diff --git a/ci/ci-install.bash b/ci/ci-install.bash
index 594d96ba4..7ecc860de 100755
--- a/ci/ci-install.bash
+++ b/ci/ci-install.bash
@@ -55,16 +55,16 @@ if [ "$CI_BUILD_STAGE_NAME" = "build" ]; then
     sudo apt-get update
     sudo apt-get install ccache help2man libfl-dev ||
     sudo apt-get install ccache help2man libfl-dev
-    if [ "$CI_RUNS_ON" != "ubuntu-22.04" ]; then
+    if [[ ! "$CI_RUNS_ON" =~ "ubuntu-22.04" ]]; then
       # Some conflict of libunwind verison on 22.04, can live without it for now
       sudo apt-get install libgoogle-perftools-dev ||
       sudo apt-get install libgoogle-perftools-dev
     fi
-    if [ "$CI_RUNS_ON" = "ubuntu-20.04" ] || [ "$CI_RUNS_ON" = "ubuntu-22.04" ] || [ "$CI_RUNS_ON" = "ubuntu-24.04" ]; then
+    if [[ "$CI_RUNS_ON" =~ "ubuntu-20.04" ]] || [[ "$CI_RUNS_ON" =~ "ubuntu-22.04" ]] || [[ "$CI_RUNS_ON" =~ "ubuntu-24.04" ]]; then
       sudo apt-get install libsystemc libsystemc-dev ||
       sudo apt-get install libsystemc libsystemc-dev
     fi
-    if [ "$CI_RUNS_ON" = "ubuntu-22.04" ] || [ "$CI_RUNS_ON" = "ubuntu-24.04" ]; then
+    if [[ "$CI_RUNS_ON" =~ "ubuntu-22.04" ]] || [[ "$CI_RUNS_ON" =~ "ubuntu-24.04" ]]; then
       sudo apt-get install bear mold ||
       sudo apt-get install bear mold
     fi
@@ -92,11 +92,11 @@ elif [ "$CI_BUILD_STAGE_NAME" = "test" ]; then
     sudo apt-get install gdb gtkwave lcov libfl-dev ccache jq z3 ||
     sudo apt-get install gdb gtkwave lcov libfl-dev ccache jq z3
     # Required for test_regress/t/t_dist_attributes.py
-    if [ "$CI_RUNS_ON" = "ubuntu-22.04" ] || [ "$CI_RUNS_ON" = "ubuntu-24.04" ]; then
+    if [[ "$CI_RUNS_ON" =~ "ubuntu-22.04" ]] || [[ "$CI_RUNS_ON" =~ "ubuntu-24.04" ]]; then
       sudo apt-get install python3-clang mold ||
       sudo apt-get install python3-clang mold
     fi
-    if [ "$CI_RUNS_ON" = "ubuntu-20.04" ] || [ "$CI_RUNS_ON" = "ubuntu-22.04" ] || [ "$CI_RUNS_ON" = "ubuntu-24.04" ]; then
+    if [[ "$CI_RUNS_ON" =~ "ubuntu-20.04" ]] || [[ "$CI_RUNS_ON" =~ "ubuntu-22.04" ]] || [[ "$CI_RUNS_ON" =~ "ubuntu-24.04" ]]; then
       sudo apt-get install libsystemc-dev ||
       sudo apt-get install libsystemc-dev
     fi
diff --git a/ci/ci-script.bash b/ci/ci-script.bash
index 35b594422..88e6ff1dc 100755
--- a/ci/ci-script.bash
+++ b/ci/ci-script.bash
@@ -87,7 +87,7 @@ elif [ "$CI_BUILD_STAGE_NAME" = "test" ]; then
   fi
 
   # Run sanitize on Ubuntu 22.04 only
-  ( [ "$CI_RUNS_ON" = 'ubuntu-22.04' ] || [ "$CI_RUNS_ON" = 'ubuntu-24.04' ] ) && sanitize='--sanitize' || sanitize=''
+  ( [[ "$CI_RUNS_ON" =~ 'ubuntu-22.04' ]] || [[ "$CI_RUNS_ON" =~ 'ubuntu-24.04' ]] ) && sanitize='--sanitize' || sanitize=''
 
