diff --git a/src/V3LanguageWords.h b/src/V3LanguageWords.h
index a11a6a222..907095605 100644
--- a/src/V3LanguageWords.h
+++ b/src/V3LanguageWords.h
@@ -48,7 +48,7 @@ public:
 
 private:
     static Singleton& s() {
-        static Singleton s_s;
+        static Singleton s_s;  // LCOV_EXCL_BR_LINE
         return s_s;
     }
 };
diff --git a/src/V3PreLex.l b/src/V3PreLex.l
index d706fc07c..aa331c629 100644
--- a/src/V3PreLex.l
+++ b/src/V3PreLex.l
@@ -595,11 +595,11 @@ string V3PreLex::cleanDbgStrg(const string& in) {
 }
 
 void V3PreLex::unused() {
-    if (0) {
+    if (VL_UNCOVERABLE(false)) {  // LCOV_EXCL_START
         // Prevent unused warnings
         yy_top_state();
         yyerror((char*)"");
-    }
+    }  // LCOV_EXCL_STOP
 }
 
 /*###################################################################
diff --git a/src/Verilator.cpp b/src/Verilator.cpp
index 39d51bb70..16fd4c94e 100644
--- a/src/Verilator.cpp
+++ b/src/Verilator.cpp
@@ -549,9 +549,9 @@ static void verilate(const string& argString) {
     }
     // Undocumented debugging - cannot be a switch as then command line
     // would mismatch forcing non-identicalness when we set it
-    if (!V3Os::getenvStr("VERILATOR_DEBUG_SKIP_IDENTICAL", "").empty()) {
+    if (!V3Os::getenvStr("VERILATOR_DEBUG_SKIP_IDENTICAL", "").empty()) {  // LCOV_EXCL_START
         v3fatalSrc("VERILATOR_DEBUG_SKIP_IDENTICAL w/ --skip-identical: Changes found\n");
-    }
+    }  // LCOV_EXCL_STOP
 
