Support 1800-2023 class and function :initial, :extends, :final virtual overrides (#5025). (#5025)

Changes

@@ -16,16 +16,18 @@ Verilator 5.023 devel
 * Add printing summary reports, use `--quiet` or `+verilator+quiet` to suppress (#4909).
 * Support 1800-2023 keywords, and parsing with UNDEFINED warnings.
 * Support 1800-2023 preprocessor ifdef expressions.
-* Support 1800-2023 DPI headers, svGetTime/svgGetTimeUnit/svGetTimePrecision methods.
 
 **Minor:**
 
+* Change 1800-2023 to be default language version.
 * Add DFG 'regularize' pass, and improve variable removal (#4937). [Geza Lore]
 * Add error when pass net to function argument (#4132) (#4966). [Fuad Ismail]
 * Add `UNUSEDLOOP` when unused loop is removed (#4926). [Bartłomiej Chmiel, Antmicro Ltd.]
 * Add custom version for verilator --version packaging (#4954). [Nolan Poe]
 * Add error on missing pure virtual functions (#4961).
 * Add error on calling static function without object (#4962).
+* Support 1800-2023 DPI headers, svGetTime/svgGetTimeUnit/svGetTimePrecision methods.
+* Support 1800-2023 class and function :initial, :extends, :final virtual overrides (#5025).
 * Support public packed struct / union (#860) (#4878). [Kefa Chen]
 * Support implicitly-typed variable definitions in for-loop initializers (#4945) (#4986). [Kevin Nygaard]
 * Improve installation to be relocatable (#4927). [Geza Lore]

src/V3Ast.h

@@ -242,6 +242,51 @@ inline std::ostream& operator<<(std::ostream& os, const VAccess& rhs) { return o
 
 // ######################################################################
 
+class VBaseOverride final {
+    bool m_extends : 1;
+    bool m_final : 1;
+    bool m_initial : 1;
+
+public:
+    VBaseOverride()
+        : m_extends{false}
+        , m_final{false}
+        , m_initial{false} {}
+    class Extends {};
+    VBaseOverride(Extends)
+        : m_extends{true}
+        , m_final{false}
+        , m_initial{false} {}
+    class Final {};
+    VBaseOverride(Final)
+        : m_extends{false}
+        , m_final{true}
+        , m_initial{false} {}
+    class Initial {};
+    VBaseOverride(Initial)
+        : m_extends{false}
+        , m_final{false}
+        , m_initial{true} {}
+    void combine(const VBaseOverride& other) {
+        m_extends |= other.m_extends;
+        m_final |= other.m_final;
+        m_initial |= other.m_initial;
+    }
+    bool isAny() const { return m_extends | m_final | m_initial; }
+    bool isExtends() const { return m_extends; }
+    bool isFinal() const { return m_final; }
+    bool isInitial() const { return m_initial; }
+    string ascii() const {
+        string out;
+        if (m_initial) out = VString::dot(out, " ", "initial");
+        if (m_extends) out = VString::dot(out, " ", "extends");
+        if (m_final) out = VString::dot(out, " ", "final");
+        return out;
+    }
+};
+
+// ######################################################################
+
 class VSigning final {
 public:
     enum en : uint8_t {

src/V3AstNodeOther.h

@@ -87,6 +87,7 @@ class AstNodeFTask VL_NOT_FINAL : public AstNode {
     bool m_underGenerate : 1;  // Under generate (for warning)
     bool m_virtual : 1;  // Virtual method in class
     bool m_needProcess : 1;  // Needs access to VlProcess of the caller
+    VBaseOverride m_baseOverride;  // BaseOverride (inital/final/extends)
     VLifetime m_lifetime;  // Default lifetime of local vars
     VIsCached m_purity;  // Pure state
 
