Re: [PATCH 1/2] MdeModulePkg/PciBusDxe: Prevent truncating constant values.

["Marvin Häuser" <Marvin.Haeuser@outlook.com>]

Hello Andrew,

Thanks for your input. I already submitted a patch to do that: "[edk2] [PATCH 1/2] MdePkg/Base.h: Ensure safe bitwise operations."
Would be great if you took a look.

Thanks,
Marvin.

From: afish@apple.com <afish@apple.com>
Sent: Tuesday, February 27, 2018 7:50 PM
To: Laszlo Ersek <lersek@redhat.com>
Cc: Marvin Häuser <Marvin.Haeuser@outlook.com>; edk2-devel@lists.01.org; ruiyu.ni@intel.com; eric.dong@intel.com; star.zeng@intel.com
Subject: Re: [edk2] [PATCH 1/2] MdeModulePkg/PciBusDxe: Prevent truncating constant values.




On Feb 27, 2018, at 10:42 AM, Laszlo Ersek <lersek@redhat.com<mailto:lersek@redhat.com>> wrote:

On 02/27/18 17:49, Marvin Häuser wrote:

The toolcahin VS2015x86 issues warnings when truncating constant
values. Explicitely cast such to avoid it.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Marvin Haeuser <Marvin.Haeuser@outlook.com<mailto:Marvin.Haeuser@outlook.com>>
---
MdeModulePkg/Bus/Pci/PciBusDxe/PciResourceSupport.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/MdeModulePkg/Bus/Pci/PciBusDxe/PciResourceSupport.c b/MdeModulePkg/Bus/Pci/PciBusDxe/PciResourceSupport.c
index 2f713fcee95e..a752853f3e9e 100644
--- a/MdeModulePkg/Bus/Pci/PciBusDxe/PciResourceSupport.c
+++ b/MdeModulePkg/Bus/Pci/PciBusDxe/PciResourceSupport.c
@@ -1936,7 +1936,7 @@ ProgramP2C (
                   &BridgeControl
                   );

-      BridgeControl &= (UINT16) ~PCI_CARD_PREFETCHABLE_MEMORY_0_ENABLE;
+      BridgeControl &= (UINT16) ~(UINT16)PCI_CARD_PREFETCHABLE_MEMORY_0_ENABLE;
      PciIo->Pci.Write (
                   PciIo,
                   EfiPciIoWidthUint16,
@@ -2005,7 +2005,7 @@ ProgramP2C (
                   &BridgeControl
                   );

-      BridgeControl &= (UINT16) ~(PCI_CARD_PREFETCHABLE_MEMORY_1_ENABLE);
+      BridgeControl &= (UINT16) ~(UINT16)(PCI_CARD_PREFETCHABLE_MEMORY_1_ENABLE);
      PciIo->Pci.Write (
                   PciIo,
                   EfiPciIoWidthUint16,

My recommendation is the same as for:

 [edk2] [PATCH 2/2] MdeModulePkg/BaseSerialPortLib16550: Prevent
                    truncating constant values.

#define PCI_CARD_PREFETCHABLE_MEMORY_0_ENABLE BIT8
#define PCI_CARD_PREFETCHABLE_MEMORY_1_ENABLE BIT9

#define  BIT8     0x00000100
#define  BIT9     0x00000200


Laszlo,

Stupid question? Would making BIT8 0x00000100U help? I notice we use ULL for the larger ones, and I don't remember why we don't use U for the ones that fit into a int?

Thanks,

Andrew Fish


So I suggest (UINT32) for the casts.


I'd also suggest a better subject line / commit message. Can we say:

 Package/Module: avoid bit-negating signed integer constants

and then the commit message could quote the VS2015x86 warnings.

Again, just my two cents; I defer to the MdeModulePkg maintainers.

Thanks!
Laszlo
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