     //--FRONTEND------------------
 
diff --git a/test_regress/t/t_cover_lib.pl b/test_regress/t/t_cover_lib.pl
new file mode 100755
index 000000000..9d7305ac5
--- /dev/null
+++ b/test_regress/t/t_cover_lib.pl
@@ -0,0 +1,31 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2003 by Wilson Snyder. This program is free software; you
+# can redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+scenarios(vlt => 1);
+
+compile(
+    v_flags2 => ["--coverage t/t_cover_lib_c.cpp"],
+    verilator_flags2 => ["--exe -Wall -Wno-DECLFILENAME"],
+    make_flags => 'CPPFLAGS_ADD=-DTEST_OBJ_DIR="'.$Self->{obj_dir}.'"',
+    make_top_shell => 0,
+    make_main => 0,
+    );
+
+execute(
+    check_finished => 1,
+    );
+
+files_identical_sorted("$Self->{obj_dir}/coverage1.dat", "t/t_cover_lib_1.out");
+files_identical_sorted("$Self->{obj_dir}/coverage2.dat", "t/t_cover_lib_2.out");
+files_identical_sorted("$Self->{obj_dir}/coverage3.dat", "t/t_cover_lib_3.out");
+files_identical_sorted("$Self->{obj_dir}/coverage4.dat", "t/t_cover_lib_4.out");
+
+ok(1);
+1;
diff --git a/test_regress/t/t_cover_lib.v b/test_regress/t/t_cover_lib.v
new file mode 100644
index 000000000..1d95829b9
--- /dev/null
+++ b/test_regress/t/t_cover_lib.v
@@ -0,0 +1,10 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// Copyright 2017 by Wilson Snyder. This program is free software; you can
+// redistribute it and/or modify it under the terms of either the GNU
+// Lesser General Public License Version 3 or the Perl Artistic License
+// Version 2.0.
+// SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+module t (/*AUTOARG*/);
+endmodule
diff --git a/test_regress/t/t_cover_lib_1.out b/test_regress/t/t_cover_lib_1.out
new file mode 100644
index 000000000..d757bf25a
--- /dev/null
+++ b/test_regress/t/t_cover_lib_1.out
@@ -0,0 +1,4 @@
+# SystemC::Coverage-3
+C '
f../../t/t_cover_lib_c.cpp
l44
pagesp_user/t_cover_lib_c
okept_one
hmain' 100
+C '
f../../t/t_cover_lib_c.cpp
l45
pagesp_user/t_cover_lib_c
okept_two
hmain' 210
+C '
f../../t/t_cover_lib_c.cpp
l46
pagesp_user/t_cover_lib_c
olost_three
hmain' 220
diff --git a/test_regress/t/t_cover_lib_2.out b/test_regress/t/t_cover_lib_2.out
new file mode 100644
index 000000000..42ec9a18e
--- /dev/null
+++ b/test_regress/t/t_cover_lib_2.out
@@ -0,0 +1,3 @@
+# SystemC::Coverage-3
+C '
f../../t/t_cover_lib_c.cpp
l44
pagesp_user/t_cover_lib_c
okept_one
hmain' 100
+C '
f../../t/t_cover_lib_c.cpp
l45
pagesp_user/t_cover_lib_c
okept_two
hmain' 210
diff --git a/test_regress/t/t_cover_lib_3.out b/test_regress/t/t_cover_lib_3.out
new file mode 100644
index 000000000..78bddf206
--- /dev/null
+++ b/test_regress/t/t_cover_lib_3.out
@@ -0,0 +1,3 @@
+# SystemC::Coverage-3
+C '
f../../t/t_cover_lib_c.cpp
l44
pagesp_user/t_cover_lib_c
okept_one
hmain' 0
+C '
f../../t/t_cover_lib_c.cpp
l45
pagesp_user/t_cover_lib_c
okept_two
hmain' 0
diff --git a/test_regress/t/t_cover_lib_4.out b/test_regress/t/t_cover_lib_4.out
new file mode 100644
index 000000000..8b8f255e5
--- /dev/null
+++ b/test_regress/t/t_cover_lib_4.out
@@ -0,0 +1 @@
+# SystemC::Coverage-3
diff --git a/test_regress/t/t_cover_lib_c.cpp b/test_regress/t/t_cover_lib_c.cpp
new file mode 100644
index 000000000..8b288fad9
--- /dev/null
+++ b/test_regress/t/t_cover_lib_c.cpp
@@ -0,0 +1,62 @@
+// -*- mode: C++; c-file-style: "cc-mode" -*-
