Re: [PATCH] acpi: avoid uninialized-variable warning

[Andy Shevchenko]

On Wed, Apr 29, 2020 at 1:03 AM Arnd Bergmann <arnd@xxxxxxxx> wrote:
>
> Older compilers like gcc-4.8 produce a bogus warning here
>
> In file included from include/linux/compiler_types.h:68:0,
>                  from <command-line>:0:
> drivers/acpi/property.c: In function 'acpi_data_prop_read':
> include/linux/compiler-gcc.h:75:45: error: 'obj' may be used uninitialized in this function [-Werror=maybe-uninitialized]
>  #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
>                                              ^
> drivers/acpi/property.c:934:27: note: 'obj' was declared here
>   const union acpi_object *obj;
>                            ^
>
> Ensure the output is always initialized even when returning an error
> to avoid the warning.
>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
>  drivers/acpi/property.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/property.c b/drivers/acpi/property.c
> index e601c4511a8b..3aa71daeb0b4 100644
> --- a/drivers/acpi/property.c
> +++ b/drivers/acpi/property.c
> @@ -587,8 +587,10 @@ static int acpi_data_get_property_array(const struct acpi_device_data *data,
>         int ret, i;
>
>         ret = acpi_data_get_property(data, name, ACPI_TYPE_PACKAGE, &prop);
> -       if (ret)
> +       if (ret && obj) {

It changes semantics and requires obj to be non-NULL.

Should be
if (ret) {
  if (obj)
    *obj = NULL;
  return ret;
}

> +               *obj = NULL;
>                 return ret;
> +       }
>
>         if (type != ACPI_TYPE_ANY) {
>                 /* Check that all elements are of correct type. */
> --
> 2.26.0
>


-- 
With Best Regards,
Andy Shevchenko