@@ -183,6 +184,8 @@ public:
     bool isVirtual() const { return m_virtual; }
     void setNeedProcess() { m_needProcess = true; }
     bool needProcess() const { return m_needProcess; }
+    void baseOverride(const VBaseOverride& flag) { m_baseOverride = flag; }
+    VBaseOverride baseOverride() const { return m_baseOverride; }
     void lifetime(const VLifetime& flag) { m_lifetime = flag; }
     VLifetime lifetime() const { return m_lifetime; }
     bool isFirstInMyListOfStatements(AstNode* n) const override { return n == stmtsp(); }
@@ -2272,6 +2275,7 @@ class AstClass final : public AstNodeModule {
     // @astgen op4 := extendsp : List[AstClassExtends]
     // MEMBERS
     // @astgen ptr := m_classOrPackagep : Optional[AstClassPackage]  // Package to be emitted with
+    VBaseOverride m_baseOverride;  // BaseOverride (inital/final/extends)
     bool m_extended = false;  // Is extension or extended by other classes
     bool m_interfaceClass = false;  // Interface class
     bool m_needRNG = false;  // Need RNG, uses srandom/randomize
@@ -2307,6 +2311,8 @@ public:
     // Return true if this class is an extension of base class (SLOW)
     // Accepts nullptrs
     static bool isClassExtendedFrom(const AstClass* refClassp, const AstClass* baseClassp);
+    void baseOverride(const VBaseOverride& flag) { m_baseOverride = flag; }
+    VBaseOverride baseOverride() const { return m_baseOverride; }
     // Return the lowest class extended from, or this class
     AstClass* baseMostClassp();
     static bool isCacheableChild(const AstNode* nodep);

src/V3AstNodes.cpp

@@ -1539,6 +1539,7 @@ void AstClass::dumpJson(std::ostream& str) const {
     dumpJsonBoolFunc(str, isExtended);
     dumpJsonBoolFunc(str, isInterfaceClass);
     dumpJsonBoolFunc(str, isVirtual);
+    if (baseOverride().isAny()) dumpJsonStr(str, "baseOverride", baseOverride().ascii());
     dumpJsonGen(str);
 }
 void AstClassExtends::dump(std::ostream& str) const {
@@ -2488,6 +2489,7 @@ void AstNodeFTask::dumpJson(std::ostream& str) const {
     dumpJsonBoolFunc(str, prototype);
     dumpJsonBoolFunc(str, recursive);
     dumpJsonBoolFunc(str, taskPublic);
+    if (baseOverride().isAny()) dumpJsonStr(str, "baseOverride", baseOverride().ascii());
     dumpJsonStrFunc(str, cname);
     dumpJsonGen(str);
 }

src/V3ParseImp.h

@@ -103,6 +103,7 @@ struct V3ParseBisonYYSType final {
     FileLine* fl;
     AstNode* scp;  // Symbol table scope for future lookups
     int token;  // Read token, aka tok
+    VBaseOverride baseOverride;
     union {
         V3Number* nump;
         string* strp;

src/V3WidthCommit.cpp

@@ -27,6 +27,8 @@
 
 #include "V3WidthCommit.h"
 
+#include "V3MemberMap.h"
+
 VL_DEFINE_DEBUG_FUNCTIONS;
 
 //######################################################################
@@ -40,6 +42,7 @@ class WidthCommitVisitor final : public VNVisitor {
 
     // STATE
     AstNodeModule* m_modp = nullptr;
+    VMemberMap m_memberMap;  // Member names cached for fast lookup
 
