Add ALWNEVER warning, for `always @*` that never execute (#6291) (#6303)

Changes

@@ -20,6 +20,7 @@ Verilator 5.039 devel
 * Add enum base data type, wire data type, and I/O versus data declaration checking per IEEE.
 * Add PROTOTYPEMIS error on missing and mismatching prototypes (#6206) (#6207). [Alex Solomatnikov]
 * Add error when trying to assign class object to variable of non-class types (#6237). [Igor Zaworski, Antmicro Ltd.]
+* Add ALWNEVER warning, for `always @*` that never execute (#6291).
 * Add error on class 'function static'.
 * Add `-DVERILATOR=1` definition to compiler flags when using verilated.mk.
 * Support member-level triggers for virtual interfaces (#5166) (#6148). [Yilou Wang]

docs/gen/ex_ALWNEVER_faulty.rst

@@ -0,0 +1,4 @@
+.. comment: generated by t_event_control_star_never_bad
+.. code-block:: sv
+
+     always @* a = 100;

docs/gen/ex_ALWNEVER_msg.rst

@@ -0,0 +1,4 @@
+.. comment: generated by t_event_control_star_never_bad
+.. code-block::
+
+   %Warning-ALWNEVER: example.v:1:3 'always @*' will never execute as expression list is empty (no variables read)

docs/guide/warnings.rst

@@ -111,6 +111,27 @@ List Of Warnings
    simulate correctly.
 
 
+.. option:: ALWNEVER
+
+   Warning that an `always @*` statement has no variables being read,
+   therefore the event list is empty, and as there are no events to wake
+   the process up, the always will never execute.
+
+   Faulty example:
+
+   .. include:: ../../docs/gen/ex_ALWNEVER_faulty.rst
+
+   Results in:
+
+   .. include:: ../../docs/gen/ex_ALWNEVER_msg.rst
+
+   To repair, assuming the intent was to execute the statements at e.g.
+   time zero, instead use an `always_comb` statement.
+
+   Ignoring this warning will only suppress the lint check; it will
+   simulate correctly.
+
+
 .. option:: ASCRANGE
 
    .. TODO better example

src/V3Ast.h

@@ -406,6 +406,7 @@ public:
         ET_TRUE,
         //
         ET_COMBO,  // Sensitive to all combo inputs to this block
+        ET_COMBO_STAR,  // Sensitive to all combo inputs to this block (from .*)
         ET_HYBRID,  // This is like ET_COMB, but with explicit sensitivity to an expression
         ET_STATIC,  // static variable initializers (runs before 'initial')
         ET_INITIAL,  // 'initial' statements
@@ -423,6 +424,7 @@ public:
             true,  // ET_TRUE
 
             false,  // ET_COMBO
+            false,  // ET_COMBO_STAR
             false,  // ET_HYBRID
             false,  // ET_STATIC
             false,  // ET_INITIAL
@@ -443,13 +445,13 @@ public:
     }
     const char* ascii() const {
         static const char* const names[]
-            = {"CHANGED", "BOTH",   "POS",    "NEG",     "EVENT", "TRUE",
+            = {"CHANGED",    "BOTH",   "POS",    "NEG",     "EVENT", "TRUE", "COMBO",
-               "COMBO",   "HYBRID", "STATIC", "INITIAL", "FINAL", "NEVER"};
+               "COMBO_STAR", "HYBRID", "STATIC", "INITIAL", "FINAL", "NEVER"};
         return names[m_e];
     }
     const char* verilogKwd() const {
         static const char* const names[]
-            = {"[changed]", "edge",     "posedge",  "negedge",   "[event]", "[true]",
+            = {"[changed]", "edge",     "posedge",  "negedge",   "[event]", "[true]", "*",
                "*",         "[hybrid]", "[static]", "[initial]", "[final]", "[never]"};
         return names[m_e];
     }

