From c3bc36d4d0b957bbb1ce8e71f6ff8c8ea54000bb Mon Sep 17 00:00:00 2001
From: Auke Kok <auke.kok@versity.com>
Date: Mon, 21 Apr 2025 23:04:18 -0400
Subject: [PATCH] Fix compiler warnings for flex array definitions.

Instead of defining a struct that ends with a flex array member with
`val[0]`, the compiler now balks at this since technically, the spec
considers this unsanitary. As a result however, we can't memcpy to
`struct->val` since that's a pointer and now we're writing something of
a different length (u8's in our case) into something that's of pointer
size. So there we have to do the opposite, and memcpy to
&struct->val[0].

Signed-off-by: Auke Kok <auke.kok@versity.com>
---
 kmod/src/btree.c | 4 ++--
 kmod/src/btree.h | 2 +-
 kmod/src/item.c  | 8 ++++----
 kmod/src/wkic.c  | 4 ++--
 4 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/kmod/src/btree.c b/kmod/src/btree.c
index 7a21afc7..c6baa3be 100644
--- a/kmod/src/btree.c
+++ b/kmod/src/btree.c
@@ -2042,7 +2042,7 @@ struct merged_item {
 	u64 seq;
 	u8 flags;
 	unsigned int val_len;
-	u8 val[0];
+	u8 val[];
 };
 
 static inline struct merged_item *mitem_container(struct rb_node *node)
@@ -2208,7 +2208,7 @@ static int merge_read_item(struct super_block *sb, struct scoutfs_key *key, u64
 	mitem->flags = flags;
 	mitem->val_len = val_len;
 	if (val_len)
-		memcpy(mitem->val, val, val_len);
+		memcpy(&mitem->val[0], val, val_len);
 
 	if (found) {
 		replace_mitem(rng, found, mitem);
diff --git a/kmod/src/btree.h b/kmod/src/btree.h
index 8656dd65..065c190e 100644
--- a/kmod/src/btree.h
+++ b/kmod/src/btree.h
@@ -30,7 +30,7 @@ struct scoutfs_btree_item_list {
 	u64 seq;
 	u8 flags;
 	int val_len;
-	u8 val[0];
+	u8 val[];
 };
 
 int scoutfs_btree_lookup(struct super_block *sb,
diff --git a/kmod/src/item.c b/kmod/src/item.c
index 44357e6d..330f3f78 100644
--- a/kmod/src/item.c
+++ b/kmod/src/item.c
@@ -148,7 +148,7 @@ struct cached_item {
 	unsigned int val_len;
 	struct scoutfs_key key;
 	u64 seq;
-	char val[0];
+	char val[];
 };
 
 #define CACHED_ITEM_ALIGN 8
@@ -426,7 +426,7 @@ static struct cached_item *alloc_item(struct cached_page *pg,
 	item->seq = seq;
 
 	if (val_len)
-		memcpy(item->val, val, val_len);
+		memcpy(&item->val[0], val, val_len);
 
 	update_pg_max_seq(pg, item);
 
@@ -2053,7 +2053,7 @@ int scoutfs_item_update(struct super_block *sb, struct scoutfs_key *key,
 
 	if (val_len <= found->val_len) {
 		if (val_len)
-			memcpy(found->val, val, val_len);
+			memcpy(&found->val[0], val, val_len);
 		if (val_len < found->val_len)
 			pg->erased_bytes += item_val_bytes(found->val_len) -
 					    item_val_bytes(val_len);
@@ -2370,7 +2370,7 @@ int scoutfs_item_write_dirty(struct super_block *sb)
 			lst->seq = item->seq;
 			lst->flags = item->deletion ? SCOUTFS_ITEM_FLAG_DELETION : 0;
 			lst->val_len = item->val_len;
-			memcpy(lst->val, item->val, item->val_len);
+			memcpy(&lst->val[0], item->val, item->val_len);
 		}
 
 		spin_lock(&cinf->dirty_lock);
diff --git a/kmod/src/wkic.c b/kmod/src/wkic.c
index 44eef494..0dc476f4 100644
--- a/kmod/src/wkic.c
+++ b/kmod/src/wkic.c
@@ -171,7 +171,7 @@ struct wkic_item {
 	u64 seq;
 	unsigned int val_len;
 	u8 flags;
-	u8 val[0] __aligned(ARCH_KMALLOC_MINALIGN); /* totls have native structs */
+	u8 val[] __aligned(ARCH_KMALLOC_MINALIGN); /* totls have native structs */
 };
 
 static struct wkic_item *witem_container(struct rb_node *node)
@@ -763,7 +763,7 @@ static void fill_page_items(struct super_block *sb, struct wkic_page *wpage, str
 		pg_item->val_len = witem->val_len;
 		pg_item->flags = witem->flags;
 		if (witem->val_len)
-			memcpy(pg_item->val, witem->val, witem->val_len);
+			memcpy(&pg_item->val[0], witem->val, witem->val_len);
 
 		/* always inserting greatest item into page */
 		rb_link_node(&pg_item->node, parent, node);