+//*************************************************************************
+//
+// Copyright 2009-2017 by Wilson Snyder. This program is free software; you can
+// redistribute it and/or modify it under the terms of either the GNU
+// Lesser General Public License Version 3 or the Perl Artistic License
+// Version 2.0.
+// SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+//
+//*************************************************************************
+
+#include <cstdio>
+#include <cstring>
+#include <iostream>
+#include "svdpi.h"
+
+#include "verilated_cov.h"
+
+#include VM_PREFIX_INCLUDE
+
+double sc_time_stamp() { return 0; }
+
+//======================================================================
+
+int failure = 0;
+
+#define CHECK_RESULT_HEX(got, exp) \
+    do { \
+        if ((got) != (exp)) { \
+            std::cout << std::dec << "%Error: " << __FILE__ << ":" << __LINE__ << std::hex \
+                      << ": GOT=" << (got) << "   EXP=" << (exp) << std::endl; \
+            failure = __LINE__; \
+        } \
+    } while (0)
+
+//======================================================================
+
+const char* name() { return "main"; }
+
+int main() {
+    vluint32_t covers[1];
+    vluint64_t coverw[2];
+
+    VL_COVER_INSERT(&covers[0], "comment", "kept_one");
+    VL_COVER_INSERT(&coverw[0], "comment", "kept_two");
+    VL_COVER_INSERT(&coverw[1], "comment", "lost_three");
+
+    covers[0] = 100;
+    coverw[0] = 210;
+    coverw[1] = 220;
+
+    VerilatedCov::write(VL_STRINGIFY(TEST_OBJ_DIR) "/coverage1.dat");
+    VerilatedCov::clearNonMatch("kept_");
+    VerilatedCov::write(VL_STRINGIFY(TEST_OBJ_DIR) "/coverage2.dat");
+    VerilatedCov::zero();
+    VerilatedCov::write(VL_STRINGIFY(TEST_OBJ_DIR) "/coverage3.dat");
+    VerilatedCov::clear();
+    VerilatedCov::write(VL_STRINGIFY(TEST_OBJ_DIR) "/coverage4.dat");
+
+    printf("*-* All Finished *-*\n");
+    exit(failure ? 10 : 0);
+}
diff --git a/test_regress/t/t_debug_emitv.out b/test_regress/t/t_debug_emitv.out
index 39df56002..72286aad6 100644
--- a/test_regress/t/t_debug_emitv.out
+++ b/test_regress/t/t_debug_emitv.out
@@ -78,6 +78,8 @@ module Vt_debug_emitv;
         end
         t.sum = __Vfunc_t.sub.f__3__Vfuncout;
         $display("[%0t] sum = %~", $timet.sum, t.sum);
+        $display("a?= $d%d", ($c(32'sh1) ? $c(32'sh14)
+                               : $c(32'sh1e)));
         $c(;);
         $display("%d", $c(0));
         $fopen(72'h2f6465762f6e756c6c);
@@ -165,7 +167,9 @@ module Vt_debug_emitv;
         t.str = $sformatf("cyc=%~", t.cyc);
         ;
         $display("str = %@", t.str);
-        $display("[%t] [%^]", $time$realtime, $realtime);
+        $display("%% [%t] [%^] to=%o td=%d", $time$realtime
+                 $time$time, $realtime$time$time, $time
+                 $time, $time);
         $sscanf(40'h666f6f3d35, "foo=%d", t.i);
         ;
         if ((32'sh5 != t.i)) begin
diff --git a/test_regress/t/t_debug_emitv.v b/test_regress/t/t_debug_emitv.v
index 67aa6bca8..d1ae29ee0 100644
--- a/test_regress/t/t_debug_emitv.v
+++ b/test_regress/t/t_debug_emitv.v
@@ -87,6 +87,7 @@ module t (/*AUTOARG*/
       sub.inc(fo, sum);
       sum = sub.f(sum);
       $display("[%0t] sum = %d", $time, sum);
+      $display("a?= $d", $c(1) ? $c32(20) : $c32(30));
 
