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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - clang++ miscompilation while generating copy constructors of classes containing 0-length array"
href="https://bugs.llvm.org/show_bug.cgi?id=40682">40682</a>
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<th>Summary</th>
<td>clang++ miscompilation while generating copy constructors of classes containing 0-length array
</td>
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<th>Product</th>
<td>clang
</td>
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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
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>C++
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>joran.bigalet@gmail.com
</td>
</tr>
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<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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<p>
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<pre>The auto-generated copy constructor of a struct containing a 0-length array
followed by exactly 1 trivially copyable field will not copy the later.
This holds for copy assignments.
Here is a simple example:
===================================================
#include <cstdio>
struct NonTrivial {
int n;
NonTrivial& operator=(NonTrivial o) {
this->n = o.n;
return *this;
}
};
struct S {
NonTrivial _a; // to force clang to generate a copy assignment constructor
int ok; // not mandatory, only to show other trivial fields are still
copied
int _b[0];
int bugged; // not copied by the auto-generated copy assignment
constructor, unless directly followed by another non-trivial field
};
int main() {
S foo;
foo.ok = 11;
foo.bugged = 22;
S bar;
bar.ok = 9876;
bar.bugged = 4321;
bar = foo;
printf("%d %d ; %d %d\n", foo.ok, foo.bugged, bar.ok, bar.bugged);
// expected: 11 22 ; 11 22
// output: 11 22 ; 11 4321
return 0;
}
===================================================</pre>
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