Re: [PATCH] hw/openrisc/openrisc_sim: Add assertion to silent GCC warning

[Thomas Huth]

On 08/06/2020 09.14, Philippe Mathieu-Daudé wrote:
> When compiling with GCC 10 (Fedora 32) using CFLAGS=-O2 we get:
> 
>     CC      or1k-softmmu/hw/openrisc/openrisc_sim.o
>   hw/openrisc/openrisc_sim.c: In function ‘openrisc_sim_init’:
>   hw/openrisc/openrisc_sim.c:87:42: error: ‘cpu_irqs[0]’ may be used 
> uninitialized in this function [-Werror=maybe-uninitialized]
>      87 |         sysbus_connect_irq(s, i, cpu_irqs[i][irq_pin]);
>         |                                  ~~~~~~~~^~~
> 
> While humans can tell smp_cpus will always be in the [1, 2] range,
> (openrisc_sim_machine_init sets mc->max_cpus = 2), the compiler
> can't.
> 
> Add an assertion to give the compiler a hint there's no use of
> uninitialized data.
> 
> Buglink: https://bugs.launchpad.net/qemu/+bug/1874073
> Reported-by: Martin Liška <mliska@suse.cz>
> Suggested-by: Peter Maydell <peter.maydell@linaro.org>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  hw/openrisc/openrisc_sim.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/hw/openrisc/openrisc_sim.c b/hw/openrisc/openrisc_sim.c
> index d08ce61811..02f5259e5e 100644
> --- a/hw/openrisc/openrisc_sim.c
> +++ b/hw/openrisc/openrisc_sim.c
> @@ -134,6 +134,7 @@ static void openrisc_sim_init(MachineState *machine)
>      int n;
>      unsigned int smp_cpus = machine->smp.cpus;
>  
> +    assert(smp_cpus >= 1 && smp_cpus <= 2);
>      for (n = 0; n < smp_cpus; n++) {
>          cpu = OPENRISC_CPU(cpu_create(machine->cpu_type));
>          if (cpu == NULL) {
> 

Reviewed-by: Thomas Huth <thuth@redhat.com>