       $c(";");
       $display("%d", $c("0"));
@@ -136,7 +137,7 @@ module t (/*AUTOARG*/
 
       str = $sformatf("cyc=%d", cyc);
       $display("str = %s", str);
-      $display("[%t] [%t]", $time, $realtime);
+      $display("%% [%t] [%t] to=%o td=%d", $time, $realtime, $time, $time);
       $sscanf("foo=5", "foo=%d", i);
       if (i != 5) $stop;
    end
diff --git a/test_regress/t/t_dpi_context_c.cpp b/test_regress/t/t_dpi_context_c.cpp
index 3204c9bea..1447ab083 100644
--- a/test_regress/t/t_dpi_context_c.cpp
+++ b/test_regress/t/t_dpi_context_c.cpp
@@ -74,6 +74,7 @@ int dpic_line() {
         printf("%%Warning: svGetCallerInfo failed\n");
         return 0;
     }
+    if (svGetCallerInfo(nullptr, nullptr)) {}  // Check doesn't segflt
     return lineno;
 }
 
diff --git a/test_regress/t/t_dpi_export_context2_bad.cpp b/test_regress/t/t_dpi_export_context2_bad.cpp
index b71f678d7..77ce4668c 100644
--- a/test_regress/t/t_dpi_export_context2_bad.cpp
+++ b/test_regress/t/t_dpi_export_context2_bad.cpp
@@ -30,6 +30,15 @@ int main(int argc, char* argv[]) {
     return 1;
 }
 int dpii_task() {
+
+    // Check DPI warnings
+    svScope scope = svGetScope();  // Will warn
+    if (scope) {}  // Unused
+    const char* filenamep = "";
+    int lineno = 0;
+    svGetCallerInfo(&filenamep, &lineno);  // Will warn
+    if (filenamep && lineno) {}  // Unused
+
     dpix_task();
     return 0;
 }
diff --git a/test_regress/t/t_dpi_export_context2_bad.out b/test_regress/t/t_dpi_export_context2_bad.out
index dc2091af3..c01b0dec6 100644
--- a/test_regress/t/t_dpi_export_context2_bad.out
+++ b/test_regress/t/t_dpi_export_context2_bad.out
@@ -1,2 +1,4 @@
+%Warning: DPI C Function called by Verilog DPI import with missing 'context' keyword.
+%Warning: DPI C Function called by Verilog DPI import with missing 'context' keyword.
 %Error: unknown:0: Testbench C called 'dpix_task' but scope wasn't set, perhaps due to dpi import call without 'context', or missing svSetScope. See IEEE 1800-2017 35.5.3.
 Aborting...
diff --git a/test_regress/t/t_dpi_import_c.cpp b/test_regress/t/t_dpi_import_c.cpp
index ebcbedef1..5a174cd67 100644
--- a/test_regress/t/t_dpi_import_c.cpp
+++ b/test_regress/t/t_dpi_import_c.cpp
@@ -189,7 +189,9 @@ int dpii_t_void() { return svIsDisabledState(); }
 int dpii_t_void_context() { return svIsDisabledState(); }
 int dpii_t_int(int i, int* o) {
     *o = i;
-    return svIsDisabledState();  // Tasks generally need this
+    bool disabled = svIsDisabledState();  // Tasks generally need this
+    svAckDisabledState();
+    return disabled;
 }
 #endif
 
diff --git a/test_regress/t/t_dpi_lib_c.cpp b/test_regress/t/t_dpi_lib_c.cpp
index bb214c594..b800b17fc 100644
--- a/test_regress/t/t_dpi_lib_c.cpp
+++ b/test_regress/t/t_dpi_lib_c.cpp
@@ -74,14 +74,32 @@ void dpii_lib_bit_check() {
     CHECK_RESULT_HEX(bv[1], 0xa7a6a5ad);
     CHECK_RESULT_HEX(bv[2], 0xabaaa9a8);
 
-    svBitVecVal btmp[1];
+    svBitVecVal btmp[2];
     svGetPartselBit(btmp, bv, 40, 8);
     CHECK_RESULT_HEX(btmp[0], 0xa5);
+    svGetPartselBit(btmp, bv, 32, 32);
+    CHECK_RESULT_HEX(btmp[0], 0xa7a6a5ad);
+    svGetPartselBit(btmp, bv, 48, 40);
+    CHECK_RESULT_HEX(btmp[0], 0xa9a8a7a6);
+    CHECK_RESULT_HEX(btmp[1], 0xaa);
 
+    btmp[0] = 0xa5;
     svPutPartselBit(bv, btmp[0], 48, 8);
     CHECK_RESULT_HEX(bv[0], 0xa3a2a1a0);
     CHECK_RESULT_HEX(bv[1], 0xa7a5a5ad);
     CHECK_RESULT_HEX(bv[2], 0xabaaa9a8);
+
+    btmp[0] = 0x11223344;
+    svPutPartselBit(bv, btmp[0], 32, 32);
+    CHECK_RESULT_HEX(bv[0], 0xa3a2a1a0);
+    CHECK_RESULT_HEX(bv[1], 0x11223344);
+    CHECK_RESULT_HEX(bv[2], 0xabaaa9a8);
+
+    btmp[0] = 0x99887766;
+    svPutPartselBit(bv, btmp[0], 24, 24);
+    CHECK_RESULT_HEX(bv[0], 0x66a2a1a0);
+    CHECK_RESULT_HEX(bv[1], 0x11228877);
+    CHECK_RESULT_HEX(bv[2], 0xabaaa9a8);
 }
 
 void dpii_lib_logic_check() {
@@ -112,11 +130,21 @@ void dpii_lib_logic_check() {
     CHECK_RESULT_HEX(lv[1].bval, 0xc7c6c5c8);
     CHECK_RESULT_HEX(lv[2].bval, 0xcbcac9c8);
 
