Re: [PATCH 06/46] error: Avoid error_propagate() when error is not used here

[Eric Blake]

On 6/24/20 11:43 AM, Markus Armbruster wrote:
> When all we do with an Error we receive into a local variable is
> propagating to somewhere else, we can just as well receive it there
> right away.  Coccinelle script:

This seems to be a recurring cleanup (witness commit 06592d7e, c0e90679, 
6b62d961).  In fact, shouldn't you just update that script with your 
enhancements here, and then run it directly, instead of embedding your 
tweaks in the commit message?

>      @@
>      identifier fun, err, errp;
>      expression list args;
>      @@
>      -    fun(args, &err);
>      +    fun(args, errp);
>           ... when != err
>               when strict
>      -    error_propagate(errp, err);

What does the 'when strict' accomplish?  The existing coccinelle script 
uses 'when != errp', which may be enough to address...

> The first two rules are prone to fail with "error_propagate(...)
> ... reachable by inconsistent control-flow paths".  Script without
> them re-run where that happens.

...the control-flow failures you hit?

> Manually double-check @err is not used afterwards.  Dereferencing it
> would be use after free, but checking whether it's null would be
> legitimate.  One such change to qbus_realize() backed out.
>
> Suboptimal line breaks tweaked manually.
>
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> ---

>   22 files changed, 31 insertions(+), 73 deletions(-)

At any rate, it's small enough to ensure all the changes remaining are 
still valid.

Reviewed-by: Eric Blake <eblake@redhat.com>

--
Eric Blake, Principal Software Engineer
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