Re: [PATCH] exynos4210_gic: Suppress gcc9 format-truncation warnings

[Peter Maydell]

On Fri, 4 Oct 2019 at 04:10, David Gibson <address@hidden> wrote:
>
> exynos4210_gic_realize() prints the number of cpus into some temporary
> buffers, but it only allows 3 bytes space for it.  That's plenty - I'm
> pretty sure that existing machines will only ever set this value to 2
> (EXYNOS4210_NCPUS).  But the compiler can't really be expected to figure
> that out.
>
> Some[*] gcc9 versions therefore emit -Wformat-truncation warnings.  Fix
> that by allowing more space in the temporary buffers - these are on stack
> very briefly before being essentially strdup()ed inside the memory region
> code, so there's not much cost to doing so.
>
> [*] The bizarre thing here, is that I've long gotten these warnings
> compiling in a 32-bit x86 container as host - Fedora 30 with
> gcc-9.2.1-1.fc30.i686 - but it compiles just fine on my normal x86_64 host
> - Fedora 30 with and gcc-9.2.1-1.fc30.x86_64.
>
> Signed-off-by: David Gibson <address@hidden>
> ---
>  hw/intc/exynos4210_gic.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/hw/intc/exynos4210_gic.c b/hw/intc/exynos4210_gic.c
> index a1b699b6ba..2e5e47f9ec 100644
> --- a/hw/intc/exynos4210_gic.c
> +++ b/hw/intc/exynos4210_gic.c
> @@ -290,8 +290,8 @@ static void exynos4210_gic_realize(DeviceState *dev, 
> Error **errp)
>      SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
>      const char cpu_prefix[] = "exynos4210-gic-alias_cpu";
>      const char dist_prefix[] = "exynos4210-gic-alias_dist";
> -    char cpu_alias_name[sizeof(cpu_prefix) + 3];
> -    char dist_alias_name[sizeof(cpu_prefix) + 3];
> +    char cpu_alias_name[sizeof(cpu_prefix) + 10];
> +    char dist_alias_name[sizeof(cpu_prefix) + 10];
>      SysBusDevice *gicbusdev;
>      uint32_t i;

If we assert() that num_cpu is always <= EXYNOS4210_NCPUS
is that sufficient to clue gcc in that the buffer can't overflow?

thanks
-- PMM