From 07b61d3745e27247a32964995cda29b49edbe02a Mon Sep 17 00:00:00 2001
From: Wilson Snyder <wsnyder@wsnyder.org>
Date: Fri, 23 Jan 2026 22:11:04 -0500
Subject: [PATCH] Fix internal error when fork under always expression (#6911).

---
 Changes                               |  1 +
 src/V3Timing.cpp                      | 10 +++++++++-
 test_regress/t/t_class_trigger_null.v |  6 +++---
 3 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/Changes b/Changes
index bf03ff5e9..0d1cf5bb9 100644
--- a/Changes
+++ b/Changes
@@ -41,6 +41,7 @@ Verilator 5.045 devel
 * Fix signedness of packed array (#6901) (#6902). [Yutetsu TAKATSUKASA]
 * Fix assignment of queue from unpacked array (#6906).
 * Fix `foreach` with mid-index empty commas (#6910).
+* Fix internal error when fork under always expression (#6911).
 * Fix error when calling non-static method (#6916). [Artur Bieniek, Antmicro Ltd.]
 * Fix memory leak in vpi_put_value and vpi_get_value (#6917). [Christian Hecken]
 * Fix segfault after assignment pattern XOR error (#6928) (#6931). [emmettifelts]
diff --git a/src/V3Timing.cpp b/src/V3Timing.cpp
index 23cc9ff7e..770c2127a 100644
--- a/src/V3Timing.cpp
+++ b/src/V3Timing.cpp
@@ -277,6 +277,7 @@ class TimingSuspendableVisitor final : public VNVisitor {
         addFlags(m_procp, T_FORCES_PROC | T_NEEDS_PROC);
     }
     void visit(AstWait* nodep) override {
+        UINFO(9, "suspendable-visit " << nodep);
         AstNodeExpr* const condp = V3Const::constifyEdit(nodep->condp());
         if (AstConst* const constp = VN_CAST(condp, Const)) {
             if (!nodep->fileline()->warnIsOff(V3ErrorCode::WAITCONST)) {
@@ -365,6 +366,7 @@ class TimingSuspendableVisitor final : public VNVisitor {
         iterateChildren(nodep);
     }
     void visit(AstFork* nodep) override {
+        UINFO(9, "suspendable-visit " << nodep);
         VL_RESTORER(m_underFork);
 
         v3Global.setUsesTiming();  // Even if there are no event controls, we have to set this flag
@@ -1056,6 +1058,7 @@ class TimingControlVisitor final : public VNVisitor {
     void visit(AstNodeAssign* nodep) override {
         // Only process once to avoid infinite loops (due to the net delay)
         if (nodep->user1SetOnce()) return;
+        UINFO(9, "control-visit " << nodep);
         FileLine* const flp = nodep->fileline();
         AstNode* controlp = factorOutTimingControl(nodep);
         const bool inAssignDly = VN_IS(nodep, AssignDly);
@@ -1063,7 +1066,10 @@ class TimingControlVisitor final : public VNVisitor {
         // Transform if:
         // * there's a timing control in the assignment
         // * the assignment is an AssignDly and it's in a non-inlined function
-        if (!controlp && (!inAssignDly || m_underProcedure)) return;
+        if (!controlp && (!inAssignDly || m_underProcedure)) {
+            iterateChildren(nodep);
+            return;
+        }
         // Insert new vars before the timing control if we're in a function; in a process we can't
         // do that. These intra-assignment vars will later be passed to forked processes by value.
         AstNode* insertBeforep = m_underProcedure ? nullptr : controlp;
@@ -1232,6 +1238,7 @@ class TimingControlVisitor final : public VNVisitor {
     }
     void visit(AstWait* nodep) override {
         // Wait on changed events related to the vars in the wait statement
+        UINFO(9, "control-visit " << nodep);
         FileLine* const flp = nodep->fileline();
         AstNode* const stmtsp = nodep->stmtsp();
         if (stmtsp) stmtsp->unlinkFrBackWithNext();
@@ -1290,6 +1297,7 @@ class TimingControlVisitor final : public VNVisitor {
     }
     void visit(AstFork* nodep) override {
         if (nodep->user1SetOnce()) return;
+        UINFO(9, "control-visit " << nodep);
         v3Global.setUsesTiming();
 
         // Create a unique name for this fork
diff --git a/test_regress/t/t_class_trigger_null.v b/test_regress/t/t_class_trigger_null.v
index 4288a8761..d16f3952f 100644
--- a/test_regress/t/t_class_trigger_null.v
+++ b/test_regress/t/t_class_trigger_null.v
@@ -55,7 +55,7 @@ package my_pkg;
       end
       begin
         #10;
-        -> h.my_event;
+        ->h.my_event;
         #10;
         h.vif.sig = 1;
         #10;
@@ -67,7 +67,7 @@ package my_pkg;
 endpackage
 
 module t;
-  my_if intf();
+  my_if intf ();
   my_pkg::my_driver drv;
   virtual my_if vif;
 
@@ -96,7 +96,7 @@ module t;
   // Use #0 to ensure construction happens first in delta cycle ordering
   initial begin
     #0;
-    -> drv.my_event;
+    ->drv.my_event;
   end
 
   // Call the task later - trigger expressions were evaluated before this