[vlc-devel] [PATCH] lib: assert instead of abort

[Steve Lhomme]

On 2019-09-27 16:41, Thomas Guillem wrote:
> 
> 
> On Fri, Sep 27, 2019, at 16:26, Rémi Denis-Courmont wrote:
>> Hi,
>>
>> I am on holidays without laptop, so I cannot check, but I believe the answer to your question is history. I mean, vlc_assert_unreachable() should be used there but it probably did not exist when the code was written.
> 
> I don't like vlc_assert_unreachable(). I would prefer that this helper abort() instead or doing a __builtin_unreachable().
> Indeed,it is very hard to debug a code that reached this statement, everything is UB after that. I prefer to kill the process instead of making the app totally UB.

When compiled in libvlc, vlc_assert_unreachable() asserts. So I think it 
would work like an assert just fine.

On the other hand, unreachable doesn't seem to signal the right issue in 
code called by a libvlc user.

>>
>> Le 20 septembre 2019 15:49:50 GMT+03:00, Romain Vimont <rom1v at videolabs.io> a écrit :
>>> On Fri, Sep 20, 2019 at 03:13:08PM +0300, Rémi Denis-Courmont wrote:
>>>> I completely disagree. When event registration/deregistration fails, you're almost guaranteed a deadlock or some use after free. Much better to abort asap.
>>>
>>> If an assertion fails, then the program has (probably) undefined
>>> behavior.
>>>
>>> But why using assert() everywhere but abort() here? There are a lot of
>>> places where a failing assert() would almost guarantee a deadlock or
>>> some use after free.
>>>
>>>> Le 20 septembre 2019 12:21:37 GMT+03:00, Thomas Guillem <thomas at gllm.fr> a écrit :
>>>>> Because you should not abort in production. Developers will still be
>>>>> notified
>>>>> that they are miss-using the API with the assert.
>>>>>
>>>>> PS: this abort was happening on iOS via VLCKit, the API miss-use had
>>>>> been fixed
>>>>> here: https://code.videolan.org/videolan/VLCKit/merge_requests/19 lib/event.c | 2 +-
>>>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/lib/event.c b/lib/event.c
>>>>> index 28d3d0c232..4a57029b89 100644
>>>>> --- a/lib/event.c
>>>>> +++ b/lib/event.c
>>>>> @@ -179,5 +179,5 @@ void libvlc_event_detach(libvlc_event_manager_t
>>>>> *em, libvlc_event_type_t type,
>>>>>                return;
>>>>>            }
>>>>>       }
>>>>> -    abort();
>>>>> +    assert(!"event not found or already detached");
>>>>>   }
>>>>> -- 
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