Fix recursive display causing segfault (#4480).

Changes

@@ -50,6 +50,7 @@ Verilator 5.015 devel
 * Fix error on enum with VARHIDDEN of cell (#4482). [Michail Rontionov]
 * Fix lint of case statements with enum and wildcard bits (#4464) (#4487). [Anthony Donlon]
 * Fix reference to extended class in parameterized class (#4466).
+* Fix recursive display causing segfault (#4480). [Kuoping Hsu]
 * Fix the error message when the type of ref argument is wrong (#4490). [Ryszard Rozak, Antmicro Ltd]
 * Fix display %x formatting of real.
 * Fix mis-warning on #() in classes' own functions.

src/V3EmitCFunc.cpp

@@ -314,6 +314,7 @@ void EmitCFunc::displayNode(AstNode* nodep, AstScopeName* scopenamep, const stri
 
     // Convert Verilog display to C printf formats
     //          "%0t" becomes "%d"
+    VL_RESTORER(m_emitDispState);
     m_emitDispState.clear();
     string vfmt;
     string::const_iterator pos = vformat.begin();

test_regress/t/t_display_recurse.out

@@ -0,0 +1,9 @@
+          0: 0000dead
+          4: 0001dead
+          8: 0002dead
+         12: 0003dead
+         16: 0004dead
+         20: 0005dead
+         24: 0006dead
+         28: 0007dead
+*-* All Finished *-*

test_regress/t/t_display_recurse.pl

@@ -0,0 +1,22 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2023 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(
+    );
+
+execute(
+    expect_filename => $Self->{golden_filename},
+    check_finished => 1,
+    );
+
+ok(1);
+1;

test_regress/t/t_display_recurse.v

@@ -0,0 +1,52 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2023 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+module t(/*AUTOARG*/
+   // Inputs
+   clk
+   );
+   input clk;
+
+   integer i;
+   integer count = 'd0;
+
+   always @(posedge clk) begin
+      count <= count + 1;
+      if (count == 10) begin
+         for(i=0; i<30; i=i+4) begin
+            // See issue #4480, verilator may inline getb() which has another display inside it
+            $display("%d: %02x%02x%02x%02x", i, getb(i+3), getb(i+2), getb(i+1), getb(i));
+         end
+      end
+      if (count == 11) begin
+         $write("*-* All Finished *-*\n");
+         $finish;
+      end
+   end
+
+   localparam SIZE = 64*1024;
+   localparam ADDRW = $clog2(SIZE/4);
+   reg [31: 0] ram [(SIZE/4)-1: 0];
+
+   function [7:0] getb;
+      input [31:0] address;
+      if (address[31:ADDRW+2] != 0) begin
+         $display("Address out of range");
+      end
+      case(address[1:0])
+        0: getb = ram[address[ADDRW+1: 2]][8*0+7:8*0];
+        1: getb = ram[address[ADDRW+1: 2]][8*1+7:8*1];
+        2: getb = ram[address[ADDRW+1: 2]][8*2+7:8*2];
+        3: getb = ram[address[ADDRW+1: 2]][8*3+7:8*3];
+      endcase
+   endfunction
+
+   initial begin
+      for (i=0; i<SIZE/4; i=i+1) begin
+         ram[i] = {i[15:0], 16'hdead};
+      end
+   end
+endmodule