linux-kernel - Re: [PATCH v3] coccinelle: misc: add uninitialized

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Date:   Tue, 1 Sep 2020 12:08:43 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...ia.fr>
To:     Denis Efremov <efremov@...ux.com>
cc:     cocci@...teme.lip6.fr, linux-kernel@...r.kernel.org,
        Kees Cook <keescook@...omium.org>,
        "Gustavo A . R . Silva" <gustavoars@...nel.org>
Subject: Re: [PATCH v3] coccinelle: misc: add uninitialized_var.cocci
 script



On Tue, 1 Sep 2020, Denis Efremov wrote:

> uninitialized_var() macro was removed from the sources [1] and
> other warning-silencing tricks were deprecated [2]. The purpose of this
> cocci script is to prevent new occurrences of uninitialized_var()
> open-coded variants.
>
> [1] commit 63a0895d960a ("compiler: Remove uninitialized_var() macro")
> [2] commit 4b19bec97c88 ("docs: deprecated.rst: Add uninitialized_var()")

Thanks!  I find that much more understandable.

julia

>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Gustavo A. R. Silva <gustavoars@...nel.org>
> Signed-off-by: Denis Efremov <efremov@...ux.com>
> ---
> Changes in v2:
>  - Documentation cited in the script's description
>  - kernel.org link added to the diagnostics messages
>  - "T *var = &var;" pattern removed
>  - "var =@p var", "var =@p *(&(var))" patterns added
> Changes in v3:
>  - commit's description changed
>
>  .../coccinelle/misc/uninitialized_var.cocci   | 51 +++++++++++++++++++
>  1 file changed, 51 insertions(+)
>  create mode 100644 scripts/coccinelle/misc/uninitialized_var.cocci
>
> diff --git a/scripts/coccinelle/misc/uninitialized_var.cocci b/scripts/coccinelle/misc/uninitialized_var.cocci
> new file mode 100644
> index 000000000000..8fa845cefe11
> --- /dev/null
> +++ b/scripts/coccinelle/misc/uninitialized_var.cocci
> @@ -0,0 +1,51 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +///
> +/// Please, don't reintroduce uninitialized_var().
> +/// From Documentation/process/deprecated.rst:
> +///  For any compiler warnings about uninitialized variables, just add
> +///  an initializer. Using warning-silencing tricks is dangerous as it
> +///  papers over real bugs (or can in the future), and suppresses unrelated
> +///  compiler warnings (e.g. "unused variable"). If the compiler thinks it
> +///  is uninitialized, either simply initialize the variable or make compiler
> +///  changes. Keep in mind that in most cases, if an initialization is
> +///  obviously redundant, the compiler's dead-store elimination pass will make
> +///  sure there are no needless variable writes.
> +///
> +// Confidence: High
> +// Copyright: (C) 2020 Denis Efremov ISPRAS
> +// Options: --no-includes --include-headers
> +//
> +
> +virtual context
> +virtual report
> +virtual org
> +
> +@r@
> +identifier var;
> +type T;
> +position p;
> +@@
> +
> +(
> +* T var =@p var;
> +|
> +* T var =@p *(&(var));
> +|
> +* var =@p var
> +|
> +* var =@p *(&(var))
> +)
> +
> +@...ipt:python depends on report@
> +p << r.p;
> +@@
> +
> +coccilib.report.print_report(p[0],
> +  "WARNING this kind of initialization is deprecated (https://www.kernel.org/doc/html/latest/process/deprecated.html#uninitialized-var)")
> +
> +@...ipt:python depends on org@
> +p << r.p;
> +@@
> +
> +coccilib.org.print_todo(p[0],
> +  "WARNING this kind of initialization is deprecated (https://www.kernel.org/doc/html/latest/process/deprecated.html#uninitialized-var)")
> --
> 2.26.2
>
>