On 2/10/22 10:06 AM, Robin Murphy wrote:

On 2022-02-10 00:32, Victor Erminpour wrote:

quoted

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.

Hi Robin,

Thank you for your constructive criticism.
Could the solution be enclosing the case statement in curly braces?

I know this isn't a big issue for you, but this is a legitimate error 
for people
building the kernel with GCC 12 and CONFIG_INIT_STACK_ALL_ZERO enabled.

Regards,
--Victor

quoted

Signed-off-by: Victor Erminpour <redacted>
---
  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;

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