Re: [Qemu-devel] [PATCH RFC 0/3] error: allow local errors to trigger abort

[John Snow]

On 06/17/2015 10:29 AM, Kevin Wolf wrote:
> Am 17.06.2015 um 16:26 hat John Snow geschrieben:
>>
>>
>> On 06/16/2015 08:53 AM, Michael S. Tsirkin wrote:
>>>     
>>>     It's a common idiom:
>>>     
>>>         Error *local_err = NULL;
>>>         ....
>>>         foo(&local_err);
>>>         ...
>>>         if (local_err) {
>>>             error_propagate(errp, local_err);
>>>             return;
>>>         }
>>>     
>>>     Unfortunately it means that call to foo(&local_err) will
>>>     not abort even if errp is set to error_abort.
>>>     
>>>     Instead, we get an abort at error_propagate which is too late.
>>>     
>>
>> Please humor the ignorant: Why is this too late? Any code that does
>> anything between foo(&local_err) and error_propagate is already broken.
> 
> The interesting part is the stack trace which is truncated if you
> abort() only in the outermost caller.
> 
> Kevin
> 

AHHH, that makes sense now, thank you.

>>>     To fix, add an API to check errp and set local_err to error_abort
>>>     if errp is error_abort.
>>>
>>> Michael S. Tsirkin (3):
>>>   error: don't rely on pointer comparisons
>>>   error: allow local errors to trigger abort
>>>   block/nfs: switch to error_init_local
>>>
>>>  include/qapi/error.h |  5 +++++
>>>  block/nfs.c          |  2 +-
>>>  util/error.c         | 21 ++++++++++++++++-----
>>>  3 files changed, 22 insertions(+), 6 deletions(-)
>>>