From a595916574dc3992797340fc257b634456b364ca Mon Sep 17 00:00:00 2001
From: Daniel Kroening <dkr@amazon.com>
Date: Wed, 15 Oct 2025 07:51:50 -0700
Subject: [PATCH] Verilog: KNOWNBUG test for unconnected module input ports

---
 .../verilog/modules/unconnected_ports1.desc   |  8 ++++++
 .../verilog/modules/unconnected_ports1.sv     | 25 +++++++++++++++++++
 2 files changed, 33 insertions(+)
 create mode 100644 regression/verilog/modules/unconnected_ports1.desc
 create mode 100644 regression/verilog/modules/unconnected_ports1.sv

diff --git a/regression/verilog/modules/unconnected_ports1.desc b/regression/verilog/modules/unconnected_ports1.desc
new file mode 100644
index 000000000..e45992263
--- /dev/null
+++ b/regression/verilog/modules/unconnected_ports1.desc
@@ -0,0 +1,8 @@
+KNOWNBUG
+unconnected_ports1.v
+--bound 0
+^EXIT=0$
+^SIGNAL=0$
+--
+--
+This fails an assertion.
diff --git a/regression/verilog/modules/unconnected_ports1.sv b/regression/verilog/modules/unconnected_ports1.sv
new file mode 100644
index 000000000..27562a2e9
--- /dev/null
+++ b/regression/verilog/modules/unconnected_ports1.sv
@@ -0,0 +1,25 @@
+module my_module(input [31:0] x, y, z = 5);
+
+endmodule
+
+module main();
+
+  my_module m1(.x(1), .y(), .z());
+
+  // 1800-2017 23.3.3.2 says
+  // "If left unconnected, the port shall have the default
+  // initial value corresponding to the data type."
+  // This is 'x for logic types.
+  // However, Icarus Verilog, VCS, Questa, Xcelium use 'z.
+
+  initial assert (m1.x == 1);
+  initial assert (m1.y === 'z);
+  initial assert (m1.z == 5);
+
+  my_module m2(/* blank */, 1, /* blank */);
+
+  initial assert (m2.x === 'z);
+  initial assert (m2.y == 1);
+  initial assert (m2.z == 5);
+
+endmodule