Re: [PATCH v2 2/2] ArmPlatformPkg: Fix comparison of constants warning

["Leif Lindholm" <leif@nuviainc.com>]

On Mon, May 18, 2020 at 13:46:46 +0100, 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, and disabling it
> case by case is a suitable option.
> 
> Therefore, disable this warning for Visual studio
> compilers using the pragma suppress directive that:
> 'Pushes the current state of the pragma on the stack,
> disables the specified warning for the next line, and
> then pops the warning stack so that the pragma state
> is reset.'
> 
> Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>

Reviewed-by: Leif Lindholm <leif@nuviainc.com>

However, this patch set is garbled. The cover-letter claims to be v3,
1/2 claims to be v1-resend and 2/2 claims to be v2.
Please use git format-patch for generating your patches before sending
out - that will do the right thing.

/
    Leif

> ---
> 
> Notes:
>     v2:
>      - Update patch to selectively suppress comparison of         [SAMI]
>        constant warning and submit as a separate series.
>     
>     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 | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/ArmPlatformPkg/Library/PL011UartLib/PL011UartLib.c b/ArmPlatformPkg/Library/PL011UartLib/PL011UartLib.c
> index 2d3c279cce49304959953ec4a34b50e09a7d0045..3c915e1e8de22a0b0b4cc46d495a5a6cbc784013 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
>  
> @@ -174,6 +174,14 @@ PL011UartInitializePort (
>    //
>  
>    // If PL011 Integer value has been defined then always ignore the BAUD rate
> +#if defined(_MSC_EXTENSIONS)
> +  // Suppress 'warning C6326' reported by Visual Studio compiler using
> +  // the suppress pragma directive that: 'Pushes the current state of
> +  // the pragma on the stack, disables the specified warning for the
> +  // next line, and then pops the warning stack so that the pragma state
> +  // is reset.'
> +#pragma warning(suppress:6326)
> +#endif
>    if (FixedPcdGet32 (PL011UartInteger) != 0) {
>      Integer = FixedPcdGet32 (PL011UartInteger);
>      Fractional = FixedPcdGet32 (PL011UartFractional);



> -- 
> 'Guid(CE165669-3EF3-493F-B85D-6190EE5B9759)'
>