 public:
     // METHODS
@@ -73,7 +76,7 @@ private:
         return nodep;
     }
     void classEncapCheck(AstNode* nodep, AstNode* defp, AstClass* defClassp) {
-        // Call on non-local class to check local/protected status and complain
+        // Check local/protected status and complain
         bool local = false;
         bool prot = false;
         if (const auto varp = VN_CAST(defp, Var)) {
@@ -110,10 +113,23 @@ private:
     // VISITORS
     void visit(AstNodeModule* nodep) override {
         VL_RESTORER(m_modp);
-        {
+        m_modp = nodep;
-            m_modp = nodep;
+        iterateChildren(nodep);
-            iterateChildren(nodep);
+        editDType(nodep);
-            editDType(nodep);
+        if (AstClass* const classp = VN_CAST(nodep, Class)) {
+            for (AstClassExtends* extendsp = classp->extendsp(); extendsp;
+                 extendsp = extendsp->classp()->extendsp()) {
+                const AstClass* const ebasep = extendsp->classp();
+                if (ebasep->baseOverride().isFinal()) {
+                    extendsp->v3error("Class " << nodep->prettyNameQ()
+                                               << " is being extended from class marked ':final'"
+                                                  " (IEEE 1800-2023 8.20)\n"
+                                               << extendsp->warnContextPrimary() << "\n"
+                                               << ebasep->warnOther()
+                                               << "... Location of ':final' class being extended\n"
+                                               << ebasep->warnContextSecondary());
+                }
+            }
         }
     }
     void visit(AstConst* nodep) override {
@@ -177,6 +193,45 @@ private:
             nodep->v3error(
                 "Illegal to have 'pure virtual' in non-virtual class (IEEE 1800-2023 8.21)");
         }
+        bool extended = false;
+        if (const AstClass* const classp = VN_CAST(m_modp, Class)) {
+            for (AstClassExtends* extendsp = classp->extendsp(); extendsp;
+                 extendsp = extendsp->classp()->extendsp()) {
+                const AstClass* const eclassp = extendsp->classp();
+                if (AstNodeFTask* const fbasep
+                    = VN_CAST(m_memberMap.findMember(eclassp, nodep->name()), NodeFTask)) {
+                    if (fbasep != nodep) {
+                        extended = true;
+                        if (nodep->baseOverride().isInitial()) {
+                            nodep->v3error("Member "
+                                           << nodep->prettyNameQ()
+                                           << " is marked ':initial' but is being extended"
+                                              " (IEEE 1800-2023 8.20)\n"
+                                           << nodep->warnContextPrimary() << "\n"
+                                           << fbasep->warnOther()
+                                           << "... Location of declaration being extended\n"
+                                           << fbasep->warnContextSecondary());
+                        }
+                        if (fbasep->baseOverride().isFinal()) {
+                            nodep->v3error(
+                                "Member "
+                                << nodep->prettyNameQ()
+                                << " is being extended from member marked ':final'"
+                                   " (IEEE 1800-2023 8.20)\n"
+                                << nodep->warnContextPrimary() << "\n"
+                                << fbasep->warnOther()
+                                << "... Location of ':final' declaration being extended\n"
+                                << fbasep->warnContextSecondary());
+                        }
+                    }
+                }
+            }
+        }
+        if (!extended && nodep->baseOverride().isExtends()) {
+            nodep->v3error("Member " << nodep->prettyNameQ()
+                                     << " marked ':extends' but no base class function is"
+                                        " being extend (IEEE 1800-2023 8.20)");
+        }
     }
     void visit(AstNodeVarRef* nodep) override {
         iterateChildren(nodep);

src/verilog.y

@@ -4458,6 +4458,7 @@ list_of_argumentsE<nodeExprp>:  // IEEE: [list_of_arguments]
 task_declaration<nodeFTaskp>:   // ==IEEE: task_declaration
                 yTASK dynamic_override_specifiersE lifetimeE taskId tfGuts yENDTASK endLabelE
                         { $$ = $4; $$->addStmtsp($5); SYMP->popScope($$);
+                          $$->baseOverride($2);
                           $$->lifetime($3);
                           GRAMMARP->endLabel($<fl>7, $$, $7); }
         ;
@@ -4472,11 +4473,13 @@ task_prototype<nodeFTaskp>:             // ==IEEE: task_prototype
 function_declaration<nodeFTaskp>:       // IEEE: function_declaration + function_body_declaration
                 yFUNCTION dynamic_override_specifiersE lifetimeE funcId funcIsolateE tfGuts yENDFUNCTION endLabelE
                         { $$ = $4; $4->attrIsolateAssign($5); $$->addStmtsp($6);
+                          $$->baseOverride($2);
                           $$->lifetime($3);
                           SYMP->popScope($$);
                           GRAMMARP->endLabel($<fl>8, $$, $8); }
         |       yFUNCTION dynamic_override_specifiersE lifetimeE funcIdNew funcIsolateE tfNewGuts yENDFUNCTION endLabelE
                         { $$ = $4; $4->attrIsolateAssign($5); $$->addStmtsp($6);
+                          $$->baseOverride($2);
                           $$->lifetime($3);
                           SYMP->popScope($$);
                           GRAMMARP->endLabel($<fl>8, $$, $8); }
@@ -7011,6 +7014,7 @@ classFront<classp>:             // IEEE: part of class_declaration
         //                      // IEEE 1800-2023: lifetimeE replaced with final_specifierE
                 classVirtualE yCLASS final_specifierE lifetimeE idAny/*class_identifier*/
                         { $$ = new AstClass{$2, *$5};
+                          $$->baseOverride($3);
                           $$->isVirtual($1);
                           SYMP->pushNew($<classp>$);
                           v3Global.setHasClasses(); }
@@ -7223,20 +7227,22 @@ class_method<nodep>:            // ==IEEE: class_method
                         { $$ = $3; $2.applyToNodes($3); $3->isExternProto(true); }
         ;
 
