Re: [edk2-devel] [PATCH v2 2/5] MdeModulePkg/Bus/Pci/PciBusDxe: Fix MISSING_BREAK Coverity issues

["Michael D Kinney" <michael.d.kinney@intel.com>]

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Hi Ranbir,

Ignoring false positive in static analysis tools is typically a burden.

It is better to avoid false positives with code changes as long as the code changes do not make the implementation confusing and hard to maintain.

I think depending on fall through case statements is confusing and removing them will make the code easier to understand and maintain.

Mike

From: Ranbir Singh <rsingh@ventanamicro.com>
Sent: Tuesday, November 7, 2023 7:51 PM
To: Kinney, Michael D <michael.d.kinney@intel.com>
Cc: devel@edk2.groups.io; lersek@redhat.com; Ni, Ray <ray.ni@intel.com>; Veeresh Sangolli <veeresh.sangolli@dellteam.com>
Subject: Re: [edk2-devel] [PATCH v2 2/5] MdeModulePkg/Bus/Pci/PciBusDxe: Fix MISSING_BREAK Coverity issues

As mentioned in the commit message, the comment helps in making it explicit and evident that the missing break is not a human miss, but intentional.
Hence, the comment should be considered as being added for the human code readers / developers.

So even if some static analysis tool flags such an issue, it can be fairly easy now to ignore that on manual inspection. If desired this can also be stated in the comment itself like -

+                  //
+                  // No break here as this is an intentional fall through.
+                  // Ignore any static tool issue if pointed.
+                  //

Yes, there can be other solutions (which may or may not be worth the effort), but for now I went with the least code change approach.

On Tue, Nov 7, 2023 at 11:29 PM Kinney, Michael D <michael.d.kinney@intel.com<mailto:michael.d.kinney@intel.com>> wrote:
This comment style only works with Coverity.

Other static analysis tools may flag the same issue again.

It is better to update the logic so no static analysis tool will
flag this issue.

Mike

> -----Original Message-----
> From: devel@edk2.groups.io<mailto:devel@edk2.groups.io> <devel@edk2.groups.io<mailto:devel@edk2.groups.io>> On Behalf Of Laszlo
> Ersek
> Sent: Tuesday, November 7, 2023 8:23 AM
> To: devel@edk2.groups.io<mailto:devel@edk2.groups.io>; rsingh@ventanamicro.com<mailto:rsingh@ventanamicro.com>
> Cc: Ni, Ray <ray.ni@intel.com<mailto:ray.ni@intel.com>>; Veeresh Sangolli
> <veeresh.sangolli@dellteam.com<mailto:veeresh.sangolli@dellteam.com>>
> Subject: Re: [edk2-devel] [PATCH v2 2/5]
> MdeModulePkg/Bus/Pci/PciBusDxe: Fix MISSING_BREAK Coverity issues
>
> On 11/7/23 07:19, Ranbir Singh wrote:
> > From: Ranbir Singh <Ranbir.Singh3@Dell.com<mailto:Ranbir.Singh3@Dell.com>>
> >
> > The function UpdatePciInfo has switch-case code in which there are
> fall
> > through from case 32: to case 64:. While this is seeemingly
> intentional,
> > it is not evident to any general code reader why there is no break;
> in
> > between. Adding
> >
> >     // No break; here as this is an intentional fallthrough.
> >
> > as comment in between makes it explicit. Incidentally, the comment
> > satisfies Coverity as well.
> >
> > REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4239
> >
> > Cc: Ray Ni <ray.ni@intel.com<mailto:ray.ni@intel.com>>
> > Co-authored-by: Veeresh Sangolli <veeresh.sangolli@dellteam.com<mailto:veeresh.sangolli@dellteam.com>>
> > Signed-off-by: Ranbir Singh <Ranbir.Singh3@Dell.com<mailto:Ranbir.Singh3@Dell.com>>
> > Signed-off-by: Ranbir Singh <rsingh@ventanamicro.com<mailto:rsingh@ventanamicro.com>>
> > ---
> >  MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c
> b/MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c
> > index 6594b8eae83f..eda97285ee18 100644
> > --- a/MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c
> > +++ b/MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c
> > @@ -1428,6 +1428,9 @@ UpdatePciInfo (
> >                switch (Ptr->AddrSpaceGranularity) {
> >                  case 32:
> >                    PciIoDevice->PciBar[BarIndex].BarType =
> PciBarTypeMem32;
> > +                  //
> > +                  // No break; here as this is an intentional fall
> through.
> > +                  //
> >                  case 64:
> >                    PciIoDevice->PciBar[BarIndex].BarTypeFixed =
> TRUE;
> >                    break;
> > @@ -1440,6 +1443,9 @@ UpdatePciInfo (
> >                switch (Ptr->AddrSpaceGranularity) {
> >                  case 32:
> >                    PciIoDevice->PciBar[BarIndex].BarType =
> PciBarTypePMem32;
> > +                  //
> > +                  // No break; here as this is an intentional fall
> through.
> > +                  //
> >                  case 64:
> >                    PciIoDevice->PciBar[BarIndex].BarTypeFixed =
> TRUE;
> >                    break;
>
> Agree, but the semicolon's placement is awkward. I propose
>
>   No break here, as this is an intentional fall through.
>
> Reviewed-by: Laszlo Ersek <lersek@redhat.com<mailto:lersek@redhat.com>>
>
>
>
> 
>


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