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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Diagnostic withholds number of line responsible for bad template instantiation"
href="https://bugs.llvm.org/show_bug.cgi?id=46000">46000</a>
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<th>Summary</th>
<td>Diagnostic withholds number of line responsible for bad template instantiation
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>C++
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>tonyelewis@hotmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<pre>This code has a function template that wraps emplace_back() for vector<int> and
then code that erroneously attempts to instantiate it to emplace_back a
nullptr:
#include <vector>
template <typename... Ts>
decltype(auto) int_vec_emplace_back_wrapper(std::vector<int> &vec, Ts
&&...values) {
return vec.emplace_back(std::forward<Ts>(values)...);
}
void f(std::vector<int> &vec) {
int_vec_emplace_back_wrapper(vec, nullptr);
}
GCC's diagnostic includes a mention the erroneous line 9 but Clang's diagnostic
doesn't:
In file included from a.cpp:1:
In file included from
/usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/c++/8/vector:61:
In file included from
/usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/c++/8/bits/allocator.h:46:
In file included from
/usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/x86_64-linux-gnu/c++/8/bits/c++allocator.h:33:
/usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/c++/8/ext/new_allocator.h:136:23:
error: cannot initialize a new value of type 'int' with an rvalue of type
'nullptr_t'
{ ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/c++/8/bits/alloc_traits.h:475:8:
note: in instantiation of function template specialization
'__gnu_cxx::new_allocator<int>::construct<int, nullptr_t>' requested here
{ __a.construct(__p, std::forward<_Args>(__args)...); }
^
/usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/c++/8/bits/vector.tcc:103:21:
note: in instantiation of function template specialization
'std::allocator_traits<std::allocator<int> >::construct<int, nullptr_t>'
requested here
_Alloc_traits::construct(this->_M_impl, this->_M_impl._M_finish,
^
a.cpp:5:14: note: in instantiation of function template specialization
'std::vector<int, std::allocator<int> >::emplace_back<nullptr_t>' requested
here
return vec.emplace_back(std::forward<Ts>(values)...);
^
1 error generated.
(Removing int_vec_emplace_back_wrapper()'s variadicity doesn't improve the
diagnostic but giving it an explicit void return type does)
<a class="bz_bug_link
bz_status_NEW "
title="NEW - Diagnostic doesn't include interesting template instantiation location"
href="show_bug.cgi?id=20452">https://bugs.llvm.org/show_bug.cgi?id=20452</a> touches similar issues but I don't
believe it subsumes this.</pre>
</div>
</p>
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