src/V3AstNodeOther.h

@@ -1533,7 +1533,10 @@ public:
     AstNodeVarRef* varrefp() const { return VN_CAST(sensp(), NodeVarRef); }
     //
     bool isClocked() const { return edgeType().clockedStmt(); }
-    bool isCombo() const { return edgeType() == VEdgeType::ET_COMBO; }
+    bool isComboOrStar() const {
+        return edgeType() == VEdgeType::ET_COMBO || edgeType() == VEdgeType::ET_COMBO_STAR;
+    }
+    bool isComboStar() const { return edgeType() == VEdgeType::ET_COMBO_STAR; }
     bool isHybrid() const { return edgeType() == VEdgeType::ET_HYBRID; }
     bool isStatic() const { return edgeType() == VEdgeType::ET_STATIC; }
     bool isInitial() const { return edgeType() == VEdgeType::ET_INITIAL; }
@@ -1550,6 +1553,10 @@ public:
         addSensesp(sensesp);
     }
     ASTGEN_MEMBERS_AstSenTree;
+    bool sameNode(const AstNode* samep) const override {
+        const AstSenTree* const asamep = VN_DBG_AS(samep, SenTree);
+        return m_multi == asamep->m_multi;
+    }
     void dump(std::ostream& str) const override;
     void dumpJson(std::ostream& str) const override;
     bool maybePointedTo() const override VL_MT_SAFE { return true; }

src/V3AstNodes.cpp

@@ -1254,7 +1254,7 @@ bool AstSenTree::hasFinal() const {
 bool AstSenTree::hasCombo() const {
     UASSERT_OBJ(sensesp(), this, "SENTREE without any SENITEMs under it");
     for (AstSenItem* senp = sensesp(); senp; senp = VN_AS(senp->nextp(), SenItem)) {
-        if (senp->isCombo()) return true;
+        if (senp->isComboOrStar()) return true;
     }
     return false;
 }

src/V3Clock.cpp

@@ -80,8 +80,10 @@ class ClockVisitor final : public VNVisitor {
         AstNodeExpr* senEqnp = nullptr;
         for (AstSenItem* senp = nodesp; senp; senp = VN_AS(senp->nextp(), SenItem)) {
             UASSERT_OBJ(senp->edgeType() == VEdgeType::ET_TRUE, senp, "Should have been lowered");
-            AstNodeExpr* const senOnep = senp->sensp()->cloneTree(false);
+            if (senp->sensp()) {
-            senEqnp = senEqnp ? new AstOr{senp->fileline(), senEqnp, senOnep} : senOnep;
+                AstNodeExpr* const senOnep = senp->sensp()->cloneTree(false);
+                senEqnp = senEqnp ? new AstOr{senp->fileline(), senEqnp, senOnep} : senOnep;
+            }
         }
         return senEqnp;
     }

src/V3Delayed.cpp

@@ -1119,7 +1119,8 @@ class DelayedVisitor final : public VNVisitor {
         // First gather all senItems
         AstSenItem* senItemp = nullptr;
         for (AstSenTree* const domainp : m_timingDomains) {
-            senItemp = AstNode::addNext(senItemp, domainp->sensesp()->cloneTree(true));
+            if (domainp->sensesp())
+                senItemp = AstNode::addNext(senItemp, domainp->sensesp()->cloneTree(true));
         }
         m_timingDomains.clear();
         // Add them to all nba targets we gathered in this process

