RE: [XEN RFC PATCH 01/40] tools: Fix -Werror=maybe-uninitialized for xlu_pci_parse_bdf

[Wei Chen <Wei.Chen@xxxxxxx>]

Hi Jan,

> -----Original Message-----
> From: Jan Beulich <jbeulich@xxxxxxxx>
> Sent: 2021年8月11日 18:50
> To: Wei Chen <Wei.Chen@xxxxxxx>
> Cc: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>; xen-
> devel@xxxxxxxxxxxxxxxxxxxx; sstabellini@xxxxxxxxxx; julien@xxxxxxx
> Subject: Re: [XEN RFC PATCH 01/40] tools: Fix -Werror=maybe-uninitialized
> for xlu_pci_parse_bdf
> 
> On 11.08.2021 12:23, Wei Chen wrote:
> > | libxlu_pci.c: In function 'xlu_pci_parse_bdf':
> > | libxlu_pci.c:32:18: error: 'func' may be used uninitialized in this
> function [-Werror=maybe-uninitialized]
> > |    32 |     pcidev->func = func;
> > |       |     ~~~~~~~~~~~~~^~~~~~
> 
> I'm afraid I can't spot such an assignment in the file (nor the two
> similar ones further down). All I can see is
> 
>     pci->domain = domain;
>     pci->bus = bus;
>     pci->dev = dev;
>     pci->func = func;
> 

Sorry, I forgot to update my commit log with the latest code base.
I revert this change in my current code, I can't reproduce it.
I'm not sure if it's because I upgraded my build environment.
Give me sometime, if I can reproduce it I will update the commit
log in next version. If it's no longer needed, I will remove this
patch from this series.

> > | libxlu_pci.c:51:29: note: 'func' was declared here
> > |    51 |     unsigned dom, bus, dev, func, vslot = 0;
> > |       |                             ^~~~
> > | libxlu_pci.c:31:17: error: 'dev' may be used uninitialized in this
> function [-Werror=maybe-uninitialized]
> > |    31 |     pcidev->dev = dev;
> > |       |     ~~~~~~~~~~~~^~~~~
> > | libxlu_pci.c:51:24: note: 'dev' was declared here
> > |    51 |     unsigned dom, bus, dev, func, vslot = 0;
> > |       |                        ^~~
> > | libxlu_pci.c:30:17: error: 'bus' may be used uninitialized in this
> function [-Werror=maybe-uninitialized]
> > |    30 |     pcidev->bus = bus;
> > |       |     ~~~~~~~~~~~~^~~~~
> > | libxlu_pci.c:51:19: note: 'bus' was declared here
> > |    51 |     unsigned dom, bus, dev, func, vslot = 0;
> > |       |                   ^~~
> > | libxlu_pci.c:78:26: error: 'dom' may be used uninitialized in this
> function [-Werror=maybe-uninitialized]
> > |    78 |                 if ( dom & ~0xff )
> > |       |                      ~~~~^~~~~~~
> 
> I'm afraid I also can't spot a variable named "dom", nor a sufficiently
> similar if(). May I ask what code base these were observed with? Is the
> change needed at all anymore?
> 

same as above.

> > --- a/tools/libs/util/libxlu_pci.c
> > +++ b/tools/libs/util/libxlu_pci.c
> > @@ -15,7 +15,7 @@ static int parse_bdf(libxl_device_pci *pci, const char
> *str, const char **endp)
> >  {
> >      const char *ptr = str;
> >      unsigned int colons = 0;
> > -    unsigned int domain, bus, dev, func;
> > +    unsigned int domain = 0, bus = 0, dev = 0, func = 0;
> >      int n;
> >
> >      /* Count occurrences of ':' to detrmine presence/absence of the
> 'domain' */
> > @@ -28,7 +28,6 @@ static int parse_bdf(libxl_device_pci *pci, const char
> *str, const char **endp)
> >      ptr = str;
> >      switch (colons) {
> >      case 1:
> > -        domain = 0;
> >          if (sscanf(ptr, "%x:%x.%n", &bus, &dev, &n) != 2)
> >              return ERROR_INVAL;
> >          break;
> >
> 
> Also - which compiler did you encounter this with?
> 
> Finally please don't forget to Cc maintainers.
> 

If this patch still needed, I will do in next version.

> Jan