Re: [PATCH-for-5.1 v3 3/7] scripts/coccinelle: Find eventually missing error_propagate() calls

[Markus Armbruster]

Philippe Mathieu-Daudé <address@hidden> writes:

> In some places in we put an error into a local Error*, but
> forget to use it. Add a Coccinelle patch to find such cases
> and report them.
>
> Inspired-by: Peter Maydell <address@hidden>
> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> ---
>  .../find-missing-error_propagate.cocci        | 53 +++++++++++++++++++
>  MAINTAINERS                                   |  1 +
>  2 files changed, 54 insertions(+)
>  create mode 100644 scripts/coccinelle/find-missing-error_propagate.cocci
>
> diff --git a/scripts/coccinelle/find-missing-error_propagate.cocci 
> b/scripts/coccinelle/find-missing-error_propagate.cocci
> new file mode 100644
> index 0000000000..8b75b37b64
> --- /dev/null
> +++ b/scripts/coccinelle/find-missing-error_propagate.cocci
> @@ -0,0 +1,53 @@
> +// Find places likely missing error-propagation code, but code is too
> +// complex for automatic transformation, so manual analysis is required.
> +//
> +// Copyright: (C) 2020 Philippe Mathieu-Daudé
> +// This work is licensed under the terms of the GNU GPLv2 or later.
> +//
> +// spatch \
> +//  --macro-file scripts/cocci-macro-file.h --include-headers \
> +//  --sp-file scripts/coccinelle/find-missing-error_propagate.cocci
> +//
> +// Inspired by https://www.mail-archive.com/address@hidden/msg691638.html
> +
> +
> +// First match two subsequent calls using local Error*
> +// in function provided a Error** argument
> +//
> +@discard_func_with_errp_argument@
> +typedef Error;
> +Error *local_err;
> +identifier func, errp, errfunc1, errfunc2;
> +@@
> +void func(..., Error **errp)
> +{
> + <+...
> + errfunc1(..., &local_err);
> + ... when != local_err          // local_err is not used between the calls
> + errfunc2(..., &local_err);
> + ...+>
> +}
> +
> +
> +// Again, match two subsequent calls using local Error*
> +// but ignoring within functions provided a Error** argument
> +//
> +@manual depends on never discard_func_with_errp_argument@
> +Error *local_err;
> +identifier errfunc1, errfunc2;
> +position p;
> +@@
> + errfunc1@p(..., &local_err);
> + ... when != local_err
> + errfunc2(..., &local_err);
> +
> +
> +// As it is likely too complex to transform, report the hit
> +//
> +@script:python@
> +f << manual.errfunc1;
> +p << manual.p;
> +@@
> +print("[[manual check required: "
> +      "error_propagate() might be missing in {}() {}:{}:{}]]".format(
> +            f, p[0].file, p[0].line, p[0].column))

You report matches of the second rule only, i.e. only within functions
that doin't take an Error ** argument.  Why not everywhere?

> diff --git a/MAINTAINERS b/MAINTAINERS
> index 77b93612bc..1150ec95a8 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -2058,6 +2058,7 @@ F: scripts/coccinelle/add-missing-error_propagate.cocci
>  F: scripts/coccinelle/err-bad-newline.cocci
>  F: scripts/coccinelle/error-use-after-free.cocci
>  F: scripts/coccinelle/error_propagate_null.cocci
> +F: scripts/coccinelle/find-missing-error_propagate.cocci
>  F: scripts/coccinelle/remove_local_err.cocci
>  F: scripts/coccinelle/simplify-init-realize-error_propagate.cocci
>  F: scripts/coccinelle/use-error_abort-in-instance_init.cocci