From: Nathan Chancellor <nathan@kernel.org>
To: Vinicius Tinti <viniciustinti@gmail.com>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>,
Nathan Chancellor <natechancellor@gmail.com>,
Theodore Ts'o <tytso@mit.edu>,
Nick Desaulniers <ndesaulniers@google.com>,
linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
clang-built-linux@googlegroups.com
Subject: Re: [PATCH v2] ext4: Enable code path when DX_DEBUG is set
Date: Sun, 31 Jan 2021 17:48:20 -0700 [thread overview]
Message-ID: <20210201004820.GA26230@localhost> (raw)
In-Reply-To: <20210201003125.90257-1-viniciustinti@gmail.com>
On Mon, Feb 01, 2021 at 12:31:25AM +0000, Vinicius Tinti wrote:
> By enabling -Wunreachable-code-aggressive on Clang the following code
> paths are unreachable.
>
> This has been present since commit ac27a0ec112a ("[PATCH] ext4: initial
> copy of files from ext3") and fs/ext3 had it present at the beginning of
> git history. It has not been changed since.
>
> Clang warns:
>
> fs/ext4/namei.c:831:17: warning: code will never be executed
> [-Wunreachable-code]
> unsigned n = count - 1;
> ^~~~~
> fs/ext4/namei.c:830:7: note: silence by adding parentheses to mark code as
> explicitly dead
> if (0) { // linear search cross check
> ^
> /* DISABLES CODE */ ( )
>
> Signed-off-by: Vinicius Tinti <viniciustinti@gmail.com>
> ---
> fs/ext4/namei.c | 23 ++++++++++++-----------
> 1 file changed, 12 insertions(+), 11 deletions(-)
>
> diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> index cf652ba3e74d..46ae6a4e4be5 100644
> --- a/fs/ext4/namei.c
> +++ b/fs/ext4/namei.c
> @@ -827,20 +827,21 @@ dx_probe(struct ext4_filename *fname, struct inode *dir,
> p = m + 1;
> }
>
> - if (0) { // linear search cross check
> - unsigned n = count - 1;
> - at = entries;
> - while (n--)
> +#ifdef DX_DEBUG
> + // linear search cross check
> + unsigned n = count - 1;
You are going to introduce an instance of -Wdeclaration-after-statement
here.
fs/ext4/namei.c:834:12: warning: ISO C90 forbids mixing declarations and
code [-Wdeclaration-after-statement]
unsigned n = count - 1;
^
1 warning generated.
The quick hack would be changing the
if (0) {
to
#ifdef DX_DEBUG
if (1) {
but that seems kind of ugly.
Other options would be turning DX_DEBUG into a proper Kconfig symbol so
that IS_ENABLED could be used or maybe combine it into
CONFIG_EXT4_DEBUG.
Cheers,
Nathan
next prev parent reply other threads:[~2021-02-01 0:49 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-29 18:58 [PATCH] ext4: Remove unreachable code Vinicius Tinti
2021-01-30 1:35 ` Nathan Chancellor
2021-01-30 6:42 ` Andreas Dilger
2021-02-01 0:31 ` [PATCH v2] ext4: Enable code path when DX_DEBUG is set Vinicius Tinti
2021-02-01 0:48 ` Nathan Chancellor [this message]
2021-02-01 12:49 ` Christoph Hellwig
2021-02-01 16:15 ` Vinicius Tinti
2021-02-01 17:13 ` Theodore Ts'o
2021-02-01 18:41 ` Vinicius Tinti
2021-02-01 20:45 ` Andreas Dilger
2021-02-01 21:09 ` Theodore Ts'o
2021-02-01 21:16 ` Nick Desaulniers
2021-02-01 21:38 ` Theodore Ts'o
2021-02-01 21:41 ` Nick Desaulniers
2021-02-01 22:05 ` Vinicius Tinti
2021-02-01 22:48 ` Theodore Ts'o
2021-02-01 23:09 ` Nick Desaulniers
2021-02-02 8:05 ` Christoph Hellwig
2021-02-02 16:28 ` [PATCH v3] " Vinicius Tinti
2021-02-03 5:39 ` Theodore Ts'o
2021-02-03 9:51 ` Vinicius Tinti
2021-02-01 16:58 ` [PATCH v2] " Theodore Ts'o
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