hyperv: Avoid a hundred -Wflex-array-member-at-end warnings

PATCH Superseded Gustavo A. R. Silva 1 participant 1 message Aug 29, 2025

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Hyper-V/Azure core and drivers Microsoft MANA RDMA driver

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Gustavo A. R. Silva

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2025-08-29 11:42 UTC #0 lore raw

PATCH 1/1 hyperv: Avoid a hundred -Wflex-array-member-at-end warnings

-Wflex-array-member-not-at-end was introduced in GCC-14, and we are getting ready to enable it, globally.

Use the new TRAILING_OVERLAP() helper to fix 159 of the following type of warnings:

159 ./include/linux/hyperv.h:711:38: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

This helper creates a union between a flexible-array member (FAM) and a set of members that would otherwise follow it. This overlays the trailing members onto the FAM while preserving the original memory layout.

Also, move struct vmbus_close_msg close_msg; at the end of struct vmbus_channel, as struct vmbus_channel_msginfo, ends in a flexible array member.

Signed-off-by Gustavo A. R. Silva <[email protected]>

---
 include/linux/hyperv.h | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

include/linux/hyperv.h +6 -4

index a59c5c3e95fb..efdd570669fa 100644
@@ -708,8 +708,9 @@ struct vmbus_channel_msginfo {
 };
 
 struct vmbus_close_msg {
-	struct vmbus_channel_msginfo info;
-	struct vmbus_channel_close_channel msg;
+	TRAILING_OVERLAP(struct vmbus_channel_msginfo, info, msg,
+		struct vmbus_channel_close_channel msg;
+	);
 };
 
 enum vmbus_device_type {

@@ -800,8 +801,6 @@ struct vmbus_channel {
 	struct hv_ring_buffer_info outbound;	/* send to parent */
 	struct hv_ring_buffer_info inbound;	/* receive from parent */
 
-	struct vmbus_close_msg close_msg;
-
 	/* Statistics */
 	u64	interrupts;	/* Host to Guest interrupts */
 	u64	sig_events;	/* Guest to Host events */

@@ -1008,6 +1007,9 @@ struct vmbus_channel {
 
 	/* boolean to control visibility of sysfs for ring buffer */
 	bool ring_sysfs_visible;
+
+	/* Must be last --ends in a flexible-array member. */
+	struct vmbus_close_msg close_msg;
 };
 
 #define lock_requestor(channel, flags)					\

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