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From: Markus Armbruster <armbru@redhat.com>
To: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
	Michael Roth <mdroth@linux.vnet.ibm.com>,
	"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
	Gerd Hoffmann <kraxel@redhat.com>
Subject: Re: [PATCH v4 01/31] errp: rename errp to errp_in where it is IN-argument
Date: Wed, 09 Oct 2019 20:48:42 +0200	[thread overview]
Message-ID: <87imoxzred.fsf@dusky.pond.sub.org> (raw)
In-Reply-To: 155beb1a-b50f-4ee0-ec19-4a71f620de79@virtuozzo.com

Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> writes:

> 08.10.2019 15:05, Markus Armbruster wrote:
>> Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> writes:
>> 
>>> 08.10.2019 12:08, Markus Armbruster wrote:
>>>> Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> writes:
>>>>
>>>>> Error **errp is almost always OUT-argument: it's assumed to be NULL, or
>>>>> pointer to NULL-initialized pointer, or pointer to error_abort or
>>>>> error_fatal, for callee to report error.
>>>>
>>>> Yes.
>>>>
>>>>> But very few functions instead get Error **errp as IN-argument:
>>>>> it's assumed to be set, and callee should clean it.
>>>>
>>>> What do you mean by "callee should clean"?  Let's see below.
>>>>
>>>>> In such cases, rename errp to errp_in.
>>>>
>>>> I acknowledge that errp arguments that don't have the usual meaning can
>>>> be confusing.
>>>>
>>>> Naming can help, comments can help, but perhaps we can tweak the code to
>>>> avoid the problem instead.  Let's see:
>>>>
>>>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>>>>> Reviewed-by: Eric Blake <eblake@redhat.com>
>> [...]
>>>> We can avoid the confusing Error **errp in all three cases by peeling
>>>> off an indirection.  What do you think?
>>>>
>>>
>>> I like the idea, thanks! I think, I'll try to make a patch.
>>>
>>> But you are right, unfortunately there more cases, at least, pointed by
>>> Greg
>>>
>>> error_append_socket_sockfd_hint and
>>> error_append_security_model_hint
>>>
>>> Which don't free error..
>> 
>> Neither do error_append_hint() and error_prepend().
>> 
>> For anything named error_append_FOO_hint() or error_prepend_FOO(),
>> confusion seems unlikely.
>> 
>>>                           But if they append hint, they should always be called
>>> on wrapped errp, accordingly to the problem about fatal_error, so they may
>>> be converted to Error *err too.. Hmm, I should think about the script to find
>>> such functions.
>> 
>> I figure I better read more of your series before I comment on this
>> thought.
>> 
>
> Me trying to find more such functions:
>
> script:
> # cat ../up-fix-error_append_hint/find.py
> #!/usr/bin/env python
> import re
> import sys
>
> ret_type = r'^[^{};#]+( |\*|\*\*)'
> name = r'(?P<name>\w+)'
> args = r'\([^{};#]*Error \*\*errp[^{};#]*\)'
> body_before_errp = r'((?<!errp)[^}]|(?<!^)})*'
>
> caller = '(if ?|assert|' \
>            'error_(v?prepend|get_pretty|append_hint|free|free_or_abort)|' \
>            '(warn|error)_reportf?_err)'
>
> # Match 'caller(errp', 'caller(*errp', 'errp ?'
> access_errp = '(' + caller + r'\(\*?errp|errp \?)'
>
> r = re.compile(ret_type + name + args + '\s*^\{' + body_before_errp + access_errp, re.M)
>
> with open(sys.argv[1]) as f:
>      text = f.read()
>
> for m in r.finditer(text):
>      print(m.groupdict()['name'])
>
>
> search:
> # git ls-files | grep '\.\(h\|c\)$' | while read f; do ../up-fix-error_append_hint/find.py $f; done
> vmdk_co_create_opts_cb

Forwards errp to vmdk_create_extent().

Also asserts errp == NULL, which looks suspicious.  Not your problem.

> error_append_security_model_hint
> error_append_socket_sockfd_hint

Convenience functions to append a canned hint with error_append_hint().
Their name makes confusion unlikely.

