<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Jan 22, 2015 at 5:14 PM, Duncan P. N. Exon Smith <span dir="ltr"><<a href="mailto:dexonsmith@apple.com" target="_blank">dexonsmith@apple.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">> On 2015-Jan-22, at 17:11, Duncan P. N. Exon Smith <<a href="mailto:dexonsmith@apple.com">dexonsmith@apple.com</a>> wrote:<br>
><br>
> This tests that `Constructable` was moved, but it still doesn't test<br>
> whether the heap allocation was moved (as opposed to individual<br>
> elements being moved to a new allocation). You need something like<br>
> this to test that:<br>
><br>
> SmallVector<int, 4> V1(8), V2;<br>
> auto First = V1.begin();<br>
> V2 = std::move(V1);<br>
> EXPECT_EQ(First, V2.begin());<br>
<br>
</span>Or maybe you could check that no constructors had been called at all<br>
in the move?<br></blockquote><div><br>This. That's the guarantee I expect from moving a container with dynamic storage - no operations on my elements should be performed at all.<br> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="HOEnZb"><div class="h5"><br>
><br>
> Of course, you only want to check this when you expect the whole<br>
> allocation to move over: when the source vector is in big mode.<br>
><br>
>> On 2015-Jan-22, at 16:43, Lang Hames <<a href="mailto:lhames@gmail.com">lhames@gmail.com</a>> wrote:<br>
>><br>
>> Hi Guys,<br>
>><br>
>> Thanks for catching that - I've attached an updated patch. I'm still just testing correctness, rather than implementation specifics, but it does at least verify that it's move-constructing rather than copy-constructing now.<br>
>><br>
>> Cheers,<br>
>> Lang.<br>
>><br>
>><br>
>> On Thu, Jan 22, 2015 at 4:19 PM, David Blaikie <<a href="mailto:dblaikie@gmail.com">dblaikie@gmail.com</a>> wrote:<br>
>><br>
>><br>
>> On Thu, Jan 22, 2015 at 4:17 PM, Duncan P. N. Exon Smith <<a href="mailto:dexonsmith@apple.com">dexonsmith@apple.com</a>> wrote:<br>
>><br>
>>> On 2015-Jan-22, at 16:04, David Blaikie <<a href="mailto:dblaikie@gmail.com">dblaikie@gmail.com</a>> wrote:<br>
>>><br>
>>> This looks like it's only adding copy, not move - did I miss something?<br>
>>><br>
>>> On Thu, Jan 22, 2015 at 3:54 PM, Lang Hames <<a href="mailto:lhames@gmail.com">lhames@gmail.com</a>> wrote:<br>
>>> Hi All,<br>
>>><br>
>>> The attached patch adds move-construction and move-assignment from SmallVectorImpl<T> to SmallVector<T, N>. It enables us to move between SmallVectors of different types, which will allow me to fix one of the most commented-upon warts from the new JIT APIs.<br>
>>><br>
>>> Unit-test included.<br>
>>><br>
>>> Cheers,<br>
>>> Lang.<br>
>>><br>
>><br>
>> Yeah, the tests don't actually confirm that the thing was moved. In<br>
>> particular, you want to check that whenever the source is in big-mode,<br>
>> the destination points at the same memory that the source used to (well,<br>
>> assuming that's the behaviour you want, which the naive implementation<br>
>> will give you IIUC).<br>
>><br>
>> There's also a "big mode -> small mode" funny state thing that'll happen<br>
>> with the naive implementation. I'm not sure it's *wrong*, but...<br>
>><br>
>> Given:<br>
>><br>
>> SmallVector<int, 1> InBigMode(2);<br>
>> SmallVector<int, 2> InBigModeToo = std::move(InBigMode);<br>
>><br>
>> I think this will pass:<br>
>><br>
>> assert(!InBigModeToo.isSmall());<br>
>><br>
>> This a new state -- a SmallVector can be in "big" mode with a heap<br>
>> allocation, even though its capacity would fit in its "small" mode<br>
>> stack allocation.<br>
>><br>
>> While weird, I don't really have a problem with it (but maybe others<br>
>> do?). Might be worth testing a few operations in this untested state<br>
>> though.<br>
>><br>
>> It's probably valuable that this is the outcome - it'd be wasteful to throw away the dynamic allocation (going down to small mode) - better to keep it even though it's < small_size. So I'd be in favor of this.<br>
>><br>
>><br>
>> <SmallVectorMoveAssignmentFromSmallVectorImpl-2.patch><br>
><br>
><br>
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