From 49c3e5d553ee8c98761671e62a3b709873605374 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ivan=20Ust=C3=BB=C5=BEanin?= <profic@gmail.com>
Date: Sat, 25 Sep 2021 11:55:57 +0300
Subject: [PATCH] UDL lexer: fix potential infinite loop

Fixed a condition in a loop which is always true (unsigned >= 0) and can
potentially turn the loop infinite.

And removed a check after the loop which now is also always false.

Close #10597
---
 scintilla/lexers/LexUser.cxx | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/scintilla/lexers/LexUser.cxx b/scintilla/lexers/LexUser.cxx
index 8bedc6196..a133a27db 100644
--- a/scintilla/lexers/LexUser.cxx
+++ b/scintilla/lexers/LexUser.cxx
@@ -786,20 +786,20 @@ static inline void ReColoringCheck(Sci_PositionU & startPos, int & nestedLevel,
                                    int & isCommentLine, bool & isInComment, Accessor & styler, vector<nestedInfo> & lastNestedGroup,
                                    vector<nestedInfo> & nestedVector, /* vector<int> & foldVector, */ int & continueCommentBlock)
 {
-    // re-coloring always starts at line beginning !!
-
-    // special exception for multipart keywords
-    initStyle = styler.StyleAt(startPos-1); // check style of previous new line character
-    if ( (initStyle >= SCE_USER_STYLE_KEYWORD1 && initStyle < (SCE_USER_STYLE_KEYWORD1+SCE_USER_TOTAL_KEYWORD_GROUPS))    // keywords1-8
-          || initStyle == SCE_USER_STYLE_FOLDER_IN_COMMENT
-          || initStyle == SCE_USER_STYLE_FOLDER_IN_CODE2 )
+    if (startPos > 0)
     {
-        // we are in middle of multi-part keyword that contains newline characters, go back until current style ends
-        while (startPos >= 0 && styler.StyleAt(--startPos) == initStyle);
-    }
+        // re-coloring always starts at line beginning !!
 
-    if (static_cast<int>(startPos) < 0)
-        startPos = 0;
+        // special exception for multipart keywords
+        initStyle = styler.StyleAt(startPos-1); // check style of previous new line character
+        if ( (initStyle >= SCE_USER_STYLE_KEYWORD1 && initStyle < (SCE_USER_STYLE_KEYWORD1+SCE_USER_TOTAL_KEYWORD_GROUPS))    // keywords1-8
+              || initStyle == SCE_USER_STYLE_FOLDER_IN_COMMENT
+              || initStyle == SCE_USER_STYLE_FOLDER_IN_CODE2 )
+        {
+            // we are in middle of multi-part keyword that contains newline characters, go back until current style ends
+            while (startPos > 0 && styler.StyleAt(--startPos) == initStyle);
+        }
+    }
 
     if (startPos > 0)
     {
@@ -808,8 +808,6 @@ static inline void ReColoringCheck(Sci_PositionU & startPos, int & nestedLevel,
         do
         {
             ch = styler.SafeGetCharAt(--startPos);
-            if (startPos == -1)
-                startPos = 0;
         }
         while(ch != '\r' && ch != '\n' && startPos > 0);