diff --git a/ivlpp/lexor.lex b/ivlpp/lexor.lex
index 4f3577e89..0dc93a8ed 100644
--- a/ivlpp/lexor.lex
+++ b/ivlpp/lexor.lex
@@ -44,7 +44,7 @@ static void  macro_start_args();
 static void  macro_add_to_arg();
 static void  macro_finish_arg();
 static void  do_expand(int use_args);
-static char* macro_name();
+static const char* macro_name();
 
 static void include_filename();
 static void do_include();
@@ -1201,7 +1201,7 @@ static int macro_needs_args(const char*text)
     }
 }
 
-static char* macro_name()
+static const char* macro_name()
 {
     return cur_macro ? cur_macro->name : "";
 }
diff --git a/ivlpp/main.c b/ivlpp/main.c
index f3433be08..7a8b4241d 100644
--- a/ivlpp/main.c
+++ b/ivlpp/main.c
@@ -126,12 +126,13 @@ static int flist_read_flags(const char*path)
 
 	    if (strcmp(cp,"D") == 0) {
 		  char*val = strchr(arg, '=');
-		  if (val)
+		  const char *valo = "1";
+		  if (val) {
 			*val++ = 0;
-		  else
-			val = "1";
+			valo = val;
+		  }
 
-		  define_macro(arg, val, 0, 0);
+		  define_macro(arg, valo, 0, 0);
 
 	    } else if (strcmp(cp,"I") == 0) {
 		  include_dir = realloc(include_dir,
diff --git a/main.cc b/main.cc
index 1370d2cb6..ff5ee6f48 100644
--- a/main.cc
+++ b/main.cc
@@ -543,7 +543,7 @@ static void read_iconfig_file(const char*ipath)
 	    }
 
 	    if (strcmp(buf, "basedir") == 0) {
-		  free((char *)basedir);
+		  free((void *)basedir);
 		  basedir = strdup(cp);
 
 	    } else if (strcmp(buf, "debug") == 0) {
@@ -620,7 +620,7 @@ static void read_iconfig_file(const char*ipath)
 		  flags["VPI_MODULE_LIST"] = vpi_module_list;
 
 	    } else if (strcmp(buf, "out") == 0) {
-		  free((char *)flags["-o"]);
+		  free((void *)flags["-o"]);
 		  flags["-o"] = strdup(cp);
 
 	    } else if (strcmp(buf, "sys_func") == 0) {
@@ -732,17 +732,17 @@ static void EOC_cleanup(void)
 
       for (list<const char*>::iterator suf = library_suff.begin() ;
            suf != library_suff.end() ; suf ++ ) {
-	    free((char *)*suf);
+	    free((void *)*suf);
       }
       library_suff.clear();
 
-      free((char *) basedir);
+      free((void *) basedir);
       free(ivlpp_string);
       free(depfile_name);
 
       for (map<string, const char*>::iterator flg = flags.begin() ;
            flg != flags.end() ; flg ++ ) {
-	    free((char *)flg->second);
+	    free((void *)flg->second);
       }
       flags.clear();
 
diff --git a/tgt-stub/stub.c b/tgt-stub/stub.c
index 2d6d0ed4a..acf2c215b 100644
--- a/tgt-stub/stub.c
+++ b/tgt-stub/stub.c
@@ -1533,7 +1533,7 @@ static void show_logic(ivl_net_logic_t net)
 static int show_scope(ivl_scope_t net, void*x)
 {
       unsigned idx;
-      char *is_auto;
+      const char *is_auto;
 
       fprintf(out, "scope: %s (%u parameters, %u signals, %u logic)",
 	      ivl_scope_name(net), ivl_scope_params(net),
diff --git a/tgt-vvp/eval_expr.c b/tgt-vvp/eval_expr.c
index 248b3df80..cf3847614 100644
--- a/tgt-vvp/eval_expr.c
+++ b/tgt-vvp/eval_expr.c
@@ -219,7 +219,7 @@ static void eval_logic_into_integer(ivl_expr_t expr, unsigned ix)
 		unsigned word = 0;
 		if (ivl_signal_dimensions(sig) > 0) {
 		      ivl_expr_t ixe;
-		      char*type = ivl_expr_signed(expr) ? "/s" : "";
+		      const char*type = ivl_expr_signed(expr) ? "/s" : "";
 
