diff --git a/discipline.h b/discipline.h
index 9cfc4294b..0726710a9 100644
--- a/discipline.h
+++ b/discipline.h
@@ -1,7 +1,7 @@
 #ifndef __discipline_H
 #define __discipline_H
 /*
- * Copyright (c) 2008 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2008-2010 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
@@ -55,8 +55,8 @@ class ivl_discipline_s : public LineInfo {
 
       perm_string name() const         { return name_; }
       ivl_dis_domain_t domain() const  { return domain_; }
-      const ivl_nature_t potential() const { return potential_; }
-      const ivl_nature_t flow() const      { return flow_; }
+      ivl_nature_t potential() const { return potential_; }
+      ivl_nature_t flow() const      { return flow_; }
 
     private:
       perm_string name_;
diff --git a/tgt-vvp/draw_mux.c b/tgt-vvp/draw_mux.c
index 8e21c2f18..e5f9f4282 100644
--- a/tgt-vvp/draw_mux.c
+++ b/tgt-vvp/draw_mux.c
@@ -94,12 +94,13 @@ static void draw_lpm_mux_ab(ivl_lpm_t net, const char*muxz)
 
 static void draw_lpm_mux_nest(ivl_lpm_t net, const char*muxz)
 {
-      int idx, level;
+      unsigned idx, level;
       unsigned width = ivl_lpm_width(net);
       unsigned swidth = ivl_lpm_selects(net);
       char*select_input;
 
-      assert(ivl_lpm_size(net) == (1 << swidth));
+      assert(swidth < sizeof(unsigned));
+      assert(ivl_lpm_size(net) == (1U << swidth));
 
       select_input = strdup(draw_net_input(ivl_lpm_select(net)));
 
diff --git a/tgt-vvp/draw_net_input.c b/tgt-vvp/draw_net_input.c
index 2bd7aedb2..22e91d65c 100644
--- a/tgt-vvp/draw_net_input.c
+++ b/tgt-vvp/draw_net_input.c
@@ -93,7 +93,8 @@ static char* draw_C4_to_string(ivl_net_const_t cptr)
       for (idx = 0 ;  idx < ivl_const_width(cptr) ;  idx += 1) {
 	    char bitchar = bits[ivl_const_width(cptr)-idx-1];
 	    *dp++ = bitchar;
-	    assert((dp - result) < result_len);
+	    assert(dp >= result);
+	    assert((unsigned)(dp - result) < result_len);
       }
 
       strcpy(dp, ">");
@@ -143,7 +144,8 @@ static char* draw_C8_to_string(ivl_net_const_t cptr,
 		  assert(0);
 		  break;
 	    }
-	    assert(dp - result < nresult);
+	    assert(dp >= result);
+	    assert((unsigned)(dp - result) < nresult);
       }
 
       strcpy(dp, ">");
@@ -257,7 +259,8 @@ static char* draw_net_input_drive(ivl_nexus_t nex, ivl_nexus_ptr_t nptr)
 		  dp += ivl_logic_width(lptr);
 		  *dp++ = '>';
 		  *dp = 0;
-		  assert((dp-result) <= result_len);
+		  assert(dp >= result);
+		  assert((unsigned)(dp - result) <= result_len);
 		  return result;
 	    } else {
 		  char val[4];
@@ -276,7 +279,8 @@ static char* draw_net_input_drive(ivl_nexus_t nex, ivl_nexus_ptr_t nptr)
 		  dp += 3*ivl_logic_width(lptr);
 		  *dp++ = '>';
 		  *dp = 0;
-		  assert((dp-result) <= result_len);
+		  assert(dp >= result);
+		  assert((unsigned)(dp - result) <= result_len);
 		  return result;
 	    }
       }
@@ -292,7 +296,8 @@ static char* draw_net_input_drive(ivl_nexus_t nex, ivl_nexus_ptr_t nptr)
 		  dp += ivl_logic_width(lptr);
 		  *dp++ = '>';
 		  *dp = 0;
-		  assert((dp-result) <= result_len);
+		  assert(dp >= result);
+		  assert((unsigned)(dp - result) <= result_len);
 		  return result;
 	    } else {
 		  char val[4];
@@ -311,7 +316,8 @@ static char* draw_net_input_drive(ivl_nexus_t nex, ivl_nexus_ptr_t nptr)
 		  dp += 3*ivl_logic_width(lptr);
 		  *dp++ = '>';
 		  *dp = 0;
-		  assert((dp-result) <= result_len);
+		  assert(dp >= result);
+		  assert((unsigned)(dp - result) <= result_len);
 		  return result;
 	    }
       }
diff --git a/tgt-vvp/draw_ufunc.c b/tgt-vvp/draw_ufunc.c
index 1b30e9039..8e0f8fcfa 100644
--- a/tgt-vvp/draw_ufunc.c
+++ b/tgt-vvp/draw_ufunc.c
@@ -156,7 +156,7 @@ int draw_ufunc_real(ivl_expr_t expr)
       ivl_scope_t def = ivl_expr_def(expr);
       ivl_signal_t retval = ivl_scope_port(def, 0);
       int res = 0;
-      int idx;
+      unsigned idx;
 
