Re: [PATCH-for-5.2] acpi-build: Fix maybe-uninitialized warning when ACPI hotplug is off

[Michael S. Tsirkin]

On Sat, Nov 07, 2020 at 08:38:51PM +0530, Ani Sinha wrote:
>  This fixes the following warning (gcc 9.3.0 on Ubuntu):
> 
>   ../hw/i386/acpi-build.c: In function 'build_append_pci_bus_devices':
>   ../hw/i386/acpi-build.c:496:9: error: 'method' may be used uninitialized
>   in this function [-Werror=maybe-uninitialized]
>     496 |         aml_append(parent_scope, method);
>         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   cc1: all warnings being treated as errors
> 
> Fixes: df4008c9c59 ("piix4: don't reserve hw resources when hotplug is off 
> globally")
> Reported-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> Signed-off-by: Ani Sinha <ani@anisinha.ca>
> ---
>  hw/i386/acpi-build.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index 4f66642d88..79b86d4a36 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -349,7 +349,7 @@ static void build_append_pcihp_notify_entry(Aml *method, 
> int slot)
>  static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus,
>                                           bool pcihp_bridge_en)
>  {
> -    Aml *dev, *notify_method = NULL, *method;
> +    Aml *dev, *notify_method = NULL, *method = NULL;
>      QObject *bsel;
>      PCIBus *sec;
>      int i;
> @@ -492,7 +492,7 @@ static void build_append_pci_bus_devices(Aml 
> *parent_scope, PCIBus *bus,
>          }
>      }
>  
> -    if (bsel || pcihp_bridge_en) {
> +    if (method) {
>          aml_append(parent_scope, method);
>      }
>      qobject_unref(bsel);

I prefer Philippe's fix I think - gcc does not warn about it but
using method when it's NULL would lead to a crash.

> -- 
> 2.25.1