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<base href="https://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - std::vector emplace_back instantiates implicitly-deleted copy constructor"
href="https://llvm.org/bugs/show_bug.cgi?id=27442">27442</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>std::vector emplace_back instantiates implicitly-deleted copy constructor
</td>
</tr>
<tr>
<th>Product</th>
<td>libc++
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>All Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>dexonsmith@apple.com
</td>
</tr>
<tr>
<th>CC</th>
<td>dblaikie@gmail.com, george.burgess.iv@gmail.com, llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=16242" name="attach_16242" title="t.cpp">attachment 16242</a> <a href="attachment.cgi?id=16242&action=edit" title="t.cpp">[details]</a></span>
t.cpp
Using r266855, given:
--
#include <vector>
struct NonCopyable {
NonCopyable(int);
NonCopyable(NonCopyable&&);
};
template <class T> struct Wrapper {
T value;
Wrapper(int value) : value(value) {}
Wrapper(Wrapper &&X) : value(std::move(X.value)) {}
Wrapper(const Wrapper &X) : value(X.value) {}
};
void foo() {
std::vector<Wrapper<NonCopyable>> vector;
vector.emplace_back(5);
}
--
I get the following:
--
$ path/to/clang -nostdinc++ -isystem path/to/libcxx -std=c++11 t.cpp
-fsyntax-only
t.cpp:12:31: error: call to implicitly-deleted copy constructor of
'NonCopyable'
Wrapper(const Wrapper &X) : value(X.value) {}
^ ~~~~~~~
/Users/dexonsmith/data/llvm/llvm.org/projects/libcxx/include/memory:1748:31:
note: in instantiation of member function 'Wrapper<NonCopyable>::Wrapper'
requested here
::new((void*)__p) _Up(_VSTD::forward<_Args>(__args)...);
^
/Users/dexonsmith/data/llvm/llvm.org/projects/libcxx/include/memory:1656:18:
note: in instantiation of function template specialization
'std::__1::allocator<Wrapper<NonCopyable>
>::construct<Wrapper<NonCopyable>, const Wrapper<NonCopyable> &>'
requested here
{__a.construct(__p, _VSTD::forward<_Args>(__args)...);}
^
/Users/dexonsmith/data/llvm/llvm.org/projects/libcxx/include/memory:1502:14:
note: in instantiation of function template specialization
'std::__1::allocator_traits<std::__1::allocator<Wrapper<NonCopyable> >
<span class="quote">>::__construct<Wrapper<NonCopyable>, const Wrapper<NonCopyable> &>' requested</span >
here
{__construct(__has_construct<allocator_type, _Tp*, _Args...>(),
^
/Users/dexonsmith/data/llvm/llvm.org/projects/libcxx/include/memory:1618:17:
note: in instantiation of function template specialization
'std::__1::allocator_traits<std::__1::allocator<Wrapper<NonCopyable> >
<span class="quote">>::construct<Wrapper<NonCopyable>, const Wrapper<NonCopyable> &>' requested</span >
here
construct(__a, _VSTD::__to_raw_pointer(__end2-1),
_VSTD::move_if_noexcept(*--__end1));
^
/Users/dexonsmith/data/llvm/llvm.org/projects/libcxx/include/vector:892:21:
note: in instantiation of function template specialization
'std::__1::allocator_traits<std::__1::allocator<Wrapper<NonCopyable> >
<span class="quote">>::__construct_backward<Wrapper<NonCopyable> *>' requested here</span >
__alloc_traits::__construct_backward(this->__alloc(), this->__begin_,
this->__end_, __v.__begin_);
^
/Users/dexonsmith/data/llvm/llvm.org/projects/libcxx/include/vector:1629:5:
note: in instantiation of member function
'std::__1::vector<Wrapper<NonCopyable>,
std::__1::allocator<Wrapper<NonCopyable> > >::__swap_out_circular_buffer'
requested here
__swap_out_circular_buffer(__v);
^
/Users/dexonsmith/data/llvm/llvm.org/projects/libcxx/include/vector:1648:9:
note: in instantiation of function template specialization
'std::__1::vector<Wrapper<NonCopyable>,
std::__1::allocator<Wrapper<NonCopyable> >
<span class="quote">>::__emplace_back_slow_path<int>' requested here</span >
__emplace_back_slow_path(_VSTD::forward<_Args>(__args)...);
^
t.cpp:17:10: note: in instantiation of function template specialization
'std::__1::vector<Wrapper<NonCopyable>,
std::__1::allocator<Wrapper<NonCopyable> > >::emplace_back<int>' requested here
vector.emplace_back(5);
^
t.cpp:5:3: note: copy constructor is implicitly deleted because 'NonCopyable'
has a user-declared move constructor
NonCopyable(NonCopyable&&);
^
1 error generated.
--
Commenting out `Wrapper(const Wrapper &X)` will let it compile. It's not clear
why having the extra (implicitly deleted) constructor around causes
emplace_back to fail to compile.
This compile error scared me enough that I committed r266909 to stop using
std::vector on types that are expensive to copy.</pre>
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