Fix internal error on bad widths (#3140) (#3145)

docs/CONTRIBUTORS

@@ -104,3 +104,4 @@ Yossi Nivin
 Yuri Victorovich
 Yutetsu TAKATSUKASA
 Yves Mathieu
+Zhanglei Wang

src/V3Const.cpp

@@ -1346,10 +1346,15 @@ private:
                        && (nodep->msbConst() > maxDeclBit || nodep->lsbConst() > maxDeclBit)) {
                 // See also warning in V3Width
                 // Must adjust by element width as declRange() is in number of elements
+                string msbLsbProtected;
+                if (nodep->declElWidth() == 0) {
+                    msbLsbProtected = "(nodep->declElWidth() == 0) " + std::to_string(nodep->msbConst()) + ":" + std::to_string(nodep->lsbConst());
+                } else {
+                    msbLsbProtected = std::to_string(nodep->msbConst() / nodep->declElWidth()) + ":" + std::to_string(nodep->lsbConst() / nodep->declElWidth());
+                }
                 nodep->v3warn(SELRANGE,
                               "Selection index out of range: "
-                                  << (nodep->msbConst() / nodep->declElWidth()) << ":"
-                                  << (nodep->lsbConst() / nodep->declElWidth()) << " outside "
+                                  << msbLsbProtected << " outside "
                                   << nodep->declRange().hiMaxSelect() << ":0"
                                   << (nodep->declRange().lo() >= 0
                                           ? ""

test_regress/t/t_bigmem_bad.out

@@ -0,0 +1,7 @@
+%Warning-SELRANGE: t/t_bigmem_bad.v:14:19: Selection index out of range: (nodep->declElWidth() == 0) -1:0 outside 268435455:0
+                                         : ... In instance t_bigmem
+   14 |       if (wen) mem[addr] <= data;
+      |                   ^
+                   ... For warning description see https://verilator.org/warn/SELRANGE?v=latest
+                   ... Use "/* verilator lint_off SELRANGE */" and lint_on around source to disable this message.
+%Error: Exiting due to

test_regress/t/t_bigmem_bad.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 2021 by filamoon. 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(linter => 1);
+
+lint(
+    fails => 1,
+    expect_filename => $Self->{golden_filename},
+    );
+
+ok(1);
+1;

test_regress/t/t_bigmem_bad.v

@@ -0,0 +1,16 @@
+// This test shall generate a warning, but not an internal error.
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2021 by Zhanglei Wang.
+// SPDX-License-Identifier: CC0-1.0
+module t_bigmem(
+   input wire clk,
+   input wire [27:0] addr,
+   input wire [255:0] data,
+   input wire wen
+);
+   reg [(1<<28)-1:0][255:0] mem;
+   always @(posedge clk) begin
+      if (wen) mem[addr] <= data;
+   end
+endmodule