linux-kernel - Re: [PATCH] ACPI/IORT: Fix GCC 12 warning

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Message-ID: <fcb52c7b-a222-126e-fb3c-d57011506cf8@arm.com>
Date:   Thu, 10 Feb 2022 18:06:24 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Victor Erminpour <victor.erminpour@...cle.com>,
        lorenzo.pieralisi@....com
Cc:     guohanjun@...wei.com, sudeep.holla@....com, rafael@...nel.org,
        lenb@...nel.org, linux-acpi@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        trivial@...nel.org
Subject: Re: [PATCH] ACPI/IORT: Fix GCC 12 warning

On 2022-02-10 00:32, Victor Erminpour wrote:
> When building with automatic stack variable initialization, GCC 12
> complains about variables defined outside of switch case statements.
> Move the variable into the case that uses it, which silences the warning:
> 
> ./drivers/acpi/arm64/iort.c:1670:59: error: statement will never be executed [-Werror=switch-unreachable]
>    1670 |                         struct acpi_iort_named_component *ncomp;
>         |                                                           ^~~~~

Notwithstanding the fact that that warning is nonsensical, this patch 
changes valid C code into invalid C code that doesn't even compile:

drivers/acpi/arm64/iort.c: In function ‘acpi_iort_dma_get_max_cpu_address’:
drivers/acpi/arm64/iort.c:1669:4: error: a label can only be part of a 
statement and a declaration is not a statement
  1669 |    struct acpi_iort_named_component *ncomp;
       |    ^~~~~~
drivers/acpi/arm64/iort.c:1676:4: error: a label can only be part of a 
statement and a declaration is not a statement
  1676 |    struct acpi_iort_root_complex *rc;
       |    ^~~~~~

Robin.

> Signed-off-by: Victor Erminpour <victor.erminpour@...cle.com>
> ---
>   drivers/acpi/arm64/iort.c | 8 +++-----
>   1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> index 3b23fb775ac4..5c5d2e56d756 100644
> --- a/drivers/acpi/arm64/iort.c
> +++ b/drivers/acpi/arm64/iort.c
> @@ -1645,7 +1645,7 @@ void __init acpi_iort_init(void)
>    */
>   phys_addr_t __init acpi_iort_dma_get_max_cpu_address(void)
>   {
> -	phys_addr_t limit = PHYS_ADDR_MAX;
> +	phys_addr_t local_limit, limit = PHYS_ADDR_MAX;
>   	struct acpi_iort_node *node, *end;
>   	struct acpi_table_iort *iort;
>   	acpi_status status;
> @@ -1667,17 +1667,15 @@ phys_addr_t __init acpi_iort_dma_get_max_cpu_address(void)
>   			break;
>   
>   		switch (node->type) {
> -			struct acpi_iort_named_component *ncomp;
> -			struct acpi_iort_root_complex *rc;
> -			phys_addr_t local_limit;
> -
>   		case ACPI_IORT_NODE_NAMED_COMPONENT:
> +			struct acpi_iort_named_component *ncomp;
>   			ncomp = (struct acpi_iort_named_component *)node->node_data;
>   			local_limit = DMA_BIT_MASK(ncomp->memory_address_limit);
>   			limit = min_not_zero(limit, local_limit);
>   			break;
>   
>   		case ACPI_IORT_NODE_PCI_ROOT_COMPLEX:
> +			struct acpi_iort_root_complex *rc;
>   			if (node->revision < 1)
>   				break;
>   
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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