Fix decoding octal string escapes with 1-2 digits (#6108).

Changes

@@ -68,6 +68,7 @@ Verilator 5.037 devel
 * Fix casting reals to large integrals (#6085). [Todd Strader]
 * Fix nested hier blocks workers error (#6087). [Bartłomiej Chmiel, Antmicro Ltd.]
 * Fix `--lib-create` with double-underscore (#6099).
+* Fix decoding octal string escapes with 1-2 digits (#6108).
 
 
 Verilator 5.036 2025-04-27

src/V3String.cpp

@@ -160,16 +160,18 @@ string VString::unquoteSVString(const string& text, string& errOut) {
             if (std::isdigit(*cp)) {
                 octal_val = octal_val * 8 + (*cp - '0');
                 if (++octal_digits == 3) {
-                    octal_digits = 0;
-                    quoted = false;
                     newtext += octal_val;
+                    octal_digits = 0;
+                    octal_val = 0;
+                    quoted = false;
                 }
             } else {
                 if (octal_digits) {
                     // Spec allows 1-3 digits
-                    octal_digits = 0;
-                    quoted = false;
                     newtext += octal_val;
+                    octal_digits = 0;
+                    octal_val = 0;
+                    quoted = false;
                     --cp;  // Backup to reprocess terminating character as non-escaped
                     continue;
                 }
@@ -200,6 +202,11 @@ string VString::unquoteSVString(const string& text, string& errOut) {
                 }
             }
         } else if (*cp == '\\') {
+            if (octal_digits) {
+                newtext += octal_val;
+                octal_digits = 0;
+                octal_val = 0;
+            }
             quoted = true;
             octal_digits = 0;
         } else {

test_regress/t/t_string_octal.py

@@ -0,0 +1,18 @@
+#!/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')
+
+test.compile()
+
+test.execute()
+
+test.passes()

test_regress/t/t_string_octal.v

@@ -0,0 +1,43 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// 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
+
+`define stop $stop
+`define checko(gotv,expv) do if ((gotv) !== (expv)) begin $write("%%Error: %s:%0d:  got='h%x exp='h%x\n", `__FILE__,`__LINE__, (gotv), (expv)); `stop; end while(0);
+
+module t;
+   string s;
+   initial begin
+      s = $sformatf("\099 \119 \121"); // Q Q Q
+      // $display("%o %o %o %o %o", s[0], s[1], s[2], s[3], s[4]);
+      // Results vary by simulator.  Some possibilities:
+      // 0 0 0 0 0
+      // 40 71 71 40 11
+      // 71 71 40 11 071
+
+      s = $sformatf("\088 \108 \110"); // H H H
+      // $display("%o %o %o %o %o", s[0], s[1], s[2], s[3], s[4]);
+      // Results vary by simulator.  Some possibilities:
+      // 0 0 0 0 0
+      // 40 70 70 40 10
+      // 70 70 40 10 70
+
+      s = $sformatf("\102\3\12."); // B\023\312.
+      // $display("%o %o %o %o %o", s[0], s[1], s[2], s[3], s[4]);
+      `checko(s[0], 8'o102);
+      `checko(s[1], 8'o003);
+      `checko(s[2], 8'o012);
+      `checko(s[3], 8'o056);
+
+      s = $sformatf("\102.\3.\12\103"); // B.\023.C
+      // $display("%o %o %o %o %o", s[0], s[1], s[2], s[3], s[4]);
+      `checko(s[0], 8'o102);
+      `checko(s[2], 8'o003);
+      `checko(s[4], 8'o012);
+      `checko(s[5], 8'o103);
+      $display("*-* All Finished *-*");
+      $finish;
+   end
+endmodule