-dynamic_override_specifiersE:  // IEEE: dynamic_override_specifiers or empty
+dynamic_override_specifiersE<baseOverride>:  // IEEE: dynamic_override_specifiers or empty
-                /* empty */                             { /* UNSUP-2023-ignored */ }
+                /* empty */                             { $$ = VBaseOverride{}; }
         //                      // IEEE: Expanded [ initial_or_extends_specifier ] [ final_specifier ]
         //                      // Note lifetime used by members is instead under memberQual
-        |       ':' yINITIAL                            { /* UNSUP-2023-ignored */ }
+        |       ':' yINITIAL                            { $$ = VBaseOverride{VBaseOverride::Initial{}}; }
-        |       ':' yEXTENDS                            { /* UNSUP-2023-ignored */ }
+        |       ':' yEXTENDS                            { $$ = VBaseOverride{VBaseOverride::Extends{}}; }
-        |       ':' yINITIAL ':' yFINAL                 { /* UNSUP-2023-ignored */ }
+        |       ':' yINITIAL ':' yFINAL                 { $$ = VBaseOverride{VBaseOverride::Initial{}};
-        |       ':' yEXTENDS ':' yFINAL                 { /* UNSUP-2023-ignored */ }
+                                                          $$.combine(VBaseOverride{VBaseOverride::Final{}}); }
-        |       ':' yFINAL                              { /* UNSUP-2023-ignored */ }
+        |       ':' yEXTENDS ':' yFINAL                 { $$ = VBaseOverride{VBaseOverride::Extends{}};
+                                                          $$.combine(VBaseOverride{VBaseOverride::Final{}}); }
+        |       ':' yFINAL                              { $$ = VBaseOverride{VBaseOverride::Final{}}; }
         ;
 
-final_specifierE:  // ==IEEE: final_specifier (similar to dynamic_override_specifiers)
+final_specifierE<baseOverride>:  // ==IEEE: final_specifier (similar to dynamic_override_specifiers)
-                /* empty */                             { }
+                /* empty */                             { $$ = VBaseOverride{}; }
-        |       ':' yFINAL                              { /* UNSUP-2023-ignored */ }
+        |       ':' yFINAL                              { $$ = VBaseOverride{VBaseOverride::Final{}}; }
         ;
 
 // IEEE: class_constructor_prototype

test_regress/t/t_class_override.pl

@@ -0,0 +1,21 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2020 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(simulator => 1);
+
+compile(
+    );
+
+execute(
+    check_finished => 1,
+    );
+
+ok(1);
+1;

