[PATCH 2/3] xen/efi: fix unitialized use warning

[Stewart Hildebrand <stewart.hildebrand@xxxxxxx>]

When building the hypervisor for arm64 with -Og, we encounter a (false)
uninitialized use warning:

arch/arm/efi/boot.c: In function ‘efi_start’:
arch/arm/efi/boot.c:1468:9: error: ‘argc’ may be used uninitialized 
[-Werror=maybe-uninitialized]
 1468 |         efi_arch_handle_cmdline(argc ? *argv : NULL, options, name.s);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/arm/efi/boot.c:1263:21: note: ‘argc’ was declared here
 1263 |     unsigned int i, argc;
      |                     ^~~~
cc1: all warnings being treated as errors

Fix this by initializing argc. As a precaution, also initialize argv.

Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
---
See previous discussion here
https://lists.xenproject.org/archives/html/xen-devel/2022-10/msg00805.html
---
 xen/common/efi/boot.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
index b69c83e354ee..c5850c26af9f 100644
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -1344,6 +1344,15 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE 
*SystemTable)
         if ( !base_video )
             efi_console_set_mode();
     }
+    else
+    {
+        /*
+         * Some compilers may emit a false "uninitialized use" warning for 
argc,
+         * so initialize argc/argv here to avoid the warning.
+         */
+        argc = 0;
+        argv = NULL;
+    }
 
     PrintStr(L"Xen " XEN_VERSION_STRING XEN_EXTRAVERSION
             " (c/s " XEN_CHANGESET ") EFI loader\r\n");
-- 
2.40.0