[edk2-devel] [PATCH v3 2/2] ArmPlatformPkg: Fix comparison of constants warning

[Philippe Mathieu-Daudé]

On 5/21/20 5:20 PM, Sami Mujawar wrote:
> The VS2017 compiler reports 'warning C6326: potential
> comparison of a constant with another constant' when
> a fixed PCD value is compared with a constant value.
> 
> The faulting code is as marked by '-->' below:
> 
> --> if (FixedPcdGet32 (PL011UartInteger) != 0) {
>        Integer = FixedPcdGet32 (PL011UartInteger);
>        Fractional = FixedPcdGet32 (PL011UartFractional);
>      } else {
>      ...
> 
> The macro FixedPcdGet32 (PL011UartInteger) evaluates
> to a macro _PCD_VALUE_PL011UartInteger that is defined
> by the build system to represent the UART Integer
> value. Therefore, the VS2017 compiler reports the above
> warning.
> 
> In this case the warning reported by the Visual Studio
> compiler does not evaluate to an issue. However, it can
> be useful to detect potential issues in other scenarios.
> Other compilers may either be incapable of detecting and
> reporting comparison with constant warnings or may be
> good at reducing false positives. So, it is definitely
> useful to keep this warning enabled.
> 
> Therefore, slight adjustments are made to the code to
> stop Visual Studio from reporting this warning.
> 
> Signed-off-by: Sami Mujawar <sami.mujawar at arm.com>
> ---
> 
> Notes:
>      v3:
>       - Adjusted code to fix warning instead of using a pragma     [SAMI]
>      
>      v2:
>       - Update patch to selectively suppress comparison of         [SAMI]
>         constant warning and submit as a separate series.
>       - Feedback and discussion can be seen at
>         https://edk2.groups.io/g/devel/topic/74289925
>      
>      v1:
>       - Fix comparison of constant warning reported by VS2017      [SAMI]
>       - Various feedbacks can be seen at:
>         https://edk2.groups.io/g/devel/topic/32999801#46278
> 
>   ArmPlatformPkg/Library/PL011UartLib/PL011UartLib.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/ArmPlatformPkg/Library/PL011UartLib/PL011UartLib.c b/ArmPlatformPkg/Library/PL011UartLib/PL011UartLib.c
> index 2d3c279cce49304959953ec4a34b50e09a7d0045..d710fd3e3c8e700915d20cb4a980f51b3e078d16 100644
> --- a/ArmPlatformPkg/Library/PL011UartLib/PL011UartLib.c
> +++ b/ArmPlatformPkg/Library/PL011UartLib/PL011UartLib.c
> @@ -2,7 +2,7 @@
>     Serial I/O Port library functions with no library constructor/destructor
>   
>     Copyright (c) 2008 - 2010, Apple Inc. All rights reserved.<BR>
> -  Copyright (c) 2011 - 2019, ARM Ltd. All rights reserved.<BR>
> +  Copyright (c) 2011 - 2020, ARM Ltd. All rights reserved.<BR>
>   
>     SPDX-License-Identifier: BSD-2-Clause-Patent
>   
> @@ -174,8 +174,8 @@ PL011UartInitializePort (
>     //
>   
>     // If PL011 Integer value has been defined then always ignore the BAUD rate
> -  if (FixedPcdGet32 (PL011UartInteger) != 0) {
> -    Integer = FixedPcdGet32 (PL011UartInteger);
> +  Integer = FixedPcdGet32 (PL011UartInteger);
> +  if (Integer != 0) {

Simple, lovely :)

Reviewed-by: Philippe Mathieu-Daude <philmd at redhat.com>

>       Fractional = FixedPcdGet32 (PL011UartFractional);
>     } else {
>       // If BAUD rate is zero then replace it with the system default value
> 


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