src/V3Error.h

@@ -71,6 +71,7 @@ public:
         EC_FIRST_WARN,  // Just a code so the program knows where to start warnings
         //
         ALWCOMBORDER,   // Always_comb with unordered statements
+        ALWNEVER,       // always will never execute
         ASCRANGE,       // Ascending bit range vector
         ASSIGNDLY,      // Assignment delays
         ASSIGNIN,       // Assigning to input
@@ -203,18 +204,18 @@ public:
             // Errors
             "LIFETIME", "NEEDTIMINGOPT", "NOTIMING", "PORTSHORT", "TASKNSVAR", "UNSUPPORTED",
             // Warnings
-            " EC_FIRST_WARN", "ALWCOMBORDER", "ASCRANGE", "ASSIGNDLY", "ASSIGNIN", "BADSTDPRAGMA",
+            " EC_FIRST_WARN", "ALWCOMBORDER", "ALWNEVER", "ASCRANGE", "ASSIGNDLY", "ASSIGNIN",
-            "BADVLTPRAGMA", "BLKANDNBLK", "BLKLOOPINIT", "BLKSEQ", "BSSPACE", "CASEINCOMPLETE",
+            "BADSTDPRAGMA", "BADVLTPRAGMA", "BLKANDNBLK", "BLKLOOPINIT", "BLKSEQ", "BSSPACE",
-            "CASEOVERLAP", "CASEWITHX", "CASEX", "CASTCONST", "CDCRSTLOGIC", "CLKDATA", "CMPCONST",
+            "CASEINCOMPLETE", "CASEOVERLAP", "CASEWITHX", "CASEX", "CASTCONST", "CDCRSTLOGIC",
-            "COLONPLUS", "COMBDLY", "CONSTRAINTIGN", "CONTASSREG", "COVERIGN", "DECLFILENAME",
+            "CLKDATA", "CMPCONST", "COLONPLUS", "COMBDLY", "CONSTRAINTIGN", "CONTASSREG",
-            "DEFOVERRIDE", "DEFPARAM", "DEPRECATED", "ENCAPSULATED", "ENDLABEL", "ENUMITEMWIDTH",
+            "COVERIGN", "DECLFILENAME", "DEFOVERRIDE", "DEFPARAM", "DEPRECATED", "ENCAPSULATED",
-            "ENUMVALUE", "EOFNEWLINE", "GENCLK", "GENUNNAMED", "HIERBLOCK", "IFDEPTH",
+            "ENDLABEL", "ENUMITEMWIDTH", "ENUMVALUE", "EOFNEWLINE", "GENCLK", "GENUNNAMED",
-            "IGNOREDRETURN", "IMPERFECTSCH", "IMPLICIT", "IMPLICITSTATIC", "IMPORTSTAR", "IMPURE",
+            "HIERBLOCK", "IFDEPTH", "IGNOREDRETURN", "IMPERFECTSCH", "IMPLICIT", "IMPLICITSTATIC",
-            "INCABSPATH", "INFINITELOOP", "INITIALDLY", "INSECURE", "LATCH", "LITENDIAN",
+            "IMPORTSTAR", "IMPURE", "INCABSPATH", "INFINITELOOP", "INITIALDLY", "INSECURE",
-            "MINTYPMAXDLY", "MISINDENT", "MODDUP", "MODMISSING", "MULTIDRIVEN", "MULTITOP",
+            "LATCH", "LITENDIAN", "MINTYPMAXDLY", "MISINDENT", "MODDUP", "MODMISSING",
-            "NEWERSTD", "NOEFFECT", "NOLATCH", "NONSTD", "NULLPORT", "PARAMNODEFAULT",
+            "MULTIDRIVEN", "MULTITOP", "NEWERSTD", "NOEFFECT", "NOLATCH", "NONSTD", "NULLPORT",
-            "PINCONNECTEMPTY", "PINMISSING", "PINNOCONNECT", "PINNOTFOUND", "PKGNODECL",
+            "PARAMNODEFAULT", "PINCONNECTEMPTY", "PINMISSING", "PINNOCONNECT", "PINNOTFOUND",
-            "PREPROCZERO", "PROCASSINIT", "PROCASSWIRE", "PROFOUTOFDATE", "PROTECTED",
+            "PKGNODECL", "PREPROCZERO", "PROCASSINIT", "PROCASSWIRE", "PROFOUTOFDATE", "PROTECTED",
             "PROTOTYPEMIS", "RANDC", "REALCVT", "REDEFMACRO", "RISEFALLDLY", "SELRANGE",
             "SHORTREAL", "SIDEEFFECT", "SPECIFYIGN", "SPLITVAR", "STATICVAR", "STMTDLY",
             "SYMRSVDWORD", "SYNCASYNCNET", "TICKCOUNT", "TIMESCALEMOD", "UNDRIVEN", "UNOPT",

