Re: [Xen-devel] 4.9.0-rcX can not be built for ARM64

[Julien Grall <julien.grall@xxxxxxx>]

On 13/05/2017 13:38, Andrii Anisov wrote:
> Dear All,
Hi Andrii,

> During the XEN 4.9.0-rc4 testing on Renesas R-Car Gen3 platform I faced
> a bug at compilation step.
Thank you for testing Xen on your board.

> Again, the libxl_arm_acpi.c can not be built:
>
>
> | In file included from libxl_arm.h:17:0,
> |                  from libxl_arm_acpi.c:19:
> | libxl_arm_acpi.c: In function 'libxl__get_acpi_size':
> | libxl_internal.h:129:44: error: 'size' may be used uninitialized in
> this function [-Werror=maybe-uninitialized]
> |      (((unsigned long)(_val)+(1UL<<(_order))-1) & ~((1UL<<(_order))-1))
> |                                             ^
> | libxl_arm_acpi.c:101:14: note: 'size' was declared here
> |      uint64_t size;
> |               ^
> | libxl_arm_acpi.c: In function 'libxl__prepare_acpi':
> | libxl_arm_acpi.c:152:33: error: 'size' may be used uninitialized in
> this function [-Werror=maybe-uninitialized]
> |      dom->acpi_modules[0].length += ROUNDUP(acpitables[MADT].size, 3);
> |                                  ^
> | libxl_arm_acpi.c:126:12: note: 'size' was declared here
> |      size_t size;
> |             ^
It looks like you compiler does not (validly?) detect that size will 
always be initialized when (rc > 0). Can you try this small patch below:
diff --git a/tools/libxl/libxl_arm_acpi.c b/tools/libxl/libxl_arm_acpi.c
index db113dbf85..f61aec672b 100644
--- a/tools/libxl/libxl_arm_acpi.c
+++ b/tools/libxl/libxl_arm_acpi.c
@@ -73,6 +73,8 @@ static int libxl__estimate_madt_size(libxl__gc *gc,
 {
     int rc = 0;

+    *size = 0;
+
     switch (info->arch_arm.gic_version) {
     case LIBXL_GIC_VERSION_V2:
         *size = sizeof(struct acpi_table_madt) +

Cheers,

--
Julien Grall

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