test_regress/t/t_class_override.v

@@ -0,0 +1,113 @@
+// 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
+
+// Function names correspond to how the function is declared in the base class,
+// then the extend class, with letters:
+//   Does-not-exist(x), Nothing(n), :initial(i), :extends(e), :final(f)
+
+class Base;
+   // _X = non-existant
+   // _n = None
+   function int get_n; return 1; endfunction
+   function int get_n_n; return 1; endfunction
+   function int get_n_e; return 1; endfunction
+   function int get_n_ef; return 1; endfunction
+   function int get_n_i; return 1; endfunction
+   function int get_n_if; return 1; endfunction
+   function int get_n_f; return 1; endfunction
+   // _e = :extends
+   // function :extends int get_e; return 1; endfunction  // Bad
+   // _ef = :extends :final
+   // function :extends :final int get_ef; return 1; endfunction  // Bad
+   // _i = :initial
+   function :initial int get_i; return 1; endfunction
+   function :initial int get_i_n; return 1; endfunction
+   function :initial int get_i_e; return 1; endfunction
+   function :initial int get_i_ef; return 1; endfunction
+   function :initial int get_i_i; return 1; endfunction
+   function :initial int get_i_if; return 1; endfunction
+   function :initial int get_i_f; return 1; endfunction
+   // _if = :initial :final
+   function :initial :final int get_if; return 1; endfunction
+   function :initial :final int get_if_n; return 1; endfunction
+   function :initial :final int get_if_e; return 1; endfunction
+   function :initial :final int get_if_ef; return 1; endfunction
+   function :initial :final int get_if_i; return 1; endfunction
+   function :initial :final int get_if_if; return 1; endfunction
+   function :initial :final int get_if_f; return 1; endfunction
+   // _f = :final
+   function :final int get_f; return 1; endfunction
+   function :final int get_f_n; return 1; endfunction
+   function :final int get_f_e; return 1; endfunction
+   function :final int get_f_ef; return 1; endfunction
+   function :final int get_f_i; return 1; endfunction
+   function :final int get_f_if; return 1; endfunction
+   function :final int get_f_f; return 1; endfunction
+
+endclass
+
+class Cls extends Base;
+   // _X = non-existant
+   function int get_x_n; return 1; endfunction
+   // function :extends int get_x_e; return 1; endfunction  // Bad
+   // function :extends :final int get_x_ef; return 1; endfunction  // Bad
+   function :initial int get_x_i; return 1; endfunction
+   function :initial :final int get_x_if; return 1; endfunction
+   function :final int get_x_f; return 1; endfunction
+   // _n = None
+   function int get_n_n; return 1; endfunction
+   function :extends int get_n_e; return 1; endfunction
+   function :extends :final int get_n_ef; return 1; endfunction
+   // function :initial int get_n_i; return 1; endfunction  // Bad
+   // function :initial :final int get_n_if; return 1; endfunction  // Bad
+   function :final int get_n_f; return 1; endfunction
+   // _e = :extends
+   // _ef = :extends :final
+   // _i = :initial
+   function int get_i_n; return 1; endfunction
+   function :extends int get_i_e; return 1; endfunction
+   function :extends :final int get_i_ef; return 1; endfunction
+   // function :initial int get_i_i; return 1; endfunction  // Bad
+   // function :initial :final int get_i_if; return 1; endfunction  // Bad
+   function :final int get_i_f; return 1; endfunction
+   // _if = :initial :final
+   // function int get_if_n; return 1; endfunction  // Bad
+   // function :extends int get_if_e; return 1; endfunction  // Bad
+   // function :extends :final int get_if_ef; return 1; endfunction  // Bad
+   // function :initial int get_if_i; return 1; endfunction  // Bad
+   // function :initial :final int get_if_if; return 1; endfunction  // Bad
+   // function :final int get_if_f; return 1; endfunction  // Bad
+   // _f = :final
+   // function int get_f_n; return 1; endfunction  // Bad
+   // function :extends int get_f_e; return 1; endfunction  // Bad
+   // function :extends :final int get_f_ef; return 1; endfunction  // Bad
+   // function :initial int get_f_i; return 1; endfunction  // Bad
+   // function :initial :final int get_f_if; return 1; endfunction  // Bad
+   // function :final int get_f_f; return 1; endfunction  // Bad
+endclass
+
+class CBase;
+endclass
+
+class CClsN extends CBase;
+endclass
+
+class :final CClsF extends CBase;
+endclass
+
+module t (/*AUTOARG*/);
+   initial begin
+      Cls c;
+      CClsF cc;
+
+      if (c != null) $stop;
+      c = new;
+      cc = new;
+
+      $write("*-* All Finished *-*\n");
+      $finish;
+   end
+endmodule

