[phobos] swap()

[Andrei Alexandrescu]

I'm not sure I understand where the brokenness is. Could you please post 
to http://d.puremagic.com/issues/show_bug.cgi?id=4789 an example that 
does break even after David Simcha's fix 
(http://dsource.org/projects/phobos/changeset/1948)?

Andrei

On 1/2/11 9:19 AM, Martin Nowak wrote:
> Well, bug 4789 is fixed for static arrays but reintroduced for structs
> with elaborate assign.
> Array copy is not allowed for overlapping memory.
>
> ubyte[T.sizeof] t = void;
> auto a = (cast(ubyte*) &lhs)[0 .. T.sizeof];
> auto b = (cast(ubyte*) &rhs)[0 .. T.sizeof];
> t[] = a[];
> a[] = b[]; <-- will raise exception
> b[] = t[];
>
> Martin
>
> On Sun, 02 Jan 2011 00:42:44 +0100, Andrei Alexandrescu
> <andrei at erdani.com> wrote:
>
>> This has been lying in my inbox for a good while. I see now the bug is
>> fixed. Any trailing questions regarding it?
>>
>> Andrei
>>
>> On 9/2/10 10:58 PM, David Simcha wrote:
>>> A few questions about std.algorithm.swap() that came up when I was
>>> reading the code to fix Bug 4789:
>>>
>>> 1. Do we really need to use memcpy() for structs w/o a postblit? I can't
>>> see any advantages and it seems like it might be less efficient, since
>>> for a struct without a postblit just using plain old assignment should
>>> be about as efficient as it gets.
>>>
>>> 2. memcpy() isn't guaranteed to work for overlapping memory blocks.
>>> Shouldn't there be a check in to make sure a and b don't have the same
>>> address?
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