         /* If this is an automatic function, allocate the local storage. */
       if (ivl_scope_is_auto(def)) {
diff --git a/tgt-vvp/draw_vpi.c b/tgt-vvp/draw_vpi.c
index 22ddabb9c..de0091b8e 100644
--- a/tgt-vvp/draw_vpi.c
+++ b/tgt-vvp/draw_vpi.c
@@ -308,7 +308,8 @@ static void draw_vpi_taskfunc_args(const char*call_string,
 			for (bit = wid ;  bit > 0 ;  bit -= 1)
 			      *dp++ = bits[bit-1];
 			*dp++ = 0;
-			assert(dp - buffer <= sizeof buffer);
+			assert(dp >= buffer);
+			assert((unsigned)(dp - buffer) <= sizeof buffer);
 		  }
 		  args[idx].text = strdup(buffer);
 		  continue;
diff --git a/tgt-vvp/eval_expr.c b/tgt-vvp/eval_expr.c
index 48e703dd5..4a73e9d8b 100644
--- a/tgt-vvp/eval_expr.c
+++ b/tgt-vvp/eval_expr.c
@@ -929,9 +929,9 @@ static struct vector_info draw_binary_expr_le(ivl_expr_t expr,
 	  case 'G':
 	    rv = draw_eval_expr_wid(re, owid, STUFF_OK_XZ);
 	    if (number_is_immediate(le,16,0) && !number_is_unknown(le)) {
-		  unsigned imm = get_number_immediate(le);
+		  long imm = get_number_immediate(le);
 		  assert(imm >= 0);
-		  fprintf(vvp_out, "   %%cmpi/%c %u, %u, %u;\n", s_flag,
+		  fprintf(vvp_out, "   %%cmpi/%c %u, %ld, %u;\n", s_flag,
 			  rv.base, imm, rv.wid);
 	    } else {
 		  lv = draw_eval_expr_wid(le, owid, STUFF_OK_XZ);
@@ -945,9 +945,9 @@ static struct vector_info draw_binary_expr_le(ivl_expr_t expr,
 	  case 'L':
 	    lv = draw_eval_expr_wid(le, owid, STUFF_OK_XZ);
 	    if (number_is_immediate(re,16,0) && !number_is_unknown(re)) {
-		  unsigned imm = get_number_immediate(re);
+		  long imm = get_number_immediate(re);
 		  assert(imm >= 0);
-		  fprintf(vvp_out, "   %%cmpi/%c %u, %u, %u;\n", s_flag,
+		  fprintf(vvp_out, "   %%cmpi/%c %u, %ld, %u;\n", s_flag,
 			  lv.base, imm, lv.wid);
 	    } else {
 		  rv = draw_eval_expr_wid(re, owid, STUFF_OK_XZ);
@@ -961,9 +961,9 @@ static struct vector_info draw_binary_expr_le(ivl_expr_t expr,
 	  case '<':
 	    lv = draw_eval_expr_wid(le, owid, STUFF_OK_XZ);
 	    if (number_is_immediate(re,16,0) && !number_is_unknown(re)) {
-		  unsigned imm = get_number_immediate(re);
+		  long imm = get_number_immediate(re);
 		  assert(imm >= 0);
-		  fprintf(vvp_out, "   %%cmpi/%c %u, %u, %u;\n", s_flag,
+		  fprintf(vvp_out, "   %%cmpi/%c %u, %ld, %u;\n", s_flag,
 			  lv.base, imm, lv.wid);
 	    } else {
 		  rv = draw_eval_expr_wid(re, owid, STUFF_OK_XZ);
@@ -976,9 +976,9 @@ static struct vector_info draw_binary_expr_le(ivl_expr_t expr,
 	  case '>':
 	    rv = draw_eval_expr_wid(re, owid, STUFF_OK_XZ);
 	    if (number_is_immediate(le,16,0) && !number_is_unknown(le)) {
-		  unsigned imm = get_number_immediate(le);
+		  long imm = get_number_immediate(le);
 		  assert(imm >= 0);
-		  fprintf(vvp_out, "   %%cmpi/%c %u, %u, %u;\n", s_flag,
+		  fprintf(vvp_out, "   %%cmpi/%c %u, %ld, %u;\n", s_flag,
 			  rv.base, imm, rv.wid);
 	    } else {
 		  lv = draw_eval_expr_wid(le, owid, STUFF_OK_XZ);
diff --git a/tgt-vvp/modpath.c b/tgt-vvp/modpath.c
index c8fb45e28..15a270846 100644
--- a/tgt-vvp/modpath.c
+++ b/tgt-vvp/modpath.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2007-2008 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2007-2010 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
@@ -28,7 +28,7 @@
 