test_regress/t/t_class_override_bad.out

@@ -0,0 +1,164 @@
+%Error: t/t_class_override_bad.v:22:26: Member 'get_e' marked ':extends' but no base class function is being extend (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   22 |    function :extends int get_e; return 1; endfunction   
+      |                          ^~~~~
+%Error: t/t_class_override_bad.v:24:33: Member 'get_ef' marked ':extends' but no base class function is being extend (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   24 |    function :extends :final int get_ef; return 1; endfunction   
+      |                                 ^~~~~~
+%Error: t/t_class_override_bad.v:55:26: Member 'get_x_e' marked ':extends' but no base class function is being extend (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   55 |    function :extends int get_x_e; return 1; endfunction   
+      |                          ^~~~~~~
+%Error: t/t_class_override_bad.v:56:33: Member 'get_x_ef' marked ':extends' but no base class function is being extend (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   56 |    function :extends :final int get_x_ef; return 1; endfunction   
+      |                                 ^~~~~~~~
+%Error: t/t_class_override_bad.v:64:26: Member 'get_n_i' is marked ':initial' but is being extended (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   64 |    function :initial int get_n_i; return 1; endfunction   
+      |                          ^~~~~~~
+        t/t_class_override_bad.v:18:17: ... Location of declaration being extended
+   18 |    function int get_n_i; return 1; endfunction
+      |                 ^~~~~~~
+%Error: t/t_class_override_bad.v:65:33: Member 'get_n_if' is marked ':initial' but is being extended (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   65 |    function :initial :final int get_n_if; return 1; endfunction   
+      |                                 ^~~~~~~~
+        t/t_class_override_bad.v:19:17: ... Location of declaration being extended
+   19 |    function int get_n_if; return 1; endfunction
+      |                 ^~~~~~~~
+%Error: t/t_class_override_bad.v:73:26: Member 'get_i_i' is marked ':initial' but is being extended (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   73 |    function :initial int get_i_i; return 1; endfunction   
+      |                          ^~~~~~~
+        t/t_class_override_bad.v:30:26: ... Location of declaration being extended
+   30 |    function :initial int get_i_i; return 1; endfunction
+      |                          ^~~~~~~
+%Error: t/t_class_override_bad.v:74:33: Member 'get_i_if' is marked ':initial' but is being extended (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   74 |    function :initial :final int get_i_if; return 1; endfunction   
+      |                                 ^~~~~~~~
+        t/t_class_override_bad.v:31:26: ... Location of declaration being extended
+   31 |    function :initial int get_i_if; return 1; endfunction
+      |                          ^~~~~~~~
+%Error: t/t_class_override_bad.v:77:17: Member 'get_if_n' is being extended from member marked ':final' (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   77 |    function int get_if_n; return 1; endfunction   
+      |                 ^~~~~~~~
+        t/t_class_override_bad.v:35:33: ... Location of ':final' declaration being extended
+   35 |    function :initial :final int get_if_n; return 1; endfunction
+      |                                 ^~~~~~~~
+%Error: t/t_class_override_bad.v:78:26: Member 'get_if_e' is being extended from member marked ':final' (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   78 |    function :extends int get_if_e; return 1; endfunction   
+      |                          ^~~~~~~~
+        t/t_class_override_bad.v:36:33: ... Location of ':final' declaration being extended
+   36 |    function :initial :final int get_if_e; return 1; endfunction
+      |                                 ^~~~~~~~
+%Error: t/t_class_override_bad.v:79:33: Member 'get_if_ef' is being extended from member marked ':final' (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   79 |    function :extends :final int get_if_ef; return 1; endfunction   
+      |                                 ^~~~~~~~~
+        t/t_class_override_bad.v:37:33: ... Location of ':final' declaration being extended
+   37 |    function :initial :final int get_if_ef; return 1; endfunction
+      |                                 ^~~~~~~~~
+%Error: t/t_class_override_bad.v:80:26: Member 'get_if_i' is marked ':initial' but is being extended (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   80 |    function :initial int get_if_i; return 1; endfunction   
+      |                          ^~~~~~~~
+        t/t_class_override_bad.v:38:33: ... Location of declaration being extended
+   38 |    function :initial :final int get_if_i; return 1; endfunction
+      |                                 ^~~~~~~~
+%Error: t/t_class_override_bad.v:80:26: Member 'get_if_i' is being extended from member marked ':final' (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   80 |    function :initial int get_if_i; return 1; endfunction   
+      |                          ^~~~~~~~
+        t/t_class_override_bad.v:38:33: ... Location of ':final' declaration being extended
+   38 |    function :initial :final int get_if_i; return 1; endfunction
+      |                                 ^~~~~~~~
+%Error: t/t_class_override_bad.v:81:33: Member 'get_if_if' is marked ':initial' but is being extended (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   81 |    function :initial :final int get_if_if; return 1; endfunction   
