diff --git a/test_regress/driver.pl b/test_regress/driver.pl
index 6e10dd113..14053faa5 100755
--- a/test_regress/driver.pl
+++ b/test_regress/driver.pl
@@ -1724,7 +1724,7 @@ sub _make_main {
     }
     $fh->print("\n");
 
-    print $fh "    delete topp; topp=NULL;\n";
+    print $fh "    VL_DO_DANGLING(delete topp, topp);\n";
     print $fh "    exit(0L);\n";
     print $fh "}\n";
     $fh->close();
diff --git a/test_regress/t/t_clk_2in.cpp b/test_regress/t/t_clk_2in.cpp
index 0630be1a1..60d9c866e 100644
--- a/test_regress/t/t_clk_2in.cpp
+++ b/test_regress/t/t_clk_2in.cpp
@@ -8,7 +8,7 @@
 #include <verilated.h>
 #include VM_PREFIX_INCLUDE
 
-unsigned int main_time = false;
+unsigned int main_time = 0;
 
 double sc_time_stamp() { return main_time; }
 
diff --git a/test_regress/t/t_dpi_var.cpp b/test_regress/t/t_dpi_var.cpp
index 1f4f8b0a0..146ddafe0 100644
--- a/test_regress/t/t_dpi_var.cpp
+++ b/test_regress/t/t_dpi_var.cpp
@@ -114,7 +114,7 @@ void mon_eval() {
 
 //======================================================================
 
-unsigned int main_time = false;
+unsigned int main_time = 0;
 
 double sc_time_stamp() { return main_time; }
 int main(int argc, char** argv, char** env) {
diff --git a/test_regress/t/t_leak.cpp b/test_regress/t/t_leak.cpp
index 559a17ce8..83db456a1 100644
--- a/test_regress/t/t_leak.cpp
+++ b/test_regress/t/t_leak.cpp
@@ -12,7 +12,7 @@
 #include <verilated.h>
 #include "Vt_leak.h"
 
-unsigned int main_time = false;
+unsigned int main_time = 0;
 double sc_time_stamp() { return main_time; }
 
 long long get_memory_usage() {
diff --git a/test_regress/t/t_vpi_get.cpp b/test_regress/t/t_vpi_get.cpp
index e2ba788e8..0bed48be3 100644
--- a/test_regress/t/t_vpi_get.cpp
+++ b/test_regress/t/t_vpi_get.cpp
@@ -45,7 +45,7 @@ using namespace std;
 #define TEST_MSG \
     if (0) printf
 
-unsigned int main_time = false;
+unsigned int main_time = 0;
 
 //======================================================================
 
diff --git a/test_regress/t/t_vpi_memory.cpp b/test_regress/t/t_vpi_memory.cpp
index 2da149eb1..ef7829a1c 100644
--- a/test_regress/t/t_vpi_memory.cpp
+++ b/test_regress/t/t_vpi_memory.cpp
@@ -45,7 +45,7 @@ using namespace std;
 #define DEBUG \
     if (0) printf
 
-unsigned int main_time = false;
+unsigned int main_time = 0;
 
 //======================================================================
 
diff --git a/test_regress/t/t_vpi_module.cpp b/test_regress/t/t_vpi_module.cpp
index 81cfae35f..8b7322dcb 100644
--- a/test_regress/t/t_vpi_module.cpp
+++ b/test_regress/t/t_vpi_module.cpp
@@ -45,7 +45,7 @@ using namespace std;
 #define DEBUG \
     if (0) printf
 
-unsigned int main_time = false;
+unsigned int main_time = 0;
 
 #define CHECK_RESULT_NZ(got) \
     if (!(got)) { \
diff --git a/test_regress/t/t_vpi_time_cb.cpp b/test_regress/t/t_vpi_time_cb.cpp
index 7a831de1f..00a4d8443 100644
--- a/test_regress/t/t_vpi_time_cb.cpp
+++ b/test_regress/t/t_vpi_time_cb.cpp
@@ -43,7 +43,7 @@ using namespace std;
 #define TEST_MSG \
     if (0) printf
 
-unsigned int main_time = false;
+unsigned int main_time = 0;
 unsigned int callback_count_time1 = 3;
 unsigned int callback_count_time2 = 4;
 unsigned int callback_count_start_of_sim = 0;
diff --git a/test_regress/t/t_vpi_unimpl.cpp b/test_regress/t/t_vpi_unimpl.cpp
index 9e3f9621d..b8f82cdb4 100644
--- a/test_regress/t/t_vpi_unimpl.cpp
+++ b/test_regress/t/t_vpi_unimpl.cpp
@@ -32,8 +32,8 @@
 #define DEBUG \
     if (0) printf
 
-unsigned int main_time = false;
-unsigned int callback_count = false;
+unsigned int main_time = 0;
+unsigned int callback_count = 0;
 
 //======================================================================
 
diff --git a/test_regress/t/t_vpi_var.cpp b/test_regress/t/t_vpi_var.cpp
index 9f170cb9d..26d5deb89 100644
--- a/test_regress/t/t_vpi_var.cpp
+++ b/test_regress/t/t_vpi_var.cpp
@@ -45,11 +45,11 @@ using namespace std;
 #define TEST_MSG \
     if (0) printf
 
-unsigned int main_time = false;
-unsigned int callback_count = false;
-unsigned int callback_count_half = false;
-unsigned int callback_count_quad = false;
-unsigned int callback_count_strs = false;
+unsigned int main_time = 0;
+unsigned int callback_count = 0;
+unsigned int callback_count_half = 0;
+unsigned int callback_count_quad = 0;
+unsigned int callback_count_strs = 0;
 unsigned int callback_count_strs_max = 500;
 
 //======================================================================
diff --git a/test_regress/t/t_vpi_zero_time_cb.cpp b/test_regress/t/t_vpi_zero_time_cb.cpp
index 5694db5a4..10164ec87 100644
--- a/test_regress/t/t_vpi_zero_time_cb.cpp
+++ b/test_regress/t/t_vpi_zero_time_cb.cpp
@@ -43,7 +43,7 @@ using namespace std;
 #define TEST_MSG \
     if (0) printf
 
-unsigned int main_time = false;
+unsigned int main_time = 0;
 unsigned int callback_count_zero_time = 0;
 unsigned int callback_count_start_of_sim = 0;