 static ivl_signal_t find_path_source_port(ivl_delaypath_t path)
 {
-      int idx;
+      unsigned idx;
       ivl_nexus_t nex = ivl_path_source(path);
 
       for (idx = 0 ;  idx < ivl_nexus_ptrs(nex) ;  idx += 1) {
diff --git a/tgt-vvp/vvp_scope.c b/tgt-vvp/vvp_scope.c
index eb3a200ef..588d74f20 100644
--- a/tgt-vvp/vvp_scope.c
+++ b/tgt-vvp/vvp_scope.c
@@ -814,14 +814,15 @@ static void draw_logic_in_scope(ivl_net_logic_t lptr)
 	/* Get all the input label that I will use for parameters to
 	   the functor that I create later. */
       ninp = ivl_logic_pins(lptr) - 1;
+      assert(ninp >= 0);
       input_strings = calloc(ninp, sizeof(char*));
-      for (pdx = 0 ;  pdx < ninp ;  pdx += 1)
+      for (pdx = 0 ;  pdx < (unsigned)ninp ;  pdx += 1)
 	    input_strings[pdx] = draw_net_input(ivl_logic_pin(lptr, pdx+1));
 
       level = 0;
       while (ninp) {
-	    int inst;
-	    for (inst = 0; inst < ninp; inst += 4) {
+	    unsigned inst;
+	    for (inst = 0; inst < (unsigned)ninp; inst += 4) {
 		  if (ninp > 4)
 			fprintf(vvp_out, "L_%p/%d/%d .functor %s %u",
 				lptr, level, inst, lcasc, vector_width);
@@ -834,7 +835,7 @@ static void draw_logic_in_scope(ivl_net_logic_t lptr)
 			      fprintf(vvp_out, " [%u %u]", str0, str1);
 
 		  }
-		  for (pdx = inst; pdx < ninp && pdx < inst+4 ; pdx += 1) {
+		  for (pdx = inst; pdx < (unsigned)ninp && pdx < inst+4 ; pdx += 1) {
 			if (level) {
 			      fprintf(vvp_out, ", L_%p/%d/%d",
 				      lptr, level - 1, pdx*4);
diff --git a/vpi/sys_display.c b/vpi/sys_display.c
index 20dacc4e8..cecb66df8 100644
--- a/vpi/sys_display.c
+++ b/vpi/sys_display.c
@@ -265,7 +265,8 @@ static unsigned int get_format_char(char **rtn, int ljust, int plus,
   unsigned int ini_size = 512;  /* The initial size of the buffer. */
 
   /* Make sure the width fits in the initial buffer. */
-  if (width+1 > ini_size) ini_size = width + 1;
+  assert(width >= -1);
+  if ((unsigned int)(width+1) > ini_size) ini_size = width + 1;
 
   /* The default return value is the full format. */
   result = malloc(ini_size*sizeof(char));
diff --git a/vpi/sys_fileio.c b/vpi/sys_fileio.c
index 3e26b9516..27412161d 100644
--- a/vpi/sys_fileio.c
+++ b/vpi/sys_fileio.c
@@ -546,7 +546,7 @@ static unsigned fread_word(FILE *fp, vpiHandle word,
 	 * my local vector. */
       val.format = vpiVectorVal;
       vpi_get_value(word, &val);
-      for (bidx = 0; bidx < words; bidx += 1) {
+      for (bidx = 0; (unsigned)bidx < words; bidx += 1) {
 	    vector[bidx].aval = val.value.vector[bidx].aval;
 	    vector[bidx].bval = val.value.vector[bidx].bval;
       }
@@ -683,9 +683,10 @@ static PLI_INT32 sys_fread_calltf(PLI_BYTE8*name)
       vector = calloc(words, sizeof(s_vpi_vecval));
       bpe = (width+7)/8;
 
+      assert(count >= 0);
       if (is_mem) {
 	    rtn = 0;
-	    for (idx = 0; idx < count; idx += 1) {
+	    for (idx = 0; idx < (unsigned)count; idx += 1) {
 		  vpiHandle word;
 		  word = vpi_handle_by_index(mem_reg, start+(signed)idx);
 		  rtn += fread_word(fp, word, words, bpe, vector);
diff --git a/vpi/sys_sdf.c b/vpi/sys_sdf.c
index c0d9a5f2b..038547877 100644
--- a/vpi/sys_sdf.c
+++ b/vpi/sys_sdf.c
@@ -70,7 +70,8 @@ void sdf_select_instance(const char*celltype, const char*cellinst)
       const char*src = cellinst;
       const char*dp;
       while ( (dp=strchr(src, '.')) ) {
-	    int len = dp - src;
+	    unsigned len = dp - src;
+	    assert(dp >= src);
 	    assert(len < sizeof buffer);
 	    strncpy(buffer, src, len);
 	    buffer[len] = 0;