Hi Philippe,
I had put a descriptive message to make people aware that the pragma effects
the next line of code only. But I agree we can abbreviate it as per your
suggestion.
However, there is an ongoing discussion about an alternative (by which we could
avoid the pragma) on another thread at
https://edk2.groups.io/g/devel/message/59948.
Regards,
Sami Mujawar
-----Original Message-----
From: Philippe Mathieu-Daudé <phi...@redhat.com>
Sent: 20 May 2020 11:47 AM
To: Sami Mujawar <sami.muja...@arm.com>; devel@edk2.groups.io
Cc: Alexei Fedorov <alexei.fedo...@arm.com>; Ard Biesheuvel
<ard.biesheu...@arm.com>; l...@nuviainc.com; Matteo Carlini
<matteo.carl...@arm.com>; Laura Moretta <laura.more...@arm.com>; nd
<n...@arm.com>
Subject: Re: [PATCH v2 2/2] ArmPlatformPkg: Fix comparison of constants warning
Hi Sami,
On 5/18/20 2:46 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,
> 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.muja...@arm.com>
> ---
>
> 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..3c915e1e8de22a0b0b4cc46d495a
> 5a6cbc784013 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.'
We don't need to document how #pragma works each time we use it in the source
code...
What about a simpler comment, referring the particular Visual Studio
version:
//
// Disable 'potential comparison of a constant with another constant'
// warning with VS2017 compiler static code analysis option is enabled //
> +#pragma warning(suppress:6326)
> +#endif
> if (FixedPcdGet32 (PL011UartInteger) != 0) {
> Integer = FixedPcdGet32 (PL011UartInteger);
> Fractional = FixedPcdGet32 (PL011UartFractional);
>
-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#59955): https://edk2.groups.io/g/devel/message/59955
Mute This Topic: https://groups.io/mt/74289925/21656
Group Owner: devel+ow...@edk2.groups.io
Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com]
-=-=-=-=-=-=-=-=-=-=-=-