 			/* Detect the special case that this is a
 			   variable array. In this case, the ix/getv
@@ -246,7 +246,7 @@ static void eval_logic_into_integer(ivl_expr_t expr, unsigned ix)
 		            break;
 		      }
 		}
-		char*type = ivl_signal_signed(sig) ? "/s" : "";
+		const char*type = ivl_signal_signed(sig) ? "/s" : "";
 		fprintf(vvp_out, "    %%ix/getv%s %u, v%p_%u;\n", type, ix,
 		                 sig, word);
 		break;
diff --git a/tgt-vvp/eval_real.c b/tgt-vvp/eval_real.c
index b3fc68e71..eeb8abfc1 100644
--- a/tgt-vvp/eval_real.c
+++ b/tgt-vvp/eval_real.c
@@ -459,7 +459,7 @@ static int draw_unary_real(ivl_expr_t expr)
 
       if (ivl_expr_opcode(expr) == 'r') { /* Cast an integer value to a real. */
 	    struct vector_info res;
-	    char *suffix = "";
+	    const char *suffix = "";
 	    assert(ivl_expr_value(sube) != IVL_VT_REAL);
 	    res = draw_eval_expr(sube, 1);
 	    if (ivl_expr_signed(sube)) suffix = "/s";
diff --git a/tgt-vvp/vvp_process.c b/tgt-vvp/vvp_process.c
index 2bbaec015..5e12cc75d 100644
--- a/tgt-vvp/vvp_process.c
+++ b/tgt-vvp/vvp_process.c
@@ -772,7 +772,7 @@ static int show_stmt_assign_nb(ivl_statement_t net)
 
 	    if (cnt) {
 		  int count_index = allocate_word();
-		  char*type = ivl_expr_signed(cnt) ? "/s" : "";
+		  const char*type = ivl_expr_signed(cnt) ? "/s" : "";
 		  draw_eval_expr_into_integer(cnt, count_index);
 		  fprintf(vvp_out, "    %%evctl%s %s, %d;\n", type, name,
 		                   count_index);
@@ -1683,7 +1683,7 @@ static int show_stmt_repeat(ivl_statement_t net, ivl_scope_t sscope)
       unsigned lab_top = local_count++, lab_out = local_count++;
       ivl_expr_t expr = ivl_stmt_cond_expr(net);
       struct vector_info cnt = draw_eval_expr(expr, 0);
-      char *sign = ivl_expr_signed(expr) ? "s" : "u";
+      const char *sign = ivl_expr_signed(expr) ? "s" : "u";
 
 	/* Test that 0 < expr */
       fprintf(vvp_out, "T_%u.%u %%cmp/%s 0, %u, %u;\n", thread_count,
diff --git a/vpi/lxt_write.c b/vpi/lxt_write.c
index 3ed778cc5..9731363e9 100644
--- a/vpi/lxt_write.c
+++ b/vpi/lxt_write.c
@@ -996,8 +996,8 @@ if(rgh) lt_recurse_dictionary_free(lt, rgh);
 
 static int lt_dictval_compare(const void *v1, const void *v2)
 {
-dslxt_Tree *s1 = *(dslxt_Tree **)v1;
-dslxt_Tree *s2 = *(dslxt_Tree **)v2;
+const dslxt_Tree *s1 = *(const dslxt_Tree * const *)v1;
+const dslxt_Tree *s2 = *(const dslxt_Tree * const *)v2;
 
