Re: [Qemu-devel] [PULL v3 03/21] ppc: switch to constants within BUILD_BUG_ON

[Michael S. Tsirkin]

On Wed, Feb 01, 2017 at 09:16:28AM +1100, David Gibson wrote:
> On Tue, Jan 31, 2017 at 03:14:29PM +0200, Michael S. Tsirkin wrote:
> > We are switching BUILD_BUG_ON to verify that it's parameter is a
> > compile-time constant, and it turns out that some gcc versions
> > (specifically gcc (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609) are
> > not smart enough to figure it out for expressions involving local
> > variables. This is harmless but means that the check is ineffective for
> > these platforms.  To fix, replace the variable with macros.
> > 
> > Reported-by: Peter Maydell <address@hidden>
> > Signed-off-by: Michael S. Tsirkin <address@hidden>
> 
> Ugh.. I pulled this into my tree already (I've been having trouble
> with my test setup, which is why I haven't sent my own pullreq yet).
> However, it needs a s/%u/%llu/ to compile correctly on some platforms.

I need it to avoid breaking build. I fixed it up - want to drop it
from you tree? Or leave it there - git will resolve the trivial conflict.

> > ---
> >  hw/ppc/spapr.c | 14 ++++++++------
> >  1 file changed, 8 insertions(+), 6 deletions(-)
> > 
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index a642e66..b81f2ac 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -2630,8 +2630,8 @@ static void spapr_phb_placement(sPAPRMachineState 
> > *spapr, uint32_t index,
> >       * 1TiB 64-bit MMIO windows for each PHB.
> >       */
> >      const uint64_t base_buid = 0x800000020000000ULL;
> > -    const int max_phbs =
> > -        (SPAPR_PCI_LIMIT - SPAPR_PCI_BASE) / SPAPR_PCI_MEM64_WIN_SIZE - 1;
> > +#define SPAPR_MAX_PHBS ((SPAPR_PCI_LIMIT - SPAPR_PCI_BASE) / \
> > +                        SPAPR_PCI_MEM64_WIN_SIZE - 1)
> >      int i;
> >  
> >      /* Sanity check natural alignments */
> > @@ -2640,12 +2640,14 @@ static void spapr_phb_placement(sPAPRMachineState 
> > *spapr, uint32_t index,
> >      QEMU_BUILD_BUG_ON((SPAPR_PCI_MEM64_WIN_SIZE % 
> > SPAPR_PCI_MEM32_WIN_SIZE) != 0);
> >      QEMU_BUILD_BUG_ON((SPAPR_PCI_MEM32_WIN_SIZE % SPAPR_PCI_IO_WIN_SIZE) 
> > != 0);
> >      /* Sanity check bounds */
> > -    QEMU_BUILD_BUG_ON((max_phbs * SPAPR_PCI_IO_WIN_SIZE) > 
> > SPAPR_PCI_MEM32_WIN_SIZE);
> > -    QEMU_BUILD_BUG_ON((max_phbs * SPAPR_PCI_MEM32_WIN_SIZE) > 
> > SPAPR_PCI_MEM64_WIN_SIZE);
> > +    QEMU_BUILD_BUG_ON((SPAPR_MAX_PHBS * SPAPR_PCI_IO_WIN_SIZE) >
> > +                      SPAPR_PCI_MEM32_WIN_SIZE);
> > +    QEMU_BUILD_BUG_ON((SPAPR_MAX_PHBS * SPAPR_PCI_MEM32_WIN_SIZE) >
> > +                      SPAPR_PCI_MEM64_WIN_SIZE);
> >  
> > -    if (index >= max_phbs) {
> > +    if (index >= SPAPR_MAX_PHBS) {
> >          error_setg(errp, "\"index\" for PAPR PHB is too large (max %u)",
> > -                   max_phbs - 1);
> > +                   SPAPR_MAX_PHBS - 1);
> >          return;
> >      }
> >  
> 
> -- 
> David Gibson                  | I'll have my music baroque, and my code
> david AT gibson.dropbear.id.au        | minimalist, thank you.  NOT _the_ 
> _other_
>                               | _way_ _around_!
> http://www.ozlabs.org/~dgibson