+      |                                 ^~~~~~~~~
+        t/t_class_override_bad.v:39:33: ... Location of declaration being extended
+   39 |    function :initial :final int get_if_if; return 1; endfunction
+      |                                 ^~~~~~~~~
+%Error: t/t_class_override_bad.v:81:33: Member 'get_if_if' is being extended from member marked ':final' (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   81 |    function :initial :final int get_if_if; return 1; endfunction   
+      |                                 ^~~~~~~~~
+        t/t_class_override_bad.v:39:33: ... Location of ':final' declaration being extended
+   39 |    function :initial :final int get_if_if; return 1; endfunction
+      |                                 ^~~~~~~~~
+%Error: t/t_class_override_bad.v:82:24: Member 'get_if_f' is being extended from member marked ':final' (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   82 |    function :final int get_if_f; return 1; endfunction   
+      |                        ^~~~~~~~
+        t/t_class_override_bad.v:40:33: ... Location of ':final' declaration being extended
+   40 |    function :initial :final int get_if_f; return 1; endfunction
+      |                                 ^~~~~~~~
+%Error: t/t_class_override_bad.v:84:17: Member 'get_f_n' is being extended from member marked ':final' (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   84 |    function int get_f_n; return 1; endfunction   
+      |                 ^~~~~~~
+        t/t_class_override_bad.v:43:24: ... Location of ':final' declaration being extended
+   43 |    function :final int get_f_n; return 1; endfunction
+      |                        ^~~~~~~
+%Error: t/t_class_override_bad.v:85:26: Member 'get_f_e' is being extended from member marked ':final' (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   85 |    function :extends int get_f_e; return 1; endfunction   
+      |                          ^~~~~~~
+        t/t_class_override_bad.v:44:24: ... Location of ':final' declaration being extended
+   44 |    function :final int get_f_e; return 1; endfunction
+      |                        ^~~~~~~
+%Error: t/t_class_override_bad.v:86:33: Member 'get_f_ef' is being extended from member marked ':final' (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   86 |    function :extends :final int get_f_ef; return 1; endfunction   
+      |                                 ^~~~~~~~
+        t/t_class_override_bad.v:45:24: ... Location of ':final' declaration being extended
+   45 |    function :final int get_f_ef; return 1; endfunction
+      |                        ^~~~~~~~
+%Error: t/t_class_override_bad.v:87:26: Member 'get_f_i' is marked ':initial' but is being extended (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   87 |    function :initial int get_f_i; return 1; endfunction   
+      |                          ^~~~~~~
+        t/t_class_override_bad.v:46:24: ... Location of declaration being extended
+   46 |    function :final int get_f_i; return 1; endfunction
+      |                        ^~~~~~~
+%Error: t/t_class_override_bad.v:87:26: Member 'get_f_i' is being extended from member marked ':final' (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   87 |    function :initial int get_f_i; return 1; endfunction   
+      |                          ^~~~~~~
+        t/t_class_override_bad.v:46:24: ... Location of ':final' declaration being extended
+   46 |    function :final int get_f_i; return 1; endfunction
+      |                        ^~~~~~~
+%Error: t/t_class_override_bad.v:88:33: Member 'get_f_if' is marked ':initial' but is being extended (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   88 |    function :initial :final int get_f_if; return 1; endfunction   
+      |                                 ^~~~~~~~
+        t/t_class_override_bad.v:47:24: ... Location of declaration being extended
+   47 |    function :final int get_f_if; return 1; endfunction
+      |                        ^~~~~~~~
+%Error: t/t_class_override_bad.v:88:33: Member 'get_f_if' is being extended from member marked ':final' (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   88 |    function :initial :final int get_f_if; return 1; endfunction   
+      |                                 ^~~~~~~~
+        t/t_class_override_bad.v:47:24: ... Location of ':final' declaration being extended
+   47 |    function :final int get_f_if; return 1; endfunction
+      |                        ^~~~~~~~
+%Error: t/t_class_override_bad.v:89:24: Member 'get_f_f' is being extended from member marked ':final' (IEEE 1800-2023 8.20)
+                                      : ... note: In instance 't'
+   89 |    function :final int get_f_f; return 1; endfunction   
+      |                        ^~~~~~~
+        t/t_class_override_bad.v:48:24: ... Location of ':final' declaration being extended
+   48 |    function :final int get_f_f; return 1; endfunction
+      |                        ^~~~~~~
+%Error: t/t_class_override_bad.v:101:42: Class 'CClsBadExtendsFinal' is being extended from class marked ':final' (IEEE 1800-2023 8.20)
+                                       : ... note: In instance 't'
+  101 | class :final CClsBadExtendsFinal extends CClsF;
+      |                                          ^~~~~
+        t/t_class_override_bad.v:98:1: ... Location of ':final' class being extended
+   98 | class :final CClsF extends CBase;
+      | ^~~~~
+%Error: Exiting due to

