diff --git a/driver/cflexor.lex b/driver/cflexor.lex
index 68447cdc7..4e85f42f2 100644
--- a/driver/cflexor.lex
+++ b/driver/cflexor.lex
@@ -4,7 +4,7 @@
 
 %{
 /*
- * Copyright (c) 2001-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2001-2024 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
@@ -222,7 +222,7 @@ static char* trim_trailing_white(char*text, int trim)
       return strdup(text);
 }
 
-int yywrap()
+int yywrap(void)
 {
       return 1;
 }
diff --git a/lexor.lex b/lexor.lex
index 4e93cb87b..5a77684f3 100644
--- a/lexor.lex
+++ b/lexor.lex
@@ -1446,7 +1446,7 @@ static void process_ucdrive(const char*txt)
       uc_drive = ucd;
 }
 
-int yywrap()
+int yywrap(void)
 {
       return 1;
 }
diff --git a/libveriuser/a_initialize.c b/libveriuser/a_initialize.c
index ef3ccc60a..7d2d242b0 100644
--- a/libveriuser/a_initialize.c
+++ b/libveriuser/a_initialize.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002 Michael Ruff (mruff at chiaro.com)
+ * Copyright (c) 2002-2024 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
@@ -21,7 +21,7 @@
 
 int acc_error_flag;
 
-int acc_initialize()
+int acc_initialize(void)
 {
       acc_error_flag = 0;
 
diff --git a/libveriuser/getsimtime.c b/libveriuser/getsimtime.c
index 8724cf6c7..9aebfd6f4 100644
--- a/libveriuser/getsimtime.c
+++ b/libveriuser/getsimtime.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002-2020 Michael Ruff (mruff at chiaro.com)
+ * Copyright (c) 2002-2024 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
@@ -217,7 +217,7 @@ PLI_INT32 tf_igettimeprecision(void*obj)
 }
 
 
-PLI_INT32 tf_gettimeunit()
+PLI_INT32 tf_gettimeunit(void)
 {
       vpiHandle hand = vpi_handle(vpiScope, cur_instance);
       return vpi_get(vpiTimeUnit, hand);
diff --git a/tgt-vlog95/event.c b/tgt-vlog95/event.c
index 7d05b750b..c9bc406cd 100644
--- a/tgt-vlog95/event.c
+++ b/tgt-vlog95/event.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2011-2021 Cary R. (cygcary@yahoo.com)
+ * Copyright (C) 2011-2024 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
@@ -23,7 +23,7 @@
 
 static unsigned need_ivl_top_module = 0;
 
-void emit_icarus_generated_top_module()
+void emit_icarus_generated_top_module(void)
 {
       if (need_ivl_top_module) {
 	    fprintf(vlog_out,
diff --git a/tgt-vlog95/logic_lpm.c b/tgt-vlog95/logic_lpm.c
index c32c95f1a..93c18c266 100644
--- a/tgt-vlog95/logic_lpm.c
+++ b/tgt-vlog95/logic_lpm.c
@@ -1580,7 +1580,7 @@ static unsigned need_latch_prim = 0;
  * simulate a synthesized D-FF, etc., but we don't want them to take the
  * ideas behind the primitive(s) and claim them as their own.
  */
-void emit_icarus_generated_udps()
+void emit_icarus_generated_udps(void)
 {
 	/* Emit the copyright information and LGPL note and then emit any
 	 * needed primitives. */
diff --git a/tgt-vlog95/scope.c b/tgt-vlog95/scope.c
index 590857a8b..20185ed82 100644
--- a/tgt-vlog95/scope.c
+++ b/tgt-vlog95/scope.c
@@ -1023,7 +1023,7 @@ static void add_scope_to_list(ivl_scope_t scope)
       scopes_emitted[num_scopes_emitted-1] = ivl_scope_tname(scope);
 }
 
-void free_emitted_scope_list()
+void free_emitted_scope_list(void)
 {
       free(scopes_emitted);
       scopes_emitted = 0;
diff --git a/tgt-vlog95/udp.c b/tgt-vlog95/udp.c
index b33fe0752..a623b5a68 100644
--- a/tgt-vlog95/udp.c
+++ b/tgt-vlog95/udp.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2011 Cary R. (cygcary@yahoo.com)
+ * Copyright (C) 2011-2024 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
@@ -246,7 +246,7 @@ void add_udp_to_list(ivl_udp_t udp)
       udps[num_udps-1] = udp;
 }
 
-void emit_udp_list()
+void emit_udp_list(void)
 {
       unsigned idx;
       for (idx = 0; idx < num_udps; idx += 1) {
diff --git a/tgt-vvp/eval_real.c b/tgt-vvp/eval_real.c
index 176d0bc67..ed006751a 100644
--- a/tgt-vvp/eval_real.c
+++ b/tgt-vvp/eval_real.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003-2020 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2003-2024 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
@@ -29,7 +29,7 @@
 
 static unsigned long word_alloc_mask = 0x0f;
 
-int allocate_word()
+int allocate_word(void)
 {
       int res = 4;
 
diff --git a/vvp/lexor.lex b/vvp/lexor.lex
index 1b59cc415..83f07d12b 100644
--- a/vvp/lexor.lex
+++ b/vvp/lexor.lex
@@ -326,7 +326,7 @@ static char* strdupnew(char const *str)
 
 %%
 
-int yywrap()
+int yywrap(void)
 {
       return -1;
 }
diff --git a/vvp/vpi_priv.h b/vvp/vpi_priv.h
index c7a3dc7d8..256584b13 100644
--- a/vvp/vpi_priv.h
+++ b/vvp/vpi_priv.h
@@ -1,7 +1,7 @@
 #ifndef IVL_vpi_priv_H
 #define IVL_vpi_priv_H
 /*
- * Copyright (c) 2001-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2001-2024 Stephen Williams (steve@icarus.com)
  * Copyright (c) 2016 CERN Michele Castellana (michele.castellana@cern.ch)
  *
  *    This source code is free software; you can redistribute it
@@ -968,9 +968,9 @@ struct __vpiBinaryConst : public __vpiHandle {
 
       vvp_vector4_t bits;
 	/* TRUE if this constant is signed. */
-      int signed_flag :1;
+      unsigned signed_flag :1;
 	/* TRUE if this constant has an explicit size (i.e. 19'h0 vs. 'h0) */
-      int sized_flag   :1;
+      unsigned sized_flag  :1;
 };
 
 vpiHandle vpip_make_binary_const(unsigned wid, const char*bits);