code coverage cleanup

Signed-off-by: Matthew Ballance <matt.ballance@gmail.com>

include/verilated.cpp

@@ -3603,16 +3603,14 @@ void VerilatedContextImp::commandArgVl(const std::string& arg) {
             // and the run can be reproduced by passing +verilator+seed+<that_value>.
             if (u64 == 0) u64 = pickRandomSeed();
             randSeed(static_cast<int>(u64));
-        } else if (0
-                   == std::strncmp(arg.c_str(), "+verilator+vpi+",
-                                   std::strlen("+verilator+vpi+"))) {
+        } else if (commandArgVlString(arg, "+verilator+vpi+", str)) {
             // With --vpi the generated --main (vl_load_vpi_libs) consumes this, so accept
             // it silently here.  Without --vpi there is no loader, so warn it is ignored.
 #if !VM_VPI
             VL_WARN_MT(
                 "COMMAND_LINE", 0, "",
                 ("+verilator+vpi+ ignored: simulation was not compiled with --vpi '" + arg + "'")
-                    .c_str());
+                    .c_str());  // LCOV_EXCL_LINE  (gcov zeroes this wrapped continuation line)
 #endif
         } else if (arg == "+verilator+V") {
             VerilatedImp::versionDump();  // Someday more info too

test_regress/t/t_flag_main_vpi.py

@@ -32,7 +32,12 @@ else:
 # Run the generated binary; load the VPI library via the +verilator+vpi+ plusarg.
 # The VPI library's output (observed 'count' reaching MAX_TICKS, then end-of-sim) is
 # checked against the golden .out file.
-test.execute(all_run_flags=["+verilator+vpi+" + test.obj_dir + "/libvpi.so"],
+# Also pass a non-VPI plusarg (skipped by the loader's prefix check) and a bare
+# +verilator+vpi+ with an empty payload (skipped by the empty-arg check), so both
+# loader-skip branches are exercised alongside the real library load.
+test.execute(all_run_flags=[
+    "+othertest", "+verilator+vpi+", "+verilator+vpi+" + test.obj_dir + "/libvpi.so"
+],
              check_finished=True,
              expect_filename=test.golden_filename)