Re: 4.9.0-rcX can not be built for ARM64

From: Julien Grall <julien.grall@arm.com>
To: Andrii Anisov <andrii_anisov@epam.com>,
	Xen Devel <xen-devel@lists.xen.org>
Cc: Wei Liu <wei.liu2@citrix.com>,
	nd@arm.com, Ian Jackson <ian.jackson@eu.citrix.com>
Subject: Re: 4.9.0-rcX can not be built for ARM64
Date: Mon, 15 May 2017 09:12:55 +0100	[thread overview]
Message-ID: <3549b528-1b1e-b2aa-bad2-ffad6cb43629@arm.com> (raw)
In-Reply-To: <6f7fd7ed-867b-8a9b-60ba-5087001df9cf@epam.com>



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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