src/V3LinkParse.cpp

@@ -835,7 +835,7 @@ class LinkParseVisitor final : public VNVisitor {
         if (alwaysp && alwaysp->keyword() == VAlwaysKwd::ALWAYS_COMB) {
             alwaysp->v3error("Event control statements not legal under always_comb "
                              "(IEEE 1800-2023 9.2.2.2.2)\n"
-                             << nodep->warnMore() << "... Suggest use a normal 'always'");
+                             << alwaysp->warnMore() << "... Suggest use a normal 'always'");
             VL_DO_DANGLING(nodep->unlinkFrBack()->deleteTree(), nodep);
         } else if (alwaysp && !alwaysp->sentreep()) {
             // If the event control is at the top, move the sentree to the always

src/V3SchedPartition.cpp

@@ -162,9 +162,11 @@ class SchedGraphBuilder final : public VNVisitor {
                 SchedSenVertex* const vtxp = new SchedSenVertex{m_graphp, senItemp};
 
                 // Connect up the variable references
-                senItemp->sensp()->foreach([&](AstVarRef* refp) {
+                if (senItemp->sensp()) {
-                    new V3GraphEdge{m_graphp, getVarVertex(refp->varScopep()), vtxp, 1};
+                    senItemp->sensp()->foreach([&](AstVarRef* refp) {
-                });
+                        new V3GraphEdge{m_graphp, getVarVertex(refp->varScopep()), vtxp, 1};
+                    });
+                }
 
                 // Store back to hash map so we can find it next time
                 pair.first->second = vtxp;

src/V3Timing.cpp

@@ -905,8 +905,11 @@ class TimingControlVisitor final : public VNVisitor {
     void visit(AstEventControl* nodep) override {
         // Do not allow waiting on local named events, as they get enqueued for clearing, but can
         // go out of scope before that happens
-        if (!nodep->sentreep())
+        if (!nodep->sentreep()) {
             nodep->v3warn(E_UNSUPPORTED, "Unsupported: no sense equation (@*)");
+            VL_DO_DANGLING(pushDeletep(nodep->unlinkFrBack()), nodep);
+            return;
+        }
         FileLine* const flp = nodep->fileline();
         // Relink child statements after the event control
         if (nodep->stmtsp()) nodep->addNextHere(nodep->stmtsp()->unlinkFrBackWithNext());

src/V3Width.cpp

@@ -6556,6 +6556,7 @@ class WidthVisitor final : public VNVisitor {
         userIterateChildren(nodep, nullptr);
     }
     void visit(AstSenItem* nodep) override {
+        if (nodep->isComboStar()) return;
         UASSERT_OBJ(nodep->isClocked(), nodep, "Invalid edge");
         // Optimize concat/replicate senitems; this has to be done here at the latest, otherwise we
         // emit WIDTHCONCAT if there are unsized constants

src/V3WidthCommit.cpp

@@ -168,6 +168,36 @@ private:
             }
         }
     }
+    void visit(AstAlways* nodep) override {
+        // As have not optimized SenTrees yet, an 'always .*' will be on first and only SenItem
+        if (nodep->sentreep() && nodep->sentreep()->sensesp()
+            && nodep->sentreep()->sensesp()->isComboStar()) {
+            const bool noReads = nodep->forall(
+                [&](const AstNodeVarRef* refp) { return !refp->access().isReadOrRW(); });
+            if (noReads) {
+                nodep->v3warn(ALWNEVER, "'always @*' will never execute as expression list is "
+                                        "empty (no variables read)\n"
+                                            << nodep->warnMore()
+                                            << "... Suggest use 'always_comb'");
+                VL_DO_DANGLING(pushDeletep(nodep->unlinkFrBack()), nodep);
+                return;
+            }
+        }
+        // Iterate will delete ComboStar sentrees, so after above
+        iterateChildren(nodep);
+        editDType(nodep);
+    }
+    void visit(AstSenTree* nodep) override {
+        if (nodep->sensesp() && nodep->sensesp()->isComboStar()) {
+            UASSERT_OBJ(!nodep->sensesp()->nextp(), nodep, "Shouldn't be senitems after .*");
+            // Make look like standalone always
+            // (Rest of code assumed this before .* existed)
+            VL_DO_DANGLING(pushDeletep(nodep->unlinkFrBack()), nodep);
+            return;
+        }
+        iterateChildren(nodep);
+        editDType(nodep);
+    }
     void visit(AstAttrOf* nodep) override {
         switch (nodep->attrType()) {
         case VAttrType::FUNC_ARG_PROTO:  // FALLTHRU

