Shellpkg/editor: Fix a bug that may modifies Line[-1]

The original code as below intend to set the character
before last column to CHAR_NULL.
  Line[(LastCol % (ARRAY_SIZE (Line) - 1)) - 1] = CHAR_NULL;

But when LastCol % (ARRAY_SIZE (Line) - 1)) equals to 0,
Line[-1] is modified.

We should change to code as below:
  Line[(LastCol - 1) % (ARRAY_SIZE (Line) - 1)] = CHAR_NULL;

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>
Reviewed-by: Hao A Wu <hao.a.wu@intel.com>

diff --git a/ShellPkg/Library/UefiShellDebug1CommandsLib/UefiShellDebug1CommandsLib.c b/ShellPkg/Library/UefiShellDebug1CommandsLib/UefiShellDebug1CommandsLib.c
index d26d08f95c14c365ce2c6990eb55681172978950..b45e9a33f393529bfbb33ef9715c108d43e5e232 100644 (file)
--- a/ShellPkg/Library/UefiShellDebug1CommandsLib/UefiShellDebug1CommandsLib.c
+++ b/ShellPkg/Library/UefiShellDebug1CommandsLib/UefiShellDebug1CommandsLib.c
@@ -205,7 +205,7 @@ EditorClearLine (
         //\r
         // if CHAR_NULL is still at position LastCol, it will cause first line error\r
         //\r
-        Line[(LastCol % (ARRAY_SIZE (Line) - 1)) - 1] = CHAR_NULL;\r
+        Line[(LastCol - 1) % (ARRAY_SIZE (Line) - 1)] = CHAR_NULL;\r
       } else {\r
         Line[LastCol % (ARRAY_SIZE (Line) - 1)] = CHAR_NULL;\r
       }\r