user.h
@@ -594,6 +594,7 @@ extern DLLEXPORT void (*vlog_startup_routines[])();
 extern void vpip_format_strength(char*str, s_vpi_value*value, unsigned bit);
 extern void vpip_set_return_value(int value);
 extern s_vpi_vecval vpip_calc_clog2(vpiHandle arg);
+extern void vpip_make_systf_system_defined(vpiHandle ref);
 
 EXTERN_C_END
 
diff --git a/vvp/vpi_priv.cc b/vvp/vpi_priv.cc
index 28c7d0cbe..daf4a2bb6 100644
--- a/vvp/vpi_priv.cc
+++ b/vvp/vpi_priv.cc
@@ -151,7 +151,12 @@ PLI_INT32 vpi_chk_error(p_vpi_error_info info)
 
 PLI_INT32 vpi_compare_objects(vpiHandle obj1, vpiHandle obj2)
 {
-      assert(0);
+      assert(obj1);
+      assert(obj2);
+
+	// Does this actually work for all cases?
+      if (obj1 != obj2) return 0;
+      else return 1;
 }
 
 /*
@@ -173,8 +178,8 @@ void vpi_get_systf_info(vpiHandle ref, p_vpi_systf_data data)
  	    struct __vpiSysTaskCall*call = (struct __vpiSysTaskCall*)ref;
  	    rfp = call->defn;
       }
-	/* Assert that vpiUserDefn is true! For now this is always true. */
-      assert(1);
+	/* Assert that vpiUserDefn is true! */
+      assert(rfp->is_user_defn);
 
       data->type = rfp->info.type;
       data->sysfunctype = rfp->info.sysfunctype;
@@ -1006,6 +1011,8 @@ static vpiHandle vpi_iterate_global(int type)
 	  case vpiModule:
 	    return vpip_make_root_iterator();
 
+	  case vpiUserSystf:
+	    return vpip_make_systf_iterator();
       }
 
       return 0;
diff --git a/vvp/vpi_priv.h b/vvp/vpi_priv.h
index 7f705004b..bb80078b7 100644
--- a/vvp/vpi_priv.h
+++ b/vvp/vpi_priv.h
@@ -417,8 +417,11 @@ extern struct __vpiRealVar* vpip_realvar_from_handle(vpiHandle obj);
 struct __vpiUserSystf {
       struct __vpiHandle base;
       s_vpi_systf_data info;
+      bool is_user_defn;
 };
 
+extern vpiHandle vpip_make_systf_iterator(void);
+
 extern struct __vpiUserSystf* vpip_find_systf(const char*name);
 
 
diff --git a/vvp/vpi_tasks.cc b/vvp/vpi_tasks.cc
index 0ed434826..3c4906c86 100644
--- a/vvp/vpi_tasks.cc
+++ b/vvp/vpi_tasks.cc
@@ -59,7 +59,7 @@ static vpiHandle systask_handle(int type, vpiHandle ref)
 
 	  case vpiUserSystf:
 	      /* Assert that vpiUserDefn is true! */
-	    assert(1);
+	    assert(rfp->defn->is_user_defn);
 	    return &rfp->defn->base;
 
 	  default:
@@ -86,9 +86,8 @@ static int systask_get(int type, vpiHandle ref)
 	  case vpiLineNo:
 	    return rfp->lineno;
 
-	    /* For now we always have this information. */
 	  case vpiUserDefn:
-	    return 1;
+	    return rfp->defn->is_user_defn;
 
 	  default:
 	    return vpiUndefined;
@@ -109,9 +108,8 @@ static int sysfunc_get(int type, vpiHandle ref)
 	  case vpiLineNo:
 	    return rfp->lineno;
 
-	    /* For now we always have this information. */
 	  case vpiUserDefn:
-	    return 1;
+	    return rfp->defn->is_user_defn;
 
 	  default:
 	    return vpiUndefined;
@@ -544,6 +542,74 @@ void def_table_delete(void)
 }
 #endif
 
+struct __vpiSystfIterator {
+      struct __vpiHandle base;
+      unsigned next;
+};
+
+static vpiHandle systf_iterator_scan(vpiHandle ref, int)
+{
+      assert(ref->vpi_type->type_code == vpiIterator);
+      struct __vpiSystfIterator*obj = (struct __vpiSystfIterator*) ref;
+
+      if (obj->next >= def_count) {
+	    vpi_free_object(ref);
+	    return 0;
+      }
+
+      unsigned use_index = obj->next;
+      while (!def_table[use_index]->is_user_defn) {
+	    obj->next += 1;
+	    use_index = obj->next;
+	    if (obj->next >= def_count) {
+		  vpi_free_object(ref);
+		  return 0;
+	    }
+      }
+      obj->next += 1;
+      return &(def_table[use_index])->base;
+}
+
+static int systf_iterator_free_object(vpiHandle ref)
+{
+      assert(ref->vpi_type->type_code == vpiIterator);
+      struct __vpiSystfIterator*obj = (struct __vpiSystfIterator*) ref;
+      free(obj);
+      return 1;
+}
+
+static const struct __vpirt vpip_systf_iterator_rt = {
+      vpiIterator,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      systf_iterator_scan,
+      systf_iterator_free_object
+};
+
+vpiHandle vpip_make_systf_iterator(void)
+{
+	/* Check to see if there are any user defined functions. */
+      bool have_user_defn = false;
+      unsigned idx;
+      for (idx = 0; idx < def_count; idx += 1) {
+	    if (def_table[idx]->is_user_defn) {
+		  have_user_defn = true;
+		  break;
+	    }
+      }
+      if (!have_user_defn) return 0;
+
+      struct __vpiSystfIterator*res;
+      res = (struct __vpiSystfIterator*) calloc(1, sizeof (*res));
+      res->base.vpi_type = &vpip_systf_iterator_rt;
+      res->next = idx;
+      return &res->base;
+}
+
 struct __vpiUserSystf* vpip_find_systf(const char*name)
 {
       for (unsigned idx = 0 ;  idx < def_count ;  idx += 1)
@@ -553,6 +619,14 @@ struct __vpiUserSystf* vpip_find_systf(const char*name)
       return 0;
 }
 
+void vpip_make_systf_system_defined(vpiHandle ref)
+{
+      assert(ref);
+      assert(ref->vpi_type->type_code == vpiUserSystf);
+      struct __vpiUserSystf*obj = (__vpiUserSystf*) ref;
+      obj->is_user_defn = false;
+}
+
 /*
  * A vpi_call is actually built up into a vpiSysTaskCall VPI object
  * that refers back to the vpiUserSystf VPI object that is the
@@ -742,6 +816,7 @@ vpiHandle vpi_register_systf(const struct t_vpi_systf_data*ss)
 
       cur->info = *ss;
       cur->info.tfname = strdup(ss->tfname);
+      cur->is_user_defn = true;
 
       return &cur->base;
 }
diff --git a/vvp/vvp.def b/vvp/vvp.def
index b0f334339..ba44435e7 100644
--- a/vvp/vvp.def
+++ b/vvp/vvp.def
@@ -37,6 +37,7 @@ vpi_sim_control
 vpi_sim_vcontrol
 vpi_vprintf
 
-vpip_format_strength
-vpip_set_return_value
 vpip_calc_clog2
+vpip_format_strength
+vpip_make_systf_system_defined
+vpip_set_return_value