src/verilog.y

@@ -160,14 +160,17 @@ public:
             return new AstGatePin{rangep->fileline(), exprp, rangep->cloneTree(true)};
         }
     }
-    AstSenTree* createClockSenTree(FileLine* fl, AstNodeExpr* exprp) {
+    AstSenTree* createSenTreeChanged(FileLine* fl, AstNodeExpr* exprp) {
         return new AstSenTree{fl, new AstSenItem{fl, VEdgeType::ET_CHANGED, exprp}};
     }
+    AstSenTree* createSenTreeDotStar(FileLine* fl) {
+        return new AstSenTree{fl, new AstSenItem{fl, VEdgeType::ET_COMBO_STAR, nullptr}};
+    }
     AstNodeExpr* createGlobalClockParseRef(FileLine* fl) {
         return new AstParseRef{fl, VParseRefExp::PX_TEXT, "__024global_clock", nullptr, nullptr};
     }
     AstSenTree* createGlobalClockSenTree(FileLine* fl) {
-        return createClockSenTree(fl, createGlobalClockParseRef(fl));
+        return createSenTreeChanged(fl, createGlobalClockParseRef(fl));
     }
     AstNode* createNettype(FileLine* fl, const string& name) {
         // As nettypes are unsupported, we just alias to logic
@@ -2817,7 +2820,6 @@ module_common_item<nodep>:      // ==IEEE: module_common_item
         ;
 
 always_construct<nodep>:        // IEEE: == always_construct
-        //                      // Verilator only - event_control attached to always
                 yALWAYS       stmtBlock                 { $$ = new AstAlways{$1, VAlwaysKwd::ALWAYS, nullptr, $2}; }
         |       yALWAYS_FF    stmtBlock                 { $$ = new AstAlways{$1, VAlwaysKwd::ALWAYS_FF, nullptr, $2}; }
         |       yALWAYS_LATCH stmtBlock                 { $$ = new AstAlways{$1, VAlwaysKwd::ALWAYS_LATCH, nullptr, $2}; }
@@ -3492,14 +3494,14 @@ attr_event_controlE<senTreep>:
 
 attr_event_control<senTreep>:   // ==IEEE: event_control
                 '@' '(' event_expression ')'            { $$ = new AstSenTree{$1, $3}; }
-        |       '@' '(' '*' ')'                         { $$ = nullptr; }
+        |       '@' '(' '*' ')'                         { $$ = GRAMMARP->createSenTreeDotStar($1); }
-        |       '@' '*'                                 { $$ = nullptr; }
+        |       '@' '*'                                 { $$ = GRAMMARP->createSenTreeDotStar($1); }
         ;
 
