Fix wrapping of string with control characters

Fix wrapping of string constants containing bytes 0-8, 11, 12 or 14-31
followed by a digit '0' to '7'.  We were emitting these bytes as a one
or two character octal escape sequence which when interpreted would
include the following character.

CHANGES.current

@@ -7,6 +7,12 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.3.0 (in progress)
 ===========================
 
+2024-08-01: olly
+	    Fix wrapping of string constants containing bytes 0-8, 11, 12 or
+	    14-31 followed by a digit '0' to '7'.  We were emitting these bytes
+	    as a one or two character octal escape sequence which when
+	    interpreted would include the following character.
+
 2024-07-27: olly
 	    #2087 Fix parsing of `noexcept` on a function pointer type used
 	    as the type of a function parameter.  We currently generate

Examples/test-suite/php/string_constants_runme.php

@@ -0,0 +1,18 @@
+<?php
+
+require "tests.php";
+
+// No new functions
+check::functions(array());
+// New classes
+check::classes(array('string_constants', 'things'));
+// New vars
+check::globals(array('AA3', 'EE3', 'ES3', 'QQ3', 'SS3', 'XX3', 'ZS3'));
+
+check::equal(string_constants::QQ1, "\01000!");
+check::equal(string_constants::QQ2, "\01000!");
+check::equal(QQ3_get(), "\01000!");
+$t = new things();
+check::equal($t->defarguments7(), "\01000!");
+
+check::done();

Examples/test-suite/string_constants.i

@@ -18,6 +18,7 @@
 #define XX1 "\x57\x58\x59"
 #define ZS1 "\0"
 #define ES1 ""
+#define QQ1 "\b00!"
 %}
 %constant SS2="ÆÎOU\n";
 %constant AA2="A\rB\nC";
@@ -25,6 +26,7 @@
 %constant XX2="\x57\x58\x59";
 %constant ZS2="\0";
 %constant ES2="";
+%constant QQ2="\b00!";
 
 %inline %{
 static const char *SS3 = "ÆÎOU\n";
@@ -33,6 +35,7 @@ static const char *EE3 = "\124\125\126";
 static const char *XX3 = "\x57\x58\x59";
 static const char *ZS3 = "\0";
 static const char *ES3 = "";
+static const char *QQ3 = "\b00!";
 struct things {
   const char * defarguments1(const char *SS4 = "ÆÎOU\n") { return SS4; }
   const char * defarguments2(const char *AA4 = "A\rB\nC") { return AA4; }
@@ -40,5 +43,6 @@ struct things {
   const char * defarguments4(const char *XX4 = "\x57\x58\x59") { return XX4; }
   const char * defarguments5(const char *ZS4 = "\0") { return ZS4; }
   const char * defarguments6(const char *ES4 = "") { return ES4; }
+  const char * defarguments7(const char *QQ4 = "\b00!") { return QQ4; }
 };
 %}

Source/Swig/misc.c

@@ -357,11 +357,9 @@ int Swig_storage_isstatic(Node *n) {
  * ----------------------------------------------------------------------------- */
 
 String *Swig_string_escape(String *s) {
-  String *ns;
-  int c;
-  ns = NewStringEmpty();
-
-  while ((c = Getc(s)) != EOF) {
+  String *ns = NewStringEmpty();
+  int c = Getc(s);
+  while (c != EOF) {
     if (c == '\n') {
       Printf(ns, "\\n");
     } else if (c == '\r') {
@@ -377,12 +375,21 @@ String *Swig_string_escape(String *s) {
     } else if (c == ' ') {
       Putc(c, ns);
     } else if (!isgraph(c)) {
+      int next_c = Getc(s);
       if (c < 0)
 	c += UCHAR_MAX + 1;
-      Printf(ns, "\\%o", c);
+      if (next_c >= '0' && next_c < '8') {
+	/* We need to emit 3 octal digits. */
+	Printf(ns, "\\%03o", c);
+      } else {
+	Printf(ns, "\\%o", c);
+      }
+      c = next_c;
+      continue;
     } else {
       Putc(c, ns);
     }
+    c = Getc(s);
   }
   return ns;
 }