deprecated delete and manual memory management

[Daniel Gibson]

Am 27.04.2011 02:26, schrieb Steven Schveighoffer:
> On Tue, 26 Apr 2011 20:15:45 -0400, Daniel Gibson
> <metalcaedes at gmail.com> wrote:
> 
>> Am 27.04.2011 02:03, schrieb Steven Schveighoffer:
>>> On Tue, 26 Apr 2011 19:45:21 -0400, Daniel Gibson
>>> <metalcaedes at gmail.com> wrote:
>>>
>>>> I just noticed something regarding clear():
>>>>   struct Bar { ... }
>>>>   Bar *b = new Bar();
>>>> This compiles without any warning, but doesn't call the destructor:
>>>>   clear(b);
>>>> This compiles without any warning and actually does what you'd expect,
>>>> i.e. calls destructor:
>>>>   clear(*b);
>>>>
>>>> Is this behavior expected/wanted? If not: Is it a known bug? I couldn't
>>>> find it in the bugtracker, but maybe I searched for the wrong keywords.
>>>
>>> Let's start with class references.  Because class references cannot be
>>> separated from its reference, you have to finalize the class when
>>> finalizing the reference, because there's no way to say "clear what this
>>> reference refers to" vs. "clear this reference".  So you have to give a
>>> way to finalize a class instance.
>>>
>>> With pointers, however, you can specify as you say, whether you want to
>>> clear the pointer or the struct itself.
>>>
>>> Now, is it much useful to clear a pointer without clearing what it
>>> points to?  I'd say no, clearing a pointer is as easy as doing ptr =
>>> null.  So I'm thinking, it should be filed as a bug.
>>>
>>> The obvious thing to decide is, what should be done on references to
>>> references?  If you clear a double pointer, should it go through both
>>> pointers?  Or a pointer to a class reference?
>>>
>>> I'd say no, but you have to take extra steps to ensure it is this way.
>>>
>>> -Steve
>>
>> IMHO clear isn't needed for anything but structs and Objects.
>> For any simple type or pointer you can just write x = x.init; instead of
>> clear(x) or, as you already mentioned, x=null; for pointers.
> 
> It is useful for it to work for generic code.
> 
>> AFAIK the main purpose of clear() is to explicitly call the destructor -
>> and that only makes sense for structs and classes.
>> Allowing it for other types (especially pointers) just sneaks in
>> non-obvious bugs, especially when it's considered a replacement for
>> delete (which calls the destructor for both Object a *struct).
> 
> I'm not sure it introduces subtle bugs for things besides pointers. 
> Clearing an int should be harmless.
> 
>> BTW: clear() has often been mentioned in this NG but isn't documented in
>> the Phobos documentation (which is no surprise because clear() doesn't
>> have doc-comments).
>>
>> So I guess I'll report this as a bug.
> 
> If you mean that clear has no docs, I already reported that.
> 
> http://d.puremagic.com/issues/show_bug.cgi?id=5855
> 
> Feel free to report the enhancement request for clear to dereference
> pointers.
> 
> -Steve

Done: http://d.puremagic.com/issues/show_bug.cgi?id=5895