diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index c28671bea..93c713ec2 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -96,7 +96,13 @@ jobs:
           - {os: ubuntu-24.04, compiler: {cc: gcc, cxx: g++}, reloc: 0, suite: dist-vlt-3}
           - {os: ubuntu-24.04, compiler: {cc: gcc, cxx: g++}, reloc: 0, suite: vltmt-0}
           - {os: ubuntu-24.04, compiler: {cc: gcc, cxx: g++}, reloc: 0, suite: vltmt-1}
-          # Ubuntu 24.04 Clang - has problems
+          # Ubuntu 24.04 Clang
+          - {os: ubuntu-24.04, compiler: {cc: clang, cxx: clang++}, reloc: 0, suite: dist-vlt-0}
+          - {os: ubuntu-24.04, compiler: {cc: clang, cxx: clang++}, reloc: 0, suite: dist-vlt-1}
+          - {os: ubuntu-24.04, compiler: {cc: clang, cxx: clang++}, reloc: 0, suite: dist-vlt-2}
+          - {os: ubuntu-24.04, compiler: {cc: clang, cxx: clang++}, reloc: 0, suite: dist-vlt-3}
+          - {os: ubuntu-24.04, compiler: {cc: clang, cxx: clang++}, reloc: 0, suite: vltmt-0}
+          - {os: ubuntu-24.04, compiler: {cc: clang, cxx: clang++}, reloc: 0, suite: vltmt-1}
           # Ubuntu 22.04 GCC
           - {os: ubuntu-22.04, compiler: {cc: gcc, cxx: g++}, reloc: 0, suite: dist-vlt-0}
           - {os: ubuntu-22.04, compiler: {cc: gcc, cxx: g++}, reloc: 0, suite: dist-vlt-1}
diff --git a/test_regress/driver.py b/test_regress/driver.py
index f9864103e..4180f8737 100755
--- a/test_regress/driver.py
+++ b/test_regress/driver.py
@@ -23,6 +23,8 @@ import time
 from functools import lru_cache  # Eventually use python 3.9's cache
 from pprint import pformat, pprint
 
+import distro
+
 if False:  # pylint: disable=using-constant-test
     pprint(pformat("Ignored"))  # Prevent unused warning
 
@@ -140,10 +142,10 @@ class Capabilities:
     @staticproperty
     def cxx_version() -> str:  # pylint: disable=no-method-argument
         if Capabilities._cached_cxx_version is None:
-            Capabilities._cached_cxx_version = VtOs.run_capture(os.environ['MAKE'] + " -C " +
-                                                                os.environ['TEST_REGRESS'] +
-                                                                " -f Makefile print-cxx-version",
-                                                                check=False)
+            Capabilities._cached_cxx_version = VtOs.run_capture(
+                os.environ['MAKE'] + " --silent -C " + os.environ['TEST_REGRESS'] +
+                " -f Makefile print-cxx-version",
+                check=False)
 
         return Capabilities._cached_cxx_version
 
@@ -449,7 +451,7 @@ class Runner:
         else:
             error_msg = test.errors if test.errors else test.errors_keep_going
             test.oprint("FAILED: " + error_msg)
-            makecmd = VtOs.getenv_def('VERILATOR_MAKE', os.environ['MAKE'] + "&&")
+            makecmd = VtOs.getenv_def('VERILATOR_MAKE', os.environ['MAKE'] + " &&")
             upperdir = 'test_regress/' if re.search(r'test_regress', os.getcwd()) else ''
             self.fail_msgs.append("\t#" + test.soprint("%Error: " + error_msg) + "\t\t" + makecmd +
                                   " " + upperdir + test.py_filename + ' ' +
@@ -1238,6 +1240,13 @@ class VlTest:
                 self.skip("Test requires Coroutines; ignore error since not available\n")
                 return
 
+            if self.timing and self.sc and re.search(r'Ubuntu 24.04', distro.name(
+                    pretty=True)) and re.search(r'clang', self.cxx_version):
+                self.skip(
+                    "Test requires SystemC and Coroutines; broken on Ubuntu 24.04 w/clang\n" +
+                    " OS=" + distro.name(pretty=True) + " CXX=" + self.cxx_version)
+                return
+
             if param['verilator_make_cmake'] and not self.have_cmake:
                 self.skip(
                     "Test requires CMake; ignore error since not available or version too old\n")
diff --git a/test_regress/t/t_timing_cmake.py b/test_regress/t/t_timing_cmake.py
index 01e454245..ec436bda4 100755
--- a/test_regress/t/t_timing_cmake.py
+++ b/test_regress/t/t_timing_cmake.py
@@ -17,6 +17,9 @@ if not test.have_coroutines:
 if not test.have_cmake:
     test.skip("cmake is not installed")
 
