Add error on missing pure virtual functions (#4961).

Changes

@@ -20,6 +20,7 @@ Verilator 5.023 devel
 **Minor:**
 
 * Add DFG 'regularize' pass, and improve variable removal (#4937). [Geza Lore]
+* Add error on missing pure virtual functions (#4961).
 * Add error on calling static function without object (#4962).
 * Support public packed struct / union (#860) (#4878). [Kefa Chen]
 * Change installation to be relocatable (#4927). [Geza Lore]

src/V3AstNodes.cpp

@@ -2449,6 +2449,7 @@ void AstNodeFTask::dump(std::ostream& str) const {
     if (dpiOpenChild()) str << " [DPIOPENCHILD]";
     if (dpiOpenParent()) str << " [DPIOPENPARENT]";
     if (prototype()) str << " [PROTOTYPE]";
+    if (pureVirtual()) str << " [PUREVIRTUAL]";
     if (recursive()) str << " [RECURSIVE]";
     if (taskPublic()) str << " [PUBLIC]";
     if ((dpiImport() || dpiExport()) && cname() != name()) str << " [c=" << cname() << "]";

src/V3LinkDot.cpp

@@ -2214,20 +2214,25 @@ class LinkDotResolveVisitor final : public VNVisitor {
         return classSymp;
     }
     void importImplementsClass(AstClass* implementsClassp, VSymEnt* interfaceSymp,
-                               AstClass* interfaceClassp) {
+                               AstClass* baseClassp) {
-        UINFO(8, "importImplementsClass to " << implementsClassp << " from " << interfaceClassp
+        // Also used for standard 'extends' from a base class
-                                             << endl);
+        UINFO(8,
+              "importImplementsClass to " << implementsClassp << " from " << baseClassp << endl);
         for (VSymEnt::const_iterator it = interfaceSymp->begin(); it != interfaceSymp->end();
              ++it) {
             if (AstNode* interfaceSubp = it->second->nodep()) {
                 UINFO(8, "  SymFunc " << interfaceSubp << endl);
                 if (VN_IS(interfaceSubp, NodeFTask)) {
                     const VSymEnt* const foundp = m_curSymp->findIdFlat(interfaceSubp->name());
+                    const AstNodeFTask* const interfaceFuncp = VN_CAST(interfaceSubp, NodeFTask);
+                    if (!interfaceFuncp || !interfaceFuncp->pureVirtual()) continue;
                     bool existsInChild = foundp && !foundp->imported();
+                    const string impOrExtends
+                        = baseClassp->isInterfaceClass() ? " implements " : " extends ";
                     if (!existsInChild && !implementsClassp->isInterfaceClass()) {
                         implementsClassp->v3error(
-                            "Class " << implementsClassp->prettyNameQ() << " implements "
+                            "Class " << implementsClassp->prettyNameQ() << impOrExtends
-                                     << interfaceClassp->prettyNameQ()
+                                     << baseClassp->prettyNameQ()
                                      << " but is missing implementation for "
                                      << interfaceSubp->prettyNameQ() << " (IEEE 1800-2023 8.26)\n"
                                      << implementsClassp->warnContextPrimary() << '\n'
@@ -2239,8 +2244,8 @@ class LinkDotResolveVisitor final : public VNVisitor {
                     if (!existsInChild && it != m_ifClassImpNames.end()
                         && it->second != interfaceSubp) {  // Not exact same function from diamond
                         implementsClassp->v3error(
-                            "Class " << implementsClassp->prettyNameQ() << " implements "
+                            "Class " << implementsClassp->prettyNameQ() << impOrExtends
-                                     << interfaceClassp->prettyNameQ()
+                                     << baseClassp->prettyNameQ()
                                      << " but missing inheritance conflict resolution for "
                                      << interfaceSubp->prettyNameQ()
                                      << " (IEEE 1800-2023 8.26.6.2)\n"
@@ -2257,7 +2262,7 @@ class LinkDotResolveVisitor final : public VNVisitor {
     void importSymbolsFromExtended(AstClass* const nodep, AstClassExtends* const cextp) {
         AstClass* const baseClassp = cextp->classp();
         VSymEnt* const srcp = m_statep->getNodeSym(baseClassp);
-        if (baseClassp->isInterfaceClass()) importImplementsClass(nodep, srcp, baseClassp);
+        importImplementsClass(nodep, srcp, baseClassp);
         if (!cextp->isImplements()) m_curSymp->importFromClass(m_statep->symsp(), srcp);
     }
     void classExtendImport(AstClass* nodep) {

test_regress/t/t_class_mispure_bad.out

@@ -0,0 +1,7 @@
+%Error: t/t_class_mispure_bad.v:11:1: Class 'Bar' extends 'Base' but is missing implementation for 'pvfunc' (IEEE 1800-2023 8.26)
+   11 | class Bar extends Base;
+      | ^~~~~
+        t/t_class_mispure_bad.v:8:31: ... Location of interface class's function
+    8 |    pure virtual function void pvfunc();
+      |                               ^~~~~~
+%Error: Exiting due to

test_regress/t/t_class_mispure_bad.pl

@@ -0,0 +1,19 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2010 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(linter => 1);
+
+lint(
+    fails => 1,
+    expect_filename => $Self->{golden_filename},
+    );
+
+ok(1);
+1;

test_regress/t/t_class_mispure_bad.v

@@ -0,0 +1,21 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2024 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+virtual class Base;
+   pure virtual function void pvfunc();
+endclass
+
+class Bar extends Base;
+   // Bad, no implementation of pvfunc
+endclass
+
+module t;
+   initial begin
+      Bar obj = new();
+      obj.pvfunc();
+      $stop;
+   end
+endmodule