 event_control<senTreep>:        // ==IEEE: event_control
         // UNSUP: Needs alignment with IEEE event_control and clocking_event
-                '@' '(' '*' ')'                         { $$ = nullptr; }
+                '@' '(' '*' ')'                         { $$ = GRAMMARP->createSenTreeDotStar($1); }
-        |       '@' '*'                                 { $$ = nullptr; }
+        |       '@' '*'                                 { $$ = GRAMMARP->createSenTreeDotStar($1); }
         //                      // IEEE: clocking_event
         |       '@' '(' event_expression ')'            { $$ = new AstSenTree{$1, $3}; }
         //                      // IEEE: hierarchical_event_identifier
@@ -4464,7 +4466,7 @@ system_f_call_or_t<nodeExprp>:      // IEEE: part of system_tf_call (can be task
         |       yD_CEIL '(' expr ')'                    { $$ = new AstCeilD{$1, $3}; }
         |       yD_CHANGED '(' expr ')'                 { $$ = new AstLogNot{$1, new AstStable{$1, $3, nullptr}}; }
         |       yD_CHANGED '(' expr ',' expr ')'
-                        { $$ = new AstLogNot{$1, new AstStable{$1, $3, GRAMMARP->createClockSenTree($1, $5)}}; }
+                        { $$ = new AstLogNot{$1, new AstStable{$1, $3, GRAMMARP->createSenTreeChanged($1, $5)}}; }
         |       yD_CHANGED_GCLK '(' expr ')'
                         { $$ = new AstLogNot{$1, new AstStable{$1, $3, GRAMMARP->createGlobalClockSenTree($1)}}; }
         |       yD_CLOG2 '(' expr ')'                   { $$ = new AstCLog2{$1, $3}; }
@@ -4487,7 +4489,7 @@ system_f_call_or_t<nodeExprp>:      // IEEE: part of system_tf_call (can be task
         |       yD_DIST_UNIFORM '(' expr ',' expr ',' expr ')'  { $$ = new AstDistUniform{$1, $3, $5, $7}; }
         |       yD_EXP '(' expr ')'                     { $$ = new AstExpD{$1, $3}; }
         |       yD_FELL '(' expr ')'                    { $$ = new AstFell{$1, $3, nullptr}; }
-        |       yD_FELL '(' expr ',' expr ')'           { $$ = new AstFell{$1, $3, GRAMMARP->createClockSenTree($1, $5)}; }
+        |       yD_FELL '(' expr ',' expr ')'           { $$ = new AstFell{$1, $3, GRAMMARP->createSenTreeChanged($1, $5)}; }
         |       yD_FELL_GCLK '(' expr ')'               { $$ = new AstFell{$1, $3, GRAMMARP->createGlobalClockSenTree($1)}; }
         |       yD_FEOF '(' expr ')'                    { $$ = new AstFEof{$1, $3}; }
         |       yD_FERROR '(' expr ',' idClassSel ')'   { $$ = new AstFError{$1, $3, $5}; }
@@ -4539,7 +4541,7 @@ system_f_call_or_t<nodeExprp>:      // IEEE: part of system_tf_call (can be task
         |       yD_RIGHT '(' exprOrDataType ')'         { $$ = new AstAttrOf{$1, VAttrType::DIM_RIGHT, $3, nullptr}; }
         |       yD_RIGHT '(' exprOrDataType ',' expr ')'        { $$ = new AstAttrOf{$1, VAttrType::DIM_RIGHT, $3, $5}; }
         |       yD_ROSE '(' expr ')'                    { $$ = new AstRose{$1, $3, nullptr}; }
-        |       yD_ROSE '(' expr ',' expr ')'           { $$ = new AstRose{$1, $3, GRAMMARP->createClockSenTree($1, $5)}; }
+        |       yD_ROSE '(' expr ',' expr ')'           { $$ = new AstRose{$1, $3, GRAMMARP->createSenTreeChanged($1, $5)}; }
         |       yD_ROSE_GCLK '(' expr ')'               { $$ = new AstRose{$1, $3, GRAMMARP->createGlobalClockSenTree($1)}; }
         |       yD_RTOI '(' expr ')'                    { $$ = new AstRToIS{$1, $3}; }
         |       yD_SAMPLED '(' expr ')'                 { $$ = new AstSampled{$1, $3}; }
@@ -4555,7 +4557,7 @@ system_f_call_or_t<nodeExprp>:      // IEEE: part of system_tf_call (can be task
         |       yD_STIME parenE
                         { $$ = new AstSel{$1, new AstTime{$1, VTimescale{VTimescale::NONE}}, 0, 32}; }
         |       yD_STABLE '(' expr ')'                  { $$ = new AstStable{$1, $3, nullptr}; }
-        |       yD_STABLE '(' expr ',' expr ')'         { $$ = new AstStable{$1, $3, GRAMMARP->createClockSenTree($1, $5)}; }
+        |       yD_STABLE '(' expr ',' expr ')'         { $$ = new AstStable{$1, $3, GRAMMARP->createSenTreeChanged($1, $5)}; }
         |       yD_STABLE_GCLK '(' expr ')'             { $$ = new AstStable{$1, $3, GRAMMARP->createGlobalClockSenTree($1)}; }
         |       yD_TAN '(' expr ')'                     { $$ = new AstTanD{$1, $3}; }
         |       yD_TANH '(' expr ')'                    { $$ = new AstTanhD{$1, $3}; }

