Re: [PATCH] ShellPkg/Type.c: Add value check before (LoopVar - 1)

["Carsey, Jaben" <jaben.carsey@intel.com>]

Please remove the typo (there is an extra S after 'return'). This line:
// return Swith line feed for displaying each new line from left.


> -----Original Message-----
> From: Gao, Zhichao
> Sent: Monday, July 15, 2019 12:30 AM
> To: devel@edk2.groups.io
> Cc: Carsey, Jaben <jaben.carsey@intel.com>; Ni, Ray <ray.ni@intel.com>;
> Andrew Fish <afish@apple.com>
> Subject: [PATCH] ShellPkg/Type.c: Add value check before (LoopVar - 1)
> 
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1964
> 
> If the file begin with single line Feed ('\n'), then
> "AsciiChar == '\n' && ((CHAR8*)Buffer)[LoopVar-1] != '\r'"
> would cause a underflow. Add this condition
> "(AsciiChar == '\n' && LoopVar == 0)" before it to make sure
> (LoopVar - 1) would never encounter a underflow.
> 
> Cc: Jaben Carsey <jaben.carsey@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Andrew Fish <afish@apple.com>
> Signed-off-by: Zhichao Gao <zhichao.gao@intel.com>
> ---
>  ShellPkg/Library/UefiShellLevel3CommandsLib/Type.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/ShellPkg/Library/UefiShellLevel3CommandsLib/Type.c
> b/ShellPkg/Library/UefiShellLevel3CommandsLib/Type.c
> index 4efc0a8e24..c1f670c713 100644
> --- a/ShellPkg/Library/UefiShellLevel3CommandsLib/Type.c
> +++ b/ShellPkg/Library/UefiShellLevel3CommandsLib/Type.c
> @@ -78,12 +78,13 @@ TypeFileByHandle (
>            // Allow Line Feed (LF) (0xA) & Carriage Return (CR) (0xD)
>            // characters to be displayed as is.
>            //
> -          if (AsciiChar == '\n' && ((CHAR8*)Buffer)[LoopVar-1] != '\r') {
> +          if ((AsciiChar == '\n' && LoopVar == 0) ||
> +              (AsciiChar == '\n' && ((CHAR8*)Buffer)[LoopVar-1] != '\r')) {
>              //
> -            // In case Line Feed (0xA) is encountered & Carriage Return (0xD)
> -            // was not the previous character, print CR and LF. This is because
> -            // Shell 2.0 requires carriage return with line feed for displaying
> -            // each new line from left.
> +            // In case file begin with single line Feed or Line Feed (0xA) is
> +            // encountered & Carriage Return (0xD) was not previous character,
> +            // print CR and LF. This is because Shell 2.0 requires carriage
> +            // return Swith line feed for displaying each new line from left.
>              //
>              ShellPrintEx (-1, -1, L"\r\n");
>              continue;
> --
> 2.21.0.windows.1