From 9ff3407c60d9b3c57c2f49eb8c05d192fb64df56 Mon Sep 17 00:00:00 2001
From: Stephen Heumann <stephenheumann@gmail.com>
Date: Sat, 1 Sep 2018 16:11:18 -0500
Subject: [PATCH] Avoid producing invalid string literals in #pragma expand
 output.

Previously, the characters ", /, and ? within string literals were not escaped in #pragma expand output, which could result in them being erroneously interpreted as ending the string literal, starting an escape sequence, or being part of a trigraph (respectively). Also, escape sequences were output in hexadecimal format. Since there is no length limit on hexadecimal escape sequences, this could result in subsequent characters in the string being interpreted as part of the escape sequence.

This fixes the issues by escaping the characters ", /, and ?, and by using three-digit octal escape sequences rather than hexadecimal ones.
---
 Scanner.pas | 31 +++++++++----------------------
 1 file changed, 9 insertions(+), 22 deletions(-)

diff --git a/Scanner.pas b/Scanner.pas
index 7505be5..a07f87a 100644
--- a/Scanner.pas
+++ b/Scanner.pas
@@ -659,23 +659,6 @@ var
    ch: char;                            {work character}
    i: integer;                          {loop counter}
 
-
-   procedure PrintHexDigit(i: integer);
-
-   { Print a digit as a hex character                           }
-   {                                                            }
-   { Parameters:                                                }
-   {    i: value to print in least significant 4 bits           }
-
-   begin {PrintHexDigit}
-   i := i & $000F;
-   if i < 10 then
-      write(chr(i | ord('0')))
-   else
-      write(chr(i + ord('A') - 10));
-   end; {PrintHexDigit}
-
-
 begin {PrintToken}
 case token.kind of
    typedef,
@@ -693,12 +676,16 @@ case token.kind of
                      write('"');
                      for i := 1 to token.sval^.length do begin
                         ch := token.sval^.str[i];
-                        if ch in [' '..'~'] then
-                           write(ch)
+                        if ch in [' '..'~'] then begin
+                           if ch in ['"','\','?'] then
+                              write('\');
+                           write(ch);
+                           end {if}
                         else begin
-                           write('\x0');
-                           PrintHexDigit(ord(ch)>>4);
-                           PrintHexDigit(ord(ch));
+                           write('\');
+                           write((ord(ch)>>6):1);
+                           write(((ord(ch)>>3) & $0007):1);
+                           write((ord(ch) & $0007):1);
                            end; {else}
                         end; {for}
                      write('"');