Nothrow functions

[Janderson]

Janderson wrote:
> Andrei Alexandrescu wrote:
>> Janderson wrote:
>>> Andrei Alexandrescu wrote:
>>>> dsimcha wrote:
>>>>> == Quote from Janderson (ask at me.com)'s article
>>>>>> Walter Bright wrote:
>>>>> http://www.reddit.com/r/programming/comments/74fx4/nothrow_functions_in_the_d_programming_language/ 
>>>>>
>>>>>> Perhaps now constructors can enforce no-throw.  Functions that have
>>>>>> throw would have to be handled in that constructor.  Of course we 
>>>>>> could
>>>>>> always do this manually, but it might be worth considering making 
>>>>>> on by
>>>>>> default for constructors.
>>>>>> -Joel
>>>>>
>>>>> Please, please, please, please, *please* no!!!  Anything that is in 
>>>>> any way
>>>>> similar to checked exception Hell in Java does not belong in D.  
>>>>> Nothrow is a
>>>>> great feature precisely because, by being a contract that is only 
>>>>> enforced when
>>>>> the programmer explicitly asks for it to be, it can be simply 
>>>>> ignored in places
>>>>> where one doesn't want to use it.  Making nothrow the default in 
>>>>> constructors
>>>>> really smacks of Java-style bondage and discipline, and a major 
>>>>> reason why I use D
>>>>> is to avoid such things.  If nothrow is the default *anywhere*, it 
>>>>> will lead to
>>>>> aggravation and error swallowing similar to Java's checked exceptions.
>>>>
>>>> I agree. Bondage and discipline, heh :o). I'm actually surprised at 
>>>> the desire of making most constructors nothrow. Why?
>>>>
>>>> Andrei
>>>
>>> If an exception fires during the construction of an object and you 
>>> don't handle it your left with a partially formed object.  It becomes 
>>> difficult to then make that object an invariant.  This is 
>>> particularly bad when it occurs in the base classes constructor.
>>
>> But C++ solved this by making it impossible to obtain a 
>> partially-constructed object. If the constructor throws, there's never 
>> an object to talk about.
>>
>> Andrei
> 
> That's a good point, I guess the issue I've had in the past is with 
> resource handles and dangling pointers.
> 
> What if the object creates a handle to a resource in the constructor 
> just before the exception.  That resource never gets cleaned up unless 
> your explicitly handle it with a try-catch.  Other then the out of 
> memory one, I'm not aware of any C++ standard library that throw in the 
> constructor.
> 
> -Joel

Maybe there should be some sort of way to detect handles that are not 
RAII handled in the constructor?

-Joel