From a5ffcd0a55800105d7b9c87de6bfbb3aeaae19fa Mon Sep 17 00:00:00 2001
From: jean-pierre charras <jp.charras@wanadoo.fr>
Date: Sun, 28 Jan 2024 16:07:52 +0100
Subject: [PATCH] void Prettify(): fix a bug in a corner case, when a string
 ends with '\' A '\' in a string is encoded as \\. A '"' in a string is
 encoded as \". But prettify parser did not take in account a string encoded
 as "xx\\" (for xx\) So we need to verify if a sequence is xx\" or xx\\", i.e.
 if there are a odd count of backslashes before a '"' Fixes #16777
 https://gitlab.com/kicad/code/kicad/-/issues/16777

---
 common/io/kicad/kicad_io_utils.cpp | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/common/io/kicad/kicad_io_utils.cpp b/common/io/kicad/kicad_io_utils.cpp
index a6648ed374..6bca79dc48 100644
--- a/common/io/kicad/kicad_io_utils.cpp
+++ b/common/io/kicad/kicad_io_utils.cpp
@@ -1,7 +1,7 @@
 /*
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
- * Copyright (C) 2023 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 2024 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software: you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the
@@ -90,6 +90,7 @@ void Prettify( std::string& aSource, char aQuoteChar )
     bool inMultiLineList = false;
     bool inXY = false;
     int  column = 0;
+    int  backslashCount = 0;    // Count of successive backslash read since any other char
 
     auto isWhitespace = []( const char aChar )
             {
@@ -207,12 +208,16 @@ void Prettify( std::string& aSource, char aQuoteChar )
             }
             else
             {
-                // The output formatter escapes double-quotes
-                if( *cursor == aQuoteChar
-                    && ( cursor == aSource.begin() || *( cursor - 1 ) != '\\' ) )
-                {
+                // The output formatter escapes double-quotes (like \")
+                // But a corner case is a sequence like \\"
+                // therefore a '\' is attached to a '"' if a odd number of '\' is detected
+                if( *cursor == '\\' )
+                    backslashCount++;
+                else if( *cursor == aQuoteChar && ( backslashCount & 1 ) == 0 )
                     inQuote = !inQuote;
-                }
+
+                if( *cursor != '\\' )
+                    backslashCount = 0;
 
                 formatted.push_back( *cursor );
                 column++;