From 3fc70b61d08b744b48e38ca7879024436fc8efd4 Mon Sep 17 00:00:00 2001
From: Matthew Ballance <matt.ballance@gmail.com>
Date: Tue, 2 Dec 2025 19:05:59 -0800
Subject: [PATCH] Fix internal fault when cross-class calling with DPI (#6735)
 (#6742)

Signed-off-by: Matthew Ballance <matt.ballance@gmail.com>
---
 src/V3Task.cpp                      | 16 ++++++---
 test_regress/t/t_dpi_inline_new.cpp | 26 +++++++++++++++
 test_regress/t/t_dpi_inline_new.py  | 19 +++++++++++
 test_regress/t/t_dpi_inline_new.v   | 51 +++++++++++++++++++++++++++++
 4 files changed, 108 insertions(+), 4 deletions(-)
 create mode 100644 test_regress/t/t_dpi_inline_new.cpp
 create mode 100755 test_regress/t/t_dpi_inline_new.py
 create mode 100644 test_regress/t/t_dpi_inline_new.v

diff --git a/src/V3Task.cpp b/src/V3Task.cpp
index bd82d3624..0c53467f4 100644
--- a/src/V3Task.cpp
+++ b/src/V3Task.cpp
@@ -1520,14 +1520,22 @@ class TaskVisitor final : public VNVisitor {
 
             if (m_inNew) {
                 AstVar* varp = outvscp->varp();
-                varp->funcLocal(true);
 
                 // Create a new var that will be inside the lambda
                 AstVar* newvarp = varp->cloneTree(false);
+                newvarp->funcLocal(true);
 
-                // Replace all references so they point to the new var
-                lambdap->stmtsp()->foreachAndNext([varp, newvarp](AstVarRef* refp) {
-                    if (refp->varp() == varp) refp->varp(newvarp);
+                // Create a new VarScope for the new variable
+                AstVarScope* const newvscp
+                    = new AstVarScope{newvarp->fileline(), m_scopep, newvarp};
+                m_scopep->addVarsp(newvscp);
+
+                // Replace all references so they point to the new var and varscope
+                lambdap->stmtsp()->foreachAndNext([outvscp, newvscp](AstVarRef* refp) {
+                    if (refp->varScopep() == outvscp) {
+                        refp->varScopep(newvscp);
+                        refp->varp(newvscp->varp());
+                    }
                 });
 
                 // Add variable initialization
diff --git a/test_regress/t/t_dpi_inline_new.cpp b/test_regress/t/t_dpi_inline_new.cpp
new file mode 100644
index 000000000..bb2877cc1
--- /dev/null
+++ b/test_regress/t/t_dpi_inline_new.cpp
@@ -0,0 +1,26 @@
+// DESCRIPTION: Verilator: DPI stub for t_dpi_inline_new
+//
+// 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
+
+// Include the Verilator-generated DPI header so the C prototype matches
+// the SystemVerilog import expectations.
+#include "Vt_dpi_inline_new__Dpi.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Stub implementation for _pyhdl_if_PyTuple_GetItem used by pyhdl_if package.
+// Returns a null pointer; the SystemVerilog test only checks that the call
+// compiles and links.
+void* _pyhdl_if_PyTuple_GetItem(void* p0, unsigned long long idx) {
+    (void)p0;
+    (void)idx;
+    return 0;
+}
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/test_regress/t/t_dpi_inline_new.py b/test_regress/t/t_dpi_inline_new.py
new file mode 100755
index 000000000..d235c4eb3
--- /dev/null
+++ b/test_regress/t/t_dpi_inline_new.py
@@ -0,0 +1,19 @@
+#!/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')
+
+# Compile the SystemVerilog test with the DPI C stub.
+test.compile(v_flags2=["t/t_dpi_inline_new.cpp"])
+
+test.execute()
+
+test.passes()
diff --git a/test_regress/t/t_dpi_inline_new.v b/test_regress/t/t_dpi_inline_new.v
new file mode 100644
index 000000000..c14dc4927
--- /dev/null
+++ b/test_regress/t/t_dpi_inline_new.v
@@ -0,0 +1,51 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// 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
+
+package pyhdl_if;
+
+  typedef chandle PyObject;
+  import "DPI-C" context function PyObject _pyhdl_if_PyTuple_GetItem(input PyObject p0,
+                                    input longint unsigned p1);
+
+  function PyObject PyTuple_GetItem(input PyObject p0, input longint unsigned p1);
+    return _pyhdl_if_PyTuple_GetItem(p0, p1);
+  endfunction
+
+  class py_object;
+    function new(PyObject obj);
+    endfunction
+  endclass
+
+  class py_tuple;
+
+    function py_object get_item(int idx);
+      py_object ret = new(PyTuple_GetItem(null, longint'(idx)));
+      return ret;
+    endfunction
+
+  endclass
+
+endpackage
+
+module t (/*AUTOARG*/
+  // Inputs
+  clk
+  );
+  input clk;
+
+  import pyhdl_if::*;
+
+  initial begin
+    py_tuple t0 = new;
+    py_object o;
+    o = t0.get_item(1);
+    $write("*-* All Finished *-*\n");
+    $finish;
+  end
+
+endmodule