[v3,05/25] scripts: add coccinelle script to fix error_append_hint usage

error_append_hint will not work, if errp == &fatal_error, as program
will exit before error_append_hint call. Fix this by use of special
macro ERRP_FUNCTION_BEGIN.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---

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 .../fix-error_append_hint-usage.cocci         | 25 +++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 scripts/coccinelle/fix-error_append_hint-usage.cocci

On 9/24/19 3:08 PM, Vladimir Sementsov-Ogievskiy wrote:
> error_append_hint will not work, if errp == &fatal_error, as program
> will exit before error_append_hint call. Fix this by use of special
> macro ERRP_FUNCTION_BEGIN.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---

With the approach of a partial cleanup (rather than globally enforcing
it for all functions with errp parameter), we'll probably be rerunning
this Coccinelle script regularly, to track down any regressions.


> +++ b/scripts/coccinelle/fix-error_append_hint-usage.cocci
> @@ -0,0 +1,25 @@
> +@rule0@
> +// Add invocation to errp-functions
> +identifier fn;
> +@@
> +
> + fn(..., Error **errp, ...)
> + {
> ++   ERRP_FUNCTION_BEGIN();
> +    <+...
> +    error_append_hint(errp, ...);
> +    ...+>
> + }

Does not catch the case that we want to also use the macro for any use
of *errp, but we can augment that later.

> +
> +@@
> +// Drop doubled invocation
> +identifier rule0.fn;
> +@@
> +
> + fn(...)
> +{
> +    ERRP_FUNCTION_BEGIN();
> +-   ERRP_FUNCTION_BEGIN();
> +    ...
> +}

This is smaller than the script you posted in v2, and thus I'm a bit
more confident in stating that it looks correct and idempotent.

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

On 9/24/19 3:08 PM, Vladimir Sementsov-Ogievskiy wrote:
> error_append_hint will not work, if errp == &fatal_error, as program
> will exit before error_append_hint call. Fix this by use of special
> macro ERRP_FUNCTION_BEGIN.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---

>  .../fix-error_append_hint-usage.cocci         | 25 +++++++++++++++++++
>  1 file changed, 25 insertions(+)
>  create mode 100644 scripts/coccinelle/fix-error_append_hint-usage.cocci
> 

> +}
> +
> 

Why are you creating a file with a trailing blank line?

24.09.2019 23:48, Eric Blake wrote:
> On 9/24/19 3:08 PM, Vladimir Sementsov-Ogievskiy wrote:
>> error_append_hint will not work, if errp == &fatal_error, as program
>> will exit before error_append_hint call. Fix this by use of special
>> macro ERRP_FUNCTION_BEGIN.
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> ---
> 
> With the approach of a partial cleanup (rather than globally enforcing
> it for all functions with errp parameter), we'll probably be rerunning
> this Coccinelle script regularly, to track down any regressions.
> 
> 
>> +++ b/scripts/coccinelle/fix-error_append_hint-usage.cocci
>> @@ -0,0 +1,25 @@
>> +@rule0@
>> +// Add invocation to errp-functions
>> +identifier fn;
>> +@@
>> +
>> + fn(..., Error **errp, ...)
>> + {
>> ++   ERRP_FUNCTION_BEGIN();
>> +    <+...
>> +    error_append_hint(errp, ...);
>> +    ...+>
>> + }
> 
> Does not catch the case that we want to also use the macro for any use
> of *errp, but we can augment that later.

I don't want to include *errp here, as actually a lot of *errp invocations in
code are correct: they do it if errp is not NULL. So, it's not related to plan B.

Still, I think we forget about error_prepend :)))

I've checked, if I include error_prepend here, series becomes 30 patches, which is
not significantly larger. So I think, I'll cover error_prepend in v4.

> 
>> +
>> +@@
>> +// Drop doubled invocation
>> +identifier rule0.fn;
>> +@@
>> +
>> + fn(...)
>> +{
>> +    ERRP_FUNCTION_BEGIN();
>> +-   ERRP_FUNCTION_BEGIN();
>> +    ...
>> +}
> 
> This is smaller than the script you posted in v2, and thus I'm a bit
> more confident in stating that it looks correct and idempotent.
> 
> Reviewed-by: Eric Blake <eblake@redhat.com>
>