regression in my large design

src/V3Undriven.cpp

@@ -480,13 +480,13 @@ class UndrivenVisitor final : public VNVisitorConst {
                     // EOM
                     //&& entryp->getNodep()) {
                     && (entryp->getNodep()
-                        || (V3UndrivenCapture::enableWriteSummary && entryp->getCallNodep()))) {
+                        || (m_enableWriteSummary && entryp->getCallNodep()))) {
 
                     // EOM
                     const AstNode* const otherWritep
                         = entryp->getNodep()
                               ? static_cast<const AstNode*>(entryp->getNodep())
-                              : (V3UndrivenCapture::enableWriteSummary ? entryp->getCallNodep()
+                              : (m_enableWriteSummary ? entryp->getCallNodep()
                                                                        : nullptr);
 
                     if (m_alwaysCombp

src/V3UndrivenCapture.cpp

@@ -69,7 +69,13 @@ private:
             UINFO(DBG, "UndrivenCapture: direct write in "
                            << taskNameQ(m_curTaskp) << " var=" << nodep->varp()->prettyNameQ()
                            << " at " << nodep->fileline());
-            m_cap.info(m_curTaskp).directWrites.push_back(nodep->varp());
+            //m_cap.info(m_curTaskp).directWrites.push_back(nodep->varp());
+            AstVar* const retVarp = VN_CAST(m_curTaskp->fvarp(), Var);
+            if (retVarp && nodep->varp() == retVarp) {
+                // Skip: function return variable is local, not a side-effect
+            } else {
+                m_cap.info(m_curTaskp).directWrites.push_back(nodep->varp());
+            }
         }
         iterateChildrenConst(nodep);
     }

test_regress/t/t_multidriven_funcret0.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"])
+
+test.execute()
+
+test.passes()

test_regress/t/t_multidriven_funcret0.v

@@ -0,0 +1,37 @@
+// DESCRIPTION: Verilator: MULTIDRIVEN false positive - package function return var
+//
+// Minimal reproducer for: package function with "return expr" used in always_comb expression.
+// The function return variable must not be treated as a side-effect "writeSummary" target.
+
+`define stop $stop
+`define checkd(gotv,expv) do if ((gotv) !== (expv)) begin $write("%%Error: %s:%0d:  got=%0d exp=%0d (%s !== %s)\n", `__FILE__,`__LINE__, (gotv), (expv), `"gotv`", `"expv`"); `stop; end while(0);
+
+package p;
+  function automatic int num_bytes(input int size);
+    return 1 << size;
+  endfunction
+endpackage
+
+module t;
+  typedef struct packed {
+    logic [31:0] addr;
+    logic [2:0]  size;
+  } meta_t;
+
+  meta_t rd_meta_q;
+  meta_t rd_meta;
+
+  always_comb begin
+    rd_meta = rd_meta_q;
+    rd_meta.addr = rd_meta_q.addr + p::num_bytes(int'(rd_meta_q.size));
+  end
+
+  initial begin
+    rd_meta_q.addr = 32'h100;
+    rd_meta_q.size = 3'd2;  // num_bytes = 4
+    #1;
+    `checkd(rd_meta.addr, 32'h104);
+    $write("*-* All Finished *-*\n");
+    $finish;
+  end
+endmodule