-    svLogicVecVal ltmp[1];
+    svLogicVecVal ltmp[2];
     svGetPartselLogic(ltmp, lv, 40, 8);
     CHECK_RESULT_HEX(ltmp[0].aval, 0xb5);
     CHECK_RESULT_HEX(ltmp[0].bval, 0xc5);
+    svGetPartselLogic(ltmp, lv, 32, 32);
+    CHECK_RESULT_HEX(ltmp[0].aval, 0xb7b6b5bd);
+    CHECK_RESULT_HEX(ltmp[0].bval, 0xc7c6c5c8);
+    svGetPartselLogic(ltmp, lv, 48, 40);
+    CHECK_RESULT_HEX(ltmp[0].aval, 0xb9b8b7b6);
+    CHECK_RESULT_HEX(ltmp[0].bval, 0xc9c8c7c6);
+    CHECK_RESULT_HEX(ltmp[1].aval, 0xba);
+    CHECK_RESULT_HEX(ltmp[1].bval, 0xca);
 
+    ltmp[0].aval = 0xb5;
+    ltmp[0].bval = 0xc5;
     svPutPartselLogic(lv, ltmp[0], 48, 8);
     CHECK_RESULT_HEX(lv[0].aval, 0xb3b2b1b0);
     CHECK_RESULT_HEX(lv[1].aval, 0xb7b5b5bd);
@@ -124,6 +152,26 @@ void dpii_lib_logic_check() {
     CHECK_RESULT_HEX(lv[0].bval, 0xc3c2c1c0);
     CHECK_RESULT_HEX(lv[1].bval, 0xc7c5c5c8);
     CHECK_RESULT_HEX(lv[2].bval, 0xcbcac9c8);
+
+    ltmp[0].aval = 0x11223344;
+    ltmp[0].bval = 0x81828384;
+    svPutPartselLogic(lv, ltmp[0], 32, 32);
+    CHECK_RESULT_HEX(lv[0].aval, 0xb3b2b1b0);
+    CHECK_RESULT_HEX(lv[1].aval, 0x11223344);
+    CHECK_RESULT_HEX(lv[2].aval, 0xbbbab9b8);
+    CHECK_RESULT_HEX(lv[0].bval, 0xc3c2c1c0);
+    CHECK_RESULT_HEX(lv[1].bval, 0x81828384);
+    CHECK_RESULT_HEX(lv[2].bval, 0xcbcac9c8);
+
+    ltmp[0].aval = 0x99887766;
+    ltmp[0].bval = 0x89888786;
+    svPutPartselLogic(lv, ltmp[0], 24, 24);
+    CHECK_RESULT_HEX(lv[0].aval, 0x66b2b1b0);
+    CHECK_RESULT_HEX(lv[1].aval, 0x11228877);
+    CHECK_RESULT_HEX(lv[2].aval, 0xbbbab9b8);
+    CHECK_RESULT_HEX(lv[0].bval, 0x86c2c1c0);
+    CHECK_RESULT_HEX(lv[1].bval, 0x81828887);
+    CHECK_RESULT_HEX(lv[2].bval, 0xcbcac9c8);
 }
 