test_regress/t/t_class_override_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 2020 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_override_bad.v

@@ -0,0 +1,116 @@
+// 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
+
+// Function names correspond to how the function is declared in the base class,
+// then the extend class, with letters:
+//   Does-not-exist(x), Nothing(n), :initial(i), :extends(e), :final(f)
+
+class Base;
+   // _X = non-existant
+   // _n = None
+   function int get_n; return 1; endfunction
+   function int get_n_n; return 1; endfunction
+   function int get_n_e; return 1; endfunction
+   function int get_n_ef; return 1; endfunction
+   function int get_n_i; return 1; endfunction
+   function int get_n_if; return 1; endfunction
+   function int get_n_f; return 1; endfunction
+   // _e = :extends
+   function :extends int get_e; return 1; endfunction  // Bad
+   // _ef = :extends :final
+   function :extends :final int get_ef; return 1; endfunction  // Bad
+   // _i = :initial
+   function :initial int get_i; return 1; endfunction
+   function :initial int get_i_n; return 1; endfunction
+   function :initial int get_i_e; return 1; endfunction
+   function :initial int get_i_ef; return 1; endfunction
+   function :initial int get_i_i; return 1; endfunction
+   function :initial int get_i_if; return 1; endfunction
+   function :initial int get_i_f; return 1; endfunction
+   // _if = :initial :final
+   function :initial :final int get_if; return 1; endfunction
+   function :initial :final int get_if_n; return 1; endfunction
+   function :initial :final int get_if_e; return 1; endfunction
+   function :initial :final int get_if_ef; return 1; endfunction
+   function :initial :final int get_if_i; return 1; endfunction
+   function :initial :final int get_if_if; return 1; endfunction
+   function :initial :final int get_if_f; return 1; endfunction
+   // _f = :final
+   function :final int get_f; return 1; endfunction
+   function :final int get_f_n; return 1; endfunction
+   function :final int get_f_e; return 1; endfunction
+   function :final int get_f_ef; return 1; endfunction
+   function :final int get_f_i; return 1; endfunction
+   function :final int get_f_if; return 1; endfunction
+   function :final int get_f_f; return 1; endfunction
+
+endclass
+
+class Cls extends Base;
+   // _X = non-existant
+   function int get_x_n; return 1; endfunction
+   function :extends int get_x_e; return 1; endfunction  // Bad
+   function :extends :final int get_x_ef; return 1; endfunction  // Bad
+   function :initial int get_x_i; return 1; endfunction
+   function :initial :final int get_x_if; return 1; endfunction
+   function :final int get_x_f; return 1; endfunction
+   // _n = None
+   function int get_n_n; return 1; endfunction
+   function :extends int get_n_e; return 1; endfunction
+   function :extends :final int get_n_ef; return 1; endfunction
+   function :initial int get_n_i; return 1; endfunction  // Bad
+   function :initial :final int get_n_if; return 1; endfunction  // Bad
+   function :final int get_n_f; return 1; endfunction
+   // _e = :extends
+   // _ef = :extends :final
+   // _i = :initial
+   function int get_i_n; return 1; endfunction
+   function :extends int get_i_e; return 1; endfunction
+   function :extends :final int get_i_ef; return 1; endfunction
+   function :initial int get_i_i; return 1; endfunction  // Bad
+   function :initial :final int get_i_if; return 1; endfunction  // Bad
+   function :final int get_i_f; return 1; endfunction
+   // _if = :initial :final
+   function int get_if_n; return 1; endfunction  // Bad
+   function :extends int get_if_e; return 1; endfunction  // Bad
+   function :extends :final int get_if_ef; return 1; endfunction  // Bad
+   function :initial int get_if_i; return 1; endfunction  // Bad
+   function :initial :final int get_if_if; return 1; endfunction  // Bad
+   function :final int get_if_f; return 1; endfunction  // Bad
+   // _f = :final
+   function int get_f_n; return 1; endfunction  // Bad
+   function :extends int get_f_e; return 1; endfunction  // Bad
+   function :extends :final int get_f_ef; return 1; endfunction  // Bad
+   function :initial int get_f_i; return 1; endfunction  // Bad
+   function :initial :final int get_f_if; return 1; endfunction  // Bad
+   function :final int get_f_f; return 1; endfunction  // Bad
+endclass
+
+class CBase;
+endclass
+
+class CClsN extends CBase;
+endclass
+
+class :final CClsF extends CBase;
+endclass
+
+class :final CClsBadExtendsFinal extends CClsF;
+endclass
+
+module t (/*AUTOARG*/);
+   initial begin
+      Cls c;
+      CClsF cc;
+
+      if (c != null) $stop;
+      c = new;
+      cc = new;
+
+      $write("*-* All Finished *-*\n");
+      $finish;
+   end
+endmodule