 if(s1->val > s2->val) return(1); else return(-1);	/* they're *never* equal */
 }
diff --git a/vpi/sys_display.c b/vpi/sys_display.c
index bc7773033..b8b4a317b 100644
--- a/vpi/sys_display.c
+++ b/vpi/sys_display.c
@@ -878,6 +878,7 @@ static unsigned int get_numeric(char **rtn, struct strobe_cb_info *info,
 static char *get_display(unsigned int *rtnsz, struct strobe_cb_info *info)
 {
   char *result, *fmt, *rtn, *func_name;
+  const char *cresult;
   s_vpi_value value;
   unsigned int idx, size, width;
   char buf[256];
@@ -998,10 +999,10 @@ static char *get_display(unsigned int *rtnsz, struct strobe_cb_info *info)
         vpi_printf("WARNING: %s:%d: unknown argument type (%s) given to %s!\n",
                    info->filename, info->lineno, vpi_get_str(vpiType, item),
                    info->name);
-        result = "<?>";
-        width = strlen(result);
+        cresult = "<?>";
+        width = strlen(cresult);
         rtn = realloc(rtn, (size+width)*sizeof(char));
-        memcpy(rtn+size-1, result, width);
+        memcpy(rtn+size-1, cresult, width);
         break;
     }
     size += width;
@@ -1755,9 +1756,9 @@ static PLI_INT32 sys_timeformat_calltf(PLI_BYTE8*xx)
       return 0;
 }
 
-static char *pts_convert(int value)
+static const char *pts_convert(int value)
 {
-      char *string;
+      const char *string;
       switch (value) {
             case   0: string = "1s";    break;
             case  -1: string = "100ms"; break;
diff --git a/vpi/sys_priv.c b/vpi/sys_priv.c
index f6846e45b..a21af244f 100644
--- a/vpi/sys_priv.c
+++ b/vpi/sys_priv.c
@@ -102,7 +102,7 @@ char *get_filename(vpiHandle callh, char *name, vpiHandle file)
 }
 
 void check_for_extra_args(vpiHandle argv, vpiHandle callh, char *name,
-                          char *arg_str, unsigned opt)
+                          const char *arg_str, unsigned opt)
 {
 	/* Check that there are no extra arguments. */
       if (vpi_scan(argv) != 0) {
diff --git a/vpi/sys_priv.h b/vpi/sys_priv.h
index 3a13d1851..d375a2ae9 100644
--- a/vpi/sys_priv.h
+++ b/vpi/sys_priv.h
@@ -38,8 +38,8 @@ extern PLI_UINT64 timerec_to_time64(const struct t_vpi_time*timerec);
 extern char *as_escaped(char *arg);
 extern char *get_filename(vpiHandle callh, char *name, vpiHandle file);
 
-extern void check_for_extra_args(vpiHandle argv, vpiHandle callh,
-                                 char *name, char *arg_str, unsigned opt);
+extern void check_for_extra_args(vpiHandle argv, vpiHandle callh, char *name,
+                                 const char *arg_str, unsigned opt);
 
 struct timeformat_info_s {
       int units;
diff --git a/vpi/sys_table.c b/vpi/sys_table.c
index f7b1ad2be..637319e0f 100644
--- a/vpi/sys_table.c
+++ b/vpi/sys_table.c
@@ -59,7 +59,7 @@ static void sys_lxt_or_vcd_register()
       int idx;
       struct t_vpi_vlog_info vlog_info;
 
-      char*dumper;
+      const char*dumper;
 
 	/* Get the dumper of choice from the IVERILOG_DUMPER
 	   environment variable. */
diff --git a/vpi/sys_vcd.c b/vpi/sys_vcd.c
index 949ee3167..edcd2ee1d 100644
--- a/vpi/sys_vcd.c
+++ b/vpi/sys_vcd.c
@@ -708,7 +708,7 @@ static int draw_scope(vpiHandle item, vpiHandle callh)
 {
       int depth;
       const char *name;
-      char *type;
+      const char *type;
 
       vpiHandle scope = vpi_handle(vpiScope, item);
       if (!scope) return 0;