 //======================================================================
diff --git a/test_regress/t/t_vlcov_debugi.pl b/test_regress/t/t_vlcov_debugi.pl
index 8cc5f0d57..71b7b030c 100755
--- a/test_regress/t/t_vlcov_debugi.pl
+++ b/test_regress/t/t_vlcov_debugi.pl
@@ -17,6 +17,7 @@ foreach my $basename ("t_vlcov_data_a.dat",
     ) {
     run(cmd => ["../bin/verilator_coverage",
                 "t/${basename}",
+                "--debug",
                 "--debugi 9",
         ],
         tee => $Self->{verbose},
diff --git a/test_regress/t/t_vlcov_merge.pl b/test_regress/t/t_vlcov_merge.pl
index cfac15b48..bf62addf8 100755
--- a/test_regress/t/t_vlcov_merge.pl
+++ b/test_regress/t/t_vlcov_merge.pl
@@ -11,6 +11,7 @@ if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); di
 scenarios(dist => 1);
 
 run(cmd => ["../bin/verilator_coverage",
+            "--no-unlink", "--nounlink",
             "--write", "$Self->{obj_dir}/coverage.dat",
             "t/t_vlcov_data_a.dat",
             "t/t_vlcov_data_b.dat",
@@ -20,6 +21,10 @@ run(cmd => ["../bin/verilator_coverage",
     verilator_run => 1,
     );
 
+# Not deleted e.g. parsed --no-unlink properly
+files_identical("$Self->{t_dir}/t_vlcov_data_a.dat",
+                "$Self->{t_dir}/t_vlcov_data_a.dat");
+
 # Older clib's didn't properly sort maps, but the coverage data doesn't
 # really care about ordering. So avoid false failures by sorting.
 files_identical_sorted("$Self->{obj_dir}/coverage.dat", $Self->{golden_filename});
diff --git a/test_regress/t/t_vlcov_unlink.pl b/test_regress/t/t_vlcov_unlink.pl
new file mode 100755
index 000000000..51b2e7d0c
--- /dev/null
+++ b/test_regress/t/t_vlcov_unlink.pl
@@ -0,0 +1,32 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2003-2009 by Wilson Snyder. This program is free software; you
+# can redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+use File::Copy;
+
+scenarios(dist => 1);
+
+my $tmp = "$Self->{obj_dir}/copied.dat";
+File::Copy::copy("$Self->{t_dir}/t_vlcov_data_a.dat", $tmp);
+
+run(cmd => ["../bin/verilator_coverage",
+            "--unlink",
+            $tmp,
+            "--write", "$Self->{obj_dir}/output.dat"],
+    verilator_run => 1,
+    );
+
+files_identical("$Self->{obj_dir}/output.dat", "t/t_vlcov_data_a.dat");
+
+# --unlink should have removed it
+!-r $tmp or error("Not unlinked");
+
+ok(1);
+
+1;
diff --git a/test_regress/t/t_vpi_var.cpp b/test_regress/t/t_vpi_var.cpp
index 0b067dab6..205345bde 100644
--- a/test_regress/t/t_vpi_var.cpp
+++ b/test_regress/t/t_vpi_var.cpp
@@ -106,9 +106,15 @@ int _mon_check_mcd() {
     status = vpi_mcd_printf(mcd, (PLI_BYTE8*)"hello %s", "vpi_mcd_printf");
     CHECK_RESULT(status, strlen("hello vpi_mcd_printf"));
 
+    status = vpi_mcd_printf(0, (PLI_BYTE8*)"empty");
+    CHECK_RESULT(status, 0);
+
     status = vpi_mcd_flush(mcd);
     CHECK_RESULT(status, 0);
 
+    status = vpi_mcd_flush(0);
+    CHECK_RESULT(status, 1);
+
     status = vpi_mcd_close(mcd);
     // Icarus says 'error' on ones we're not using, so check only used ones return 0.
     CHECK_RESULT(status & mcd, 0);
@@ -421,6 +427,8 @@ int _mon_check_string() {
         vpi_get_value(vh1, &v);
         if (vpi_chk_error(&e)) { printf("%%vpi_chk_error : %s\n", e.message); }
 
+        (void)vpi_chk_error(nullptr);
+
         CHECK_RESULT_CSTR_STRIP(v.value.str, text_test_obs[i].initial);
 
         v.value.str = (PLI_BYTE8*)text_test_obs[i].value;