[PATCH] x86/header: Use __DECLARE_FLEX_ARRAY() for struct setup_data flex array

[Federico Parola]

After the `data` member of struct setup_data was switched to a flex
array by commit 94dfc73e7cf4 ("treewide: uapi: Replace zero-length
arrays with flexible-array members"), the struct can no longer be used
as a header in a larger struct in C++, with errors like:
 flexible array member ‘setup_data::data’ not at end of ‘struct ...’
This breaks compilation of our userspace code which imports the header
in a C++ project.

Similar to commit 2619da73bb2f ("KVM: x86: Use __DECLARE_FLEX_ARRAY()
for UAPI structures with VLAs"), declare the member with
__DECLARE_FLEX_ARRAY(), which uses [0] for C++ compilation.

Fixes: 94dfc73e7cf4 ("treewide: uapi: Replace zero-length arrays with flexible-array members")
Signed-off-by: Federico Parola <fparola@xxxxxxxxx>
---
 arch/x86/include/uapi/asm/setup_data.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/uapi/asm/setup_data.h b/arch/x86/include/uapi/asm/setup_data.h
index 2671c4e1b3a0b..afe1e3a2a6564 100644
--- a/arch/x86/include/uapi/asm/setup_data.h
+++ b/arch/x86/include/uapi/asm/setup_data.h
@@ -28,7 +28,7 @@ struct setup_data {
 	__u64 next;
 	__u32 type;
 	__u32 len;
-	__u8 data[];
+	__DECLARE_FLEX_ARRAY(__u8, data);
 };
 
 /* extensible setup indirect data node */
-- 
2.47.3