   TEST_REGRESS=test_regress
   if [ "$CI_RELOC" == 1 ]; then
@@ -121,10 +121,10 @@ elif [ "$CI_BUILD_STAGE_NAME" = "test" ]; then
       "$MAKE" -C "$TEST_REGRESS" SCENARIOS="--dist --vlt $sanitize" DRIVER_HASHSET=--hashset=3/4
       ;;
     vltmt-0)
-      "$MAKE" -C "$TEST_REGRESS" SCENARIOS=--vltmt DRIVER_HASHSET=--hashset=0/2
+      "$MAKE" -C "$TEST_REGRESS" SCENARIOS="--vltmt" DRIVER_HASHSET=--hashset=0/2
       ;;
     vltmt-1)
-      "$MAKE" -C "$TEST_REGRESS" SCENARIOS=--vltmt DRIVER_HASHSET=--hashset=1/2
+      "$MAKE" -C "$TEST_REGRESS" SCENARIOS="--vltmt" DRIVER_HASHSET=--hashset=1/2
       ;;
     coverage-all)
       nodist/code_coverage --stages 1-
diff --git a/include/verilated_vpi.cpp b/include/verilated_vpi.cpp
index 5ab3caca6..c05b0820d 100644
--- a/include/verilated_vpi.cpp
+++ b/include/verilated_vpi.cpp
@@ -2788,8 +2788,8 @@ vpiHandle vpi_put_value(vpiHandle object, p_vpi_value valuep, p_vpi_time /*time_
         } else if (valuep->format == vpiOctStrVal) {
             const int len = std::strlen(valuep->value.str);
             for (int i = 0; i < len; ++i) {
-                char digit = valuep->value.str[len - i - 1] - '0';
-                if (digit < 0 || digit > 7) {
+                unsigned char digit = valuep->value.str[len - i - 1] - '0';
+                if (digit > 7) {  // If str was < '0', then as unsigned, digit > 7
                     VL_VPI_WARNING_(__FILE__, __LINE__,
                                     "%s: Non octal character '%c' in '%s' as value %s for %s",
                                     __func__, digit + '0', valuep->value.str,
diff --git a/test_regress/t/t_a5_attributes_include.py b/test_regress/t/t_a5_attributes_include.py
index 730a6d447..5959677ae 100755
--- a/test_regress/t/t_a5_attributes_include.py
+++ b/test_regress/t/t_a5_attributes_include.py
@@ -30,7 +30,7 @@ if 'VERILATOR_TEST_NO_ATTRIBUTES' in os.environ:
 if not os.path.exists(root + "/src/obj_dbg/compile_commands.json"):
     test.skip("compile_commands.json not found. Please install 'bear > 3.0' and rebuild Verilator")
 if not have_clang_check():
-    test.skip("No libclang installed\n")
+    test.skip("No libclang installed")
 
 # some of the files are only used in Verilation
 # and are only in "include" folder
diff --git a/test_regress/t/t_a5_attributes_src.py b/test_regress/t/t_a5_attributes_src.py
index 3c55ea4e2..185d8eb46 100755
--- a/test_regress/t/t_a5_attributes_src.py
+++ b/test_regress/t/t_a5_attributes_src.py
@@ -30,7 +30,7 @@ if 'VERILATOR_TEST_NO_ATTRIBUTES' in os.environ:
 if not os.path.exists(root + "/src/obj_dbg/compile_commands.json"):
     test.skip("compile_commands.json not found. Please install 'bear > 3.0' and rebuild Verilator")
 if not have_clang_check():
-    test.skip("No libclang installed\n")
+    test.skip("No libclang installed")
 
