linux-kernel - [PATCH 5.2 003/215] btrfs: shut up bogus -Wmaybe-uninitialized warning

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Message-Id: <20190729190740.374967721@linuxfoundation.org>
Date:   Mon, 29 Jul 2019 21:19:59 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        David Sterba <dsterba@...e.com>
Subject: [PATCH 5.2 003/215] btrfs: shut up bogus -Wmaybe-uninitialized warning

From: Arnd Bergmann <arnd@...db.de>

commit 6c64460cdc8be5fa074aa8fe2ae8736d5792bdc5 upstream.

gcc sometimes can't determine whether a variable has been initialized
when both the initialization and the use are conditional:

fs/btrfs/props.c: In function 'inherit_props':
fs/btrfs/props.c:389:4: error: 'num_bytes' may be used uninitialized in this function [-Werror=maybe-uninitialized]
    btrfs_block_rsv_release(fs_info, trans->block_rsv,

This code is fine. Unfortunately, I cannot think of a good way to
rephrase it in a way that makes gcc understand this, so I add a bogus
initialization the way one should not.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
Reviewed-by: David Sterba <dsterba@...e.com>
[ gcc 8 and 9 don't emit the warning ]
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/btrfs/props.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/btrfs/props.c
+++ b/fs/btrfs/props.c
@@ -337,7 +337,7 @@ static int inherit_props(struct btrfs_tr
 	for (i = 0; i < ARRAY_SIZE(prop_handlers); i++) {
 		const struct prop_handler *h = &prop_handlers[i];
 		const char *value;
-		u64 num_bytes;
+		u64 num_bytes = 0;
 
 		if (!h->inheritable)
 			continue;