> qemu_file_get_error_obj

Returns an error object in an unusual way: error_copy() instead of
error_setg().

Suspicious-looking qemu_file_set_error_obj() nearby: it either stores
@err in @f, or reports it to stderr / current monitor.  Not your
problem.

> hmp_handle_error

Covered by your patch, already discussed.

> qbus_list_bus
> qbus_list_dev

Convenience functions to append hints with error_append_hint().
Function names do not hint at that (pardon the pun).

> kvmppc_hint_smt_possible

Convenience function to append hints with error_append_hint().  Function
name hints weakly.

> vnc_client_io_error

Covered by your patch, already discussed.

> error_handle_fatal
> error_setv
> error_prepend
> error_setg_win32_internal
> error_free_or_abort

Let's not worry about error.c itself.

> vmdk_co_create_opts_cb and qemu_file_get_error_obj are false positives I think

Agree.


  reply	other threads:[~2019-10-09 20:08 UTC|newest]

Thread overview: 81+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-01 15:52 [PATCH v4 00/31] error: auto propagated local_err Vladimir Sementsov-Ogievskiy
2019-10-01 15:52 ` [PATCH v4 01/31] errp: rename errp to errp_in where it is IN-argument Vladimir Sementsov-Ogievskiy
2019-10-08  9:08   ` Markus Armbruster
2019-10-08  9:30     ` Vladimir Sementsov-Ogievskiy
2019-10-08 12:05       ` Markus Armbruster
2019-10-09 10:08         ` Vladimir Sementsov-Ogievskiy
2019-10-09 18:48           ` Markus Armbruster [this message]
2019-10-09  9:42     ` Vladimir Sementsov-Ogievskiy
2019-10-09 18:51       ` Markus Armbruster
2019-10-01 15:52 ` [PATCH v4 02/31] hw/core/loader-fit: fix freeing errp in fit_load_fdt Vladimir Sementsov-Ogievskiy
2019-10-01 16:13   ` Eric Blake
2019-10-08 14:24   ` Markus Armbruster
2019-10-01 15:52 ` [PATCH v4 03/31] net/net: fix local variable shadowing in net_client_init Vladimir Sementsov-Ogievskiy
2019-10-08 14:34   ` Markus Armbruster
2019-10-01 15:52 ` [PATCH v4 04/31] error: auto propagated local_err Vladimir Sementsov-Ogievskiy
2019-10-01 16:17   ` Eric Blake
2019-10-02 10:15   ` Roman Kagan
2019-10-02 14:00     ` Eric Blake
2019-10-08 16:03   ` Markus Armbruster
2019-10-08 16:19     ` Greg Kurz
2019-10-08 18:24       ` Markus Armbruster
2019-10-09  8:04   ` Markus Armbruster
2019-10-09  8:17     ` Vladimir Sementsov-Ogievskiy
2019-10-09 19:09       ` Markus Armbruster
2019-10-01 15:52 ` [PATCH v4 05/31] scripts: add script to fix error_append_hint/error_prepend usage Vladimir Sementsov-Ogievskiy
2019-10-01 16:22   ` Eric Blake
2019-10-01 17:01     ` Vladimir Sementsov-Ogievskiy
2019-10-01 16:50   ` Eric Blake
2019-10-01 17:08     ` Eric Blake
2019-10-01 17:15     ` Vladimir Sementsov-Ogievskiy
2019-10-01 15:52 ` [PATCH v4 06/31] python: add commit-per-subsystem.py Vladimir Sementsov-Ogievskiy
2019-10-07 15:55   ` Cornelia Huck
2019-10-07 16:10     ` Vladimir Sementsov-Ogievskiy
2019-10-07 16:16       ` Cornelia Huck
2019-10-07 16:21         ` Daniel P. Berrangé