 # some of the files are only used in Verilation
 # and are only in "include" folder
diff --git a/test_regress/t/t_dist_attributes_bad.py b/test_regress/t/t_dist_attributes_bad.py
index 14b04ec27..1fca2d090 100755
--- a/test_regress/t/t_dist_attributes_bad.py
+++ b/test_regress/t/t_dist_attributes_bad.py
@@ -30,7 +30,7 @@ if 'VERILATOR_TEST_NO_ATTRIBUTES' in os.environ:
 if not os.path.exists(root + "/.git"):
     test.skip("Not in a git repository")
 if not have_clang_check():
-    test.skip("No libclang installed\n")
+    test.skip("No libclang installed")
 
 aroot = os.path.abspath(root)
 ccjson_file = test.obj_dir + "/compile_commands.json"
diff --git a/test_regress/t/t_leak.py b/test_regress/t/t_leak.py
index a743e049c..cd84c8163 100755
--- a/test_regress/t/t_leak.py
+++ b/test_regress/t/t_leak.py
@@ -11,9 +11,6 @@ import vltest_bootstrap
 
 test.scenarios('vlt_all')
 
-if test.vltmt and test.getenv_def('TRAVIS_DIST', "None") == "trusty":
-    test.skip("Multithreaded test does not work under CI w/ Ubuntu Trusty")
-
 test.compile(make_top_shell=False,
              make_main=False,
              verilator_flags2=["--exe", test.pli_filename],
diff --git a/test_regress/t/t_math_real.v b/test_regress/t/t_math_real.v
index 5e2344e5b..6c6ac73e0 100644
--- a/test_regress/t/t_math_real.v
+++ b/test_regress/t/t_math_real.v
@@ -166,9 +166,11 @@ module t (/*AUTOARG*/
       `checks(s, "-inf");
       r = $sqrt(-1.0);  // NaN
       s = $sformatf("%g", r);
-      `checks(s, "-nan");
+      if (s == "-nan") s = "nan";
+      `checks(s, "nan");
       r = -$sqrt(-1.0);  // NaN
       s = $sformatf("%g", r);
+      if (s == "-nan") s = "nan";
       `checks(s, "nan");
 
       if (real'(TWENTY) != 20.0) $stop;
diff --git a/test_regress/t/t_prof.py b/test_regress/t/t_prof.py
index f47b92805..e5ebf6147 100755
--- a/test_regress/t/t_prof.py
+++ b/test_regress/t/t_prof.py
@@ -8,9 +8,13 @@
 # SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
 
 import vltest_bootstrap
+import platform
 
 test.scenarios('vlt_all')
 
+if re.search(r'clang', test.cxx_version) and 'aarch64' in platform.processor():
+    test.skip("Known compiler profile issues on clang aarch64")
+
 test.compile(verilator_flags2=["--stats --prof-cfuncs +define+T_PROF"])
 
 # TODO below might no longer be required as configure checks for -pg
diff --git a/test_regress/t/t_prof_timing.py b/test_regress/t/t_prof_timing.py
index e06dc0024..59f233265 100755
--- a/test_regress/t/t_prof_timing.py
+++ b/test_regress/t/t_prof_timing.py
@@ -8,10 +8,14 @@
 # SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
 
 import vltest_bootstrap
+import platform
 
 test.scenarios('vlt_all')
 test.top_filename = "t/t_prof.v"
 
+if re.search(r'clang', test.cxx_version) and 'aarch64' in platform.processor():
+    test.skip("Known compiler profile issues on clang aarch64")
+
 # TODO below might no longer be required as configure checks for -pg
 if 'VERILATOR_TEST_NO_GPROF' in os.environ:
     test.skip("Skipping due to VERILATOR_TEST_NO_GPROF")
diff --git a/test_regress/t/t_vpi_time_cb_c.cpp b/test_regress/t/t_vpi_time_cb_c.cpp
index 8bbbb0a48..4f69d232c 100644
--- a/test_regress/t/t_vpi_time_cb_c.cpp
+++ b/test_regress/t/t_vpi_time_cb_c.cpp
@@ -113,7 +113,7 @@ extern "C" void dpii_init() {
     t_cb_data cb_data_n1, cb_data_n2, cb_data_n3;
     bzero(&cb_data_n1, sizeof(cb_data_n1));
     bzero(&cb_data_n2, sizeof(cb_data_n2));
-    bzero(&cb_data_n2, sizeof(cb_data_n3));
+    bzero(&cb_data_n3, sizeof(cb_data_n3));
     s_vpi_time t1, t2, t3;
 
     cb_data_n1.reason = cbAfterDelay;