+if re.search(r'clang', test.cxx_version):
+    test.skip("Known clang bug on ubuntu-24.04")
+
 test.compile(verilator_flags2=["--timescale 10ns/1ns --main --timing"],
              verilator_make_gmake=False,
              verilator_make_cmake=True)
diff --git a/test_regress/t/t_vpi_multidim.cpp b/test_regress/t/t_vpi_multidim.cpp
index 5041703cf..8a2f155a0 100644
--- a/test_regress/t/t_vpi_multidim.cpp
+++ b/test_regress/t/t_vpi_multidim.cpp
@@ -27,6 +27,7 @@
 
 #endif
 
+#include <cassert>
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
@@ -207,7 +208,9 @@ void _arr_iter_check(const char* name, int wordSize, const int* lows) {
 
 void _arr_access_format_check(TestVpiHandle& reg_h, int wordSize, const int* lows,
                               const char* octVal_s, PLI_INT32 format) {
+    constexpr int MAX_SPANSIZE = 1024;
     const int spanSize = wordSize / 2;
+    assert(spanSize <= MAX_SPANSIZE);
     s_vpi_value value_in;
     s_vpi_value value_out;
     s_vpi_error_info e;
@@ -226,14 +229,14 @@ void _arr_access_format_check(TestVpiHandle& reg_h, int wordSize, const int* low
         TestVpiHandle subreg_h = vpi_handle_by_index(reg_h, lows[2] + i);
         TEST_CHECK_NZ(subreg_h);
 
-        char octSpan_s[spanSize / 3 + 1];
+        char octSpan_s[MAX_SPANSIZE / 3 + 1];
         strncpy(octSpan_s, &octVal_s[spanSize / 3 * (1 - i)], spanSize / 3);
         octSpan_s[spanSize / 3] = '\0';
 
         uint64_t intVal;
         t_vpi_vecval vecVal[2];
         sscanf(octSpan_s, "%" SCNo64, &intVal);
-        char strVal_s[spanSize + 1];  // max length of the string happens for binary
+        char strVal_s[MAX_SPANSIZE + 1];  // max length of the string happens for binary
 
         if (format == vpiIntVal) {
             value_in.value.integer = intVal;
@@ -257,7 +260,7 @@ void _arr_access_format_check(TestVpiHandle& reg_h, int wordSize, const int* low
             sprintf(strVal_s, "%0*" PRIx64, (spanSize + 3) / 4, intVal);
             value_in.value.str = strVal_s;
         } else if (format == vpiOctStrVal) {
-            sprintf(strVal_s, "%" PRIo64, intVal);
+            sprintf(strVal_s, "%0*" PRIo64, (spanSize + 2) / 3, intVal);
             value_in.value.str = strVal_s;
         } else if (format == vpiStringVal) {
             const int byteCount = (spanSize + 7) / 8;
@@ -305,17 +308,13 @@ void _arr_access_check(const char* name, int wordSize, const int* lows) {
     std::uniform_int_distribution<uint64_t> rand64(std::numeric_limits<uint64_t>::min(),
                                                    std::numeric_limits<uint64_t>::max());
 
-    char octVal_s[wordSize / 3 + 1];
+    constexpr int MAX_WORDSIZE = 128;
+    assert(wordSize <= MAX_WORDSIZE);
+    char octVal_s[MAX_WORDSIZE / 3 + 2];
 
-    // fill octVal_s with random octal digits
-    if (wordSize < 64) {
-        sprintf(octVal_s, "%0*" PRIo64, wordSize / 3,
-                rand64(rng) % (static_cast<uint64_t>(1) << wordSize));
-    } else {
-        sprintf(octVal_s, "%0*" PRIo64, 63 / 3, rand64(rng));
-        sprintf(octVal_s + 63 / 3, "%0*" PRIo64, (wordSize - 63) / 3,
-                rand64(rng) % (static_cast<uint64_t>(1) << (wordSize - 63)));
-    }
+    octVal_s[0] = '0' + (rand64(rng) % (1ULL << ((((wordSize - 1) % 3) + 1))));
+    for (int i = 1; i < (wordSize + 2) / 3; ++i) octVal_s[i] = '0' + (rand64(rng) % 8);
+    octVal_s[(wordSize + 2) / 3] = '\0';
 
     // Assume that reading/writing to the "flattened" packed register is already tested,
     // check only reading/writing to sub-regs and validate the flattened result.