[PATCH] D48342: [libcxx] Optimize vectors construction of trivial types from an iterator range with const-ness mismatch.

[Arthur O'Dwyer via Phabricator via cfe-commits]

Quuxplusone added inline comments.


================
Comment at: libcxx/test/std/containers/sequences/vector/vector.cons/construct_iter_iter.pass.cpp:161
+  {
+    // Though types are different, initialization can be done with `memcpy`.
+    int32_t array[1] = {-1};
----------------
vsapsai wrote:
> Quuxplusone wrote:
> > I might add "can be, but currently isn't, done with memcpy."
> > 
> > Here's my other suggested test:
> > 
> > ```
> > struct X { int x; };
> > struct Y { int y; };
> > struct Z : X, Y { int z; };
> > {
> >     Z z;
> >     Z *array[1] = { &z };
> >     // Though the types Z* and Y* are very similar, initialization still cannot be done with memcpy.
> >     std::vector<Y*> v(array, array + 1);
> >     assert(v[0] == &z);
> > }
> > ```
> Thanks, I'll try your `XYZ` test, looks like it should help with my `iostream*/ostream*` struggles.
LGTM! Ship it!
(I'm surprised the structs can be defined inside the body of `main()` like that, but I have no objection to doing so.)


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  https://reviews.llvm.org/D48342/new/

https://reviews.llvm.org/D48342