test_regress/t/t_event_control_star.out

@@ -1,6 +1,5 @@
-%Error-UNSUPPORTED: t/t_event_control_star.v:19:14: Unsupported: no sense equation (@*)
+%Error-UNSUPPORTED: t/t_event_control_star.v:19:6: Unsupported: no sense equation (@*)
    19 |      @* a = c;   
-      |              ^
+      |      ^
                     ... For error description see https://verilator.org/warn/UNSUPPORTED?v=latest
-%Error: Verilator internal fault, sorry. Suggest trying --debug --gdbbt
+%Error: Exiting due to
-%Error: Command Failed

test_regress/t/t_event_control_star_never.py

@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2025 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
+
+import vltest_bootstrap
+
+test.scenarios('simulator')
+
+test.compile(verilator_flags2=['--binary', '-Wno-ALWNEVER'])
+
+test.execute()
+
+test.passes()

test_regress/t/t_event_control_star_never.v

@@ -0,0 +1,14 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2025 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+module t;
+  int a;
+  always @* a = 100;
+  initial begin
+    #1;
+    if (a != 0) $stop;
+  end
+endmodule

test_regress/t/t_event_control_star_never_bad.out

@@ -0,0 +1,8 @@
+%Warning-ALWNEVER: t/t_event_control_star_never.v:9:3: 'always @*' will never execute as expression list is empty (no variables read)
+                                                     : ... note: In instance 't'
+                                                     : ... Suggest use 'always_comb'
+    9 |   always @* a = 100;
+      |   ^~~~~~
+                   ... For warning description see https://verilator.org/warn/ALWNEVER?v=latest
+                   ... Use "/* verilator lint_off ALWNEVER */" and lint_on around source to disable this message.
+%Error: Exiting due to

test_regress/t/t_event_control_star_never_bad.py

@@ -0,0 +1,30 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2025 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
+
+import vltest_bootstrap
+
+test.scenarios('linter')
+test.top_filename = 't/t_event_control_star_never.v'
+
+root = ".."
+
+if not os.path.exists(root + "/.git"):
+    test.skip("Not in a git repository")
+
+test.lint(verilator_flags2=['--timing'], fails=True, expect_filename=test.golden_filename)
+
+test.extract(in_filename=test.top_filename,
+             out_filename=root + "/docs/gen/ex_ALWNEVER_faulty.rst",
+             lines="9-9")
+
+test.extract(in_filename=test.golden_filename,
+             out_filename=root + "/docs/gen/ex_ALWNEVER_msg.rst",
+             lines="1-1")
+
+test.passes()

test_regress/t/t_lint_blksync_bad.v

@@ -26,7 +26,7 @@ module t (/*AUTOARG*/
       sync_nblk <= 1'b1;
    end
 
-   always @* begin
+   always_comb begin
       combo_blk = 1'b1;
       combo_nblk <= 1'b1;
    end

test_regress/t/t_math_vgen.v

@@ -214,7 +214,7 @@ module t (/*AUTOARG*/
 
    reg signed [ 82:0] W0226                     ; //=47A4301EE3FB4133EE3DA
 
-   always @* begin : Block144
+   always_comb begin : Block144
       W0226 = 83'sh47A4301EE3FB4133EE3DA;
       if ((W0226 >>> 8'sh1a) != 83'sh7ffffff1e90c07b8fed04) if (check) $stop;
    end