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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Union with variant member with non-trivial default constructor but another variant member has a default member initializer with deleted default constructor"
href="https://bugs.llvm.org/show_bug.cgi?id=39686">39686</a>
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<th>Summary</th>
<td>Union with variant member with non-trivial default constructor but another variant member has a default member initializer with deleted default constructor
</td>
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>C++14
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>yaghmour.shafik@gmail.com
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<th>CC</th>
<td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>Given the following code which is a more minimal example taken from this
Stackoveflow question <a href="https://stackoverflow.com/q/53310690/1708801">https://stackoverflow.com/q/53310690/1708801</a>
struct X {
X() {} //non-trivial default constructor
};
union U {
X x;
int i{}; //default member initializer
};
void foo() {
U u;
}
clang gives the following diagnostic <a href="https://godbolt.org/z/6oTJ01">https://godbolt.org/z/6oTJ01</a> :
call to implicitly-deleted default constructor of 'U'
U u;
^
note: default constructor of 'U' is implicitly deleted because variant field
'x' has a non-trivial default constructor
X x;
^
but [class.default.ctor]p2 <a href="http://eel.is/c++draft/class.default.ctor#2.1">http://eel.is/c++draft/class.default.ctor#2.1</a> says:
A defaulted default constructor for class X is defined as deleted if:
- X is a union that has a variant member with a non-trivial default
constructor and no variant member of X has a default member initializer,
U does have a member with a default member initializer so the default
constructor should not be deleted and this should be well-formed.</pre>
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