2019-10-07 17:15           ` Vladimir Sementsov-Ogievskiy
2019-10-01 15:52 ` [PATCH v4 07/31] s390: Fix error_append_hint/error_prepend usage Vladimir Sementsov-Ogievskiy
2019-10-07 15:58   ` Cornelia Huck
2019-10-09  7:42   ` Markus Armbruster
2019-10-11 15:33     ` Vladimir Sementsov-Ogievskiy
2019-10-01 15:52 ` [PATCH v4 08/31] ARM TCG CPUs: " Vladimir Sementsov-Ogievskiy
2019-10-01 15:52 ` [PATCH v4 09/31] PowerPC " Vladimir Sementsov-Ogievskiy
2019-10-01 15:52 ` [PATCH v4 10/31] arm: " Vladimir Sementsov-Ogievskiy
2019-10-01 15:52 ` [PATCH v4 11/31] SmartFusion2: " Vladimir Sementsov-Ogievskiy
2019-10-01 15:53 ` [PATCH v4 12/31] ASPEED BMCs: " Vladimir Sementsov-Ogievskiy
2019-10-01 15:53 ` [PATCH v4 13/31] Boston: " Vladimir Sementsov-Ogievskiy
2019-10-01 15:53 ` [PATCH v4 14/31] PowerNV (Non-Virtualized): " Vladimir Sementsov-Ogievskiy
2019-10-01 15:53 ` [PATCH v4 15/31] PCI: " Vladimir Sementsov-Ogievskiy
2019-10-01 15:53 ` [PATCH v4 16/31] SCSI: " Vladimir Sementsov-Ogievskiy
2019-10-01 15:53 ` [PATCH v4 17/31] USB: " Vladimir Sementsov-Ogievskiy
2019-10-01 15:53 ` [PATCH v4 18/31] VFIO: " Vladimir Sementsov-Ogievskiy
2019-10-01 15:53 ` [PATCH v4 19/31] vhost: " Vladimir Sementsov-Ogievskiy
2019-10-01 15:53 ` [PATCH v4 20/31] virtio: " Vladimir Sementsov-Ogievskiy
2019-10-01 15:53 ` [PATCH v4 21/31] virtio-9p: " Vladimir Sementsov-Ogievskiy
2019-10-02  9:19   ` Greg Kurz
2019-10-02 12:58     ` Vladimir Sementsov-Ogievskiy
2019-10-02 13:11       ` Vladimir Sementsov-Ogievskiy
2019-10-01 15:53 ` [PATCH v4 22/31] XIVE: " Vladimir Sementsov-Ogievskiy
2019-10-01 15:53 ` [PATCH v4 23/31] block: " Vladimir Sementsov-Ogievskiy
2019-10-01 17:09   ` Eric Blake
2019-10-01 18:55     ` Vladimir Sementsov-Ogievskiy
2019-10-01 19:12       ` Vladimir Sementsov-Ogievskiy
2019-10-01 19:44       ` Eric Blake
2019-10-09  7:22   ` Markus Armbruster
2019-10-01 15:53 ` [PATCH v4 24/31] chardev: " Vladimir Sementsov-Ogievskiy
2019-10-01 15:53 ` [PATCH v4 25/31] cmdline: " Vladimir Sementsov-Ogievskiy
2019-10-01 15:53 ` [PATCH v4 26/31] QOM: " Vladimir Sementsov-Ogievskiy
2019-10-01 15:53 ` [PATCH v4 27/31] Migration: " Vladimir Sementsov-Ogievskiy
2019-10-01 15:53 ` [PATCH v4 28/31] Sockets: " Vladimir Sementsov-Ogievskiy
2019-10-01 15:53 ` [PATCH v4 29/31] nbd: " Vladimir Sementsov-Ogievskiy
2019-10-01 17:47   ` Eric Blake
2019-10-01 15:53 ` [PATCH v4 30/31] PVRDMA: " Vladimir Sementsov-Ogievskiy
2019-10-01 15:53 ` [PATCH v4 31/31] ivshmem: " Vladimir Sementsov-Ogievskiy
2019-10-02  3:26 ` [PATCH v4 00/31] error: auto propagated local_err no-reply
2019-10-02 11:58 ` Markus Armbruster
2019-10-08  7:30 ` Markus Armbruster
2019-10-08  8:41   ` Vladimir Sementsov-Ogievskiy
2019-10-08  9:39     ` Greg Kurz
2019-10-08 10:09       ` Vladimir Sementsov-Ogievskiy
2019-10-08 11:59         ` Markus Armbruster
2019-10-09  8:45         ` Vladimir Sementsov-Ogievskiy

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