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Re: [Qemu-devel] [PATCH RFC v2 29/47] qapi: Replace dirty is_c_ptr() by
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH RFC v2 29/47] qapi: Replace dirty is_c_ptr() by method c_null() |
Date: |
Thu, 30 Jul 2015 08:19:28 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 |
On 07/29/2015 11:22 AM, Markus Armbruster wrote:
> Eric Blake <address@hidden> writes:
>
>> On 07/29/2015 02:32 AM, Markus Armbruster wrote:
>>
>>>>> 2. We can leak retval only when qmp_FOO() returns non-null and local_err
>>>>> is non-null. This must not happen, because:
>>>>>
>>>>> a. local_err must be null before the call, and
>>>>>
>>>>> b. the call must not return non-null when it sets local_err.
>>>>
>>>> We don't state that contract anywhere, but I doubt any of the qmp_FOO()
>>>> functions violate it, so it is worth making it part of the contract.
>>>
>>> It's a general Error API rule: set an error exactly on failure. It
>>> applies to any function returning errors through an Error **errp
>>> parameter, and we generally don't bother to spell it out for the
>>> individual functions.
>>>
>>> The part that needs to be spelling out is what success and failure mean.
>>> A qmp_FOO() returning an object returns null on failure.
For qmp_FOO(), this is a reasonable contract. But our very own
generated code does not follow these rules: visit_type_FOO() can assign
into *obj even when setting an error, if it encounters a parse error
halfway through the struct, leaving the caller responsible to still
clean up the mess if it wants to avoid a memory leak.
Maybe that means our generated code needs to be reworked to properly
clean up on a failed parse, such that *obj is guaranteed to be NULL if
an error is returned. As a separate patch, of course.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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- [Qemu-devel] [PATCH RFC v2 06/47] qapi: Drop unused and useless parameters and variables, (continued)
- [Qemu-devel] [PATCH RFC v2 06/47] qapi: Drop unused and useless parameters and variables, Markus Armbruster, 2015/07/01
- [Qemu-devel] [PATCH RFC v2 29/47] qapi: Replace dirty is_c_ptr() by method c_null(), Markus Armbruster, 2015/07/01
- Re: [Qemu-devel] [PATCH RFC v2 29/47] qapi: Replace dirty is_c_ptr() by method c_null(), Eric Blake, 2015/07/22
- Re: [Qemu-devel] [PATCH RFC v2 29/47] qapi: Replace dirty is_c_ptr() by method c_null(), Markus Armbruster, 2015/07/28
- Re: [Qemu-devel] [PATCH RFC v2 29/47] qapi: Replace dirty is_c_ptr() by method c_null(), Eric Blake, 2015/07/28
- Re: [Qemu-devel] [PATCH RFC v2 29/47] qapi: Replace dirty is_c_ptr() by method c_null(), Markus Armbruster, 2015/07/29
- Re: [Qemu-devel] [PATCH RFC v2 29/47] qapi: Replace dirty is_c_ptr() by method c_null(), Eric Blake, 2015/07/29
- Re: [Qemu-devel] [PATCH RFC v2 29/47] qapi: Replace dirty is_c_ptr() by method c_null(), Markus Armbruster, 2015/07/29
- Re: [Qemu-devel] [PATCH RFC v2 29/47] qapi: Replace dirty is_c_ptr() by method c_null(),
Eric Blake <=
- Re: [Qemu-devel] [PATCH RFC v2 29/47] qapi: Replace dirty is_c_ptr() by method c_null(), Markus Armbruster, 2015/07/30
- Re: [Qemu-devel] [PATCH RFC v2 29/47] qapi: Replace dirty is_c_ptr() by method c_null(), Eric Blake, 2015/07/30
- Re: [Qemu-devel] [PATCH RFC v2 29/47] qapi: Replace dirty is_c_ptr() by method c_null(), Markus Armbruster, 2015/07/31
Re: [Qemu-devel] [PATCH RFC v2 29/47] qapi: Replace dirty is_c_ptr() by method c_null(), Eric Blake, 2015/07/23
[Qemu-devel] [PATCH RFC v2 23/47] qapi: New QAPISchemaVisitor, Markus Armbruster, 2015/07/01
[Qemu-devel] [PATCH RFC v2 31/47] qapi-event: Eliminate global variable event_enum_value, Markus Armbruster, 2015/07/01
[Qemu-devel] [PATCH RFC v2 22/47] qapi: QAPISchema code generation helper methods, Markus Armbruster, 2015/07/01