From 13ddd0bc1cb598746dbfb24d5eb21973e1f3e0fa Mon Sep 17 00:00:00 2001
From: Wilson Snyder <wsnyder@wsnyder.org>
Date: Sun, 13 Jun 2021 12:38:31 -0400
Subject: [PATCH] Fix error on unsupported recursive functions (#2957).

---
 Changes                        |  2 +-
 src/V3LinkDot.cpp              | 16 +++++++++++-----
 test_regress/t/t_func_bad3.out |  5 +++++
 test_regress/t/t_func_bad3.pl  | 19 +++++++++++++++++++
 test_regress/t/t_func_bad3.v   | 15 +++++++++++++++
 5 files changed, 51 insertions(+), 6 deletions(-)
 create mode 100644 test_regress/t/t_func_bad3.out
 create mode 100755 test_regress/t/t_func_bad3.pl
 create mode 100644 test_regress/t/t_func_bad3.v

diff --git a/Changes b/Changes
index d1b63d9dc..70f794f7e 100644
--- a/Changes
+++ b/Changes
@@ -19,7 +19,7 @@ Verilator 4.205 devel
 **Minor:**
 
 * Merge const static data globally into a new constant pool (#3013). [Geza Lore]
-
+* Fix error on unsupported recursive functions (#2957). [Trefor Southwell]
 
 
 Verilator 4.204 2021-06-12
diff --git a/src/V3LinkDot.cpp b/src/V3LinkDot.cpp
index 102e92034..05469e928 100644
--- a/src/V3LinkDot.cpp
+++ b/src/V3LinkDot.cpp
@@ -2666,11 +2666,17 @@ private:
                 UINFO(7, "   ErrFtask curSymp=se" << cvtToHex(m_curSymp) << " dotSymp=se"
                                                   << cvtToHex(dotSymp) << endl);
                 if (foundp) {
-                    nodep->v3error("Found definition of '"
-                                   << m_ds.m_dotText << (m_ds.m_dotText == "" ? "" : ".")
-                                   << nodep->prettyName() << "'"
-                                   << " as a " << foundp->nodep()->typeName()
-                                   << " but expected a task/function");
+                    if (VN_IS(foundp->nodep(), Var) && m_ds.m_dotText == "" && m_ftaskp
+                        && m_ftaskp->name() == foundp->nodep()->name()) {
+                        nodep->v3warn(E_UNSUPPORTED, "Unsupported: Recursive function call "
+                                                         << nodep->prettyNameQ());
+                    } else {
+                        nodep->v3error("Found definition of '"
+                                       << m_ds.m_dotText << (m_ds.m_dotText == "" ? "" : ".")
+                                       << nodep->prettyName() << "'"
+                                       << " as a " << foundp->nodep()->typeName()
+                                       << " but expected a task/function");
+                    }
                 } else if (VN_IS(nodep, New) && m_statep->forPrearray()) {
                     // Resolved in V3Width
                 } else if (nodep->dotted() == "") {
diff --git a/test_regress/t/t_func_bad3.out b/test_regress/t/t_func_bad3.out
new file mode 100644
index 000000000..628c1a173
--- /dev/null
+++ b/test_regress/t/t_func_bad3.out
@@ -0,0 +1,5 @@
+%Error-UNSUPPORTED: t/t_func_bad3.v:12:27: Unsupported: Recursive function call 'recurse_self'
+   12 |       else recurse_self = recurse_self(i - 1) + 1;
+      |                           ^~~~~~~~~~~~
+                    ... For error description see https://verilator.org/warn/UNSUPPORTED?v=latest
+%Error: Exiting due to
diff --git a/test_regress/t/t_func_bad3.pl b/test_regress/t/t_func_bad3.pl
new file mode 100755
index 000000000..877e6133a
--- /dev/null
+++ b/test_regress/t/t_func_bad3.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 2003 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(
+    fails => $Self->{vlt_all},
+    expect_filename => $Self->{golden_filename},
+    );
+
+ok(1);
+1;
diff --git a/test_regress/t/t_func_bad3.v b/test_regress/t/t_func_bad3.v
new file mode 100644
index 000000000..9b8d672f0
--- /dev/null
+++ b/test_regress/t/t_func_bad3.v
@@ -0,0 +1,15 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2003 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+module t;
+
+   function recurse_self;
+      input i;
+      if (i == 0) recurse_self = 0;
+      else recurse_self = recurse_self(i - 1) + 1;
+   endfunction
+
+endmodule