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

[David Gibson]

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.

> ---
>  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

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