On Fri, Jul 12, 2019 at 11:01:21AM +0200, Arnd Bergmann wrote:
> clang gets confused by an uninitialized variable in what looks
> to it like a never executed code path:
>
> arch/x86/kernel/acpi/boot.c:618:13: error: variable 'polarity' is uninitialized when used here [-Werror,-Wuninitialized]
> polarity = polarity ? ACPI_ACTIVE_LOW : ACPI_ACTIVE_HIGH;
> ^~~~~~~~
> arch/x86/kernel/acpi/boot.c:606:32: note: initialize the variable 'polarity' to silence this warning
> int rc, irq, trigger, polarity;
> ^
> = 0
> arch/x86/kernel/acpi/boot.c:617:12: error: variable 'trigger' is uninitialized when used here [-Werror,-Wuninitialized]
> trigger = trigger ? ACPI_LEVEL_SENSITIVE : ACPI_EDGE_SENSITIVE;
> ^~~~~~~
> arch/x86/kernel/acpi/boot.c:606:22: note: initialize the variable 'trigger' to silence this warning
> int rc, irq, trigger, polarity;
> ^
> = 0
>
> This is unfortunately a design decision in clang and won't be fixed.
>
> Changing the acpi_get_override_irq() macro to an inline function
> reliably avoids the issue.
In this particular case it looks fine (perhaps in the future -1 shall be
replaced with proper error code).
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
But in general it looks like clang obscures use of pretty well working macros.
>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
> include/linux/acpi.h | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index a95cce5e82e7..9426b9aaed86 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -324,7 +324,10 @@ struct irq_domain *acpi_irq_create_hierarchy(unsigned int flags,
> #ifdef CONFIG_X86_IO_APIC
> extern int acpi_get_override_irq(u32 gsi, int *trigger, int *polarity);
> #else
> -#define acpi_get_override_irq(gsi, trigger, polarity) (-1)
> +static inline int acpi_get_override_irq(u32 gsi, int *trigger, int *polarity)
> +{
> + return -1;
> +}
> #endif
> /*
> * This function undoes the effect of one call to acpi_register_gsi().
> --
> 2.20.0
>
--
With Best Regards,
Andy Shevchenko
