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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Valarray constructor should have the elements of the array value-initialized as of C++14 standard, but they are initialized using a copy constructor."
href="https://llvm.org/bugs/show_bug.cgi?id=26899">26899</a>
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<th>Summary</th>
<td>Valarray constructor should have the elements of the array value-initialized as of C++14 standard, but they are initialized using a copy constructor.
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<th>Product</th>
<td>libc++
</td>
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<th>Version</th>
<td>3.8
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>All Bugs
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>ionelpopescu97@yahoo.com
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
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<th>Classification</th>
<td>Unclassified
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<pre>The behavior of the valarray constructor is different from the decription in
the c++14 standard. It says that the elements of the array are
value-initialized but the instead just only one element is value-initialized
and the rest are initialized using a copy constructor.
Decription in the c++14 standard:
explicit valarray(size_t);
2 The array created by this constructor has a length equal to the value of the
argument. The elements of the array are value-initialized
Example:
#include <stdio.h>
#include <valarray>
int id =0;
struct Foo {
Foo()
{
printf("Spawn Foo ID %d \n", id++);
}
};
int main()
{
std::valarray<Foo> x(5);
}
Results:
If we use Intel compiler (Icc 2016) or VS2015, gcc 4.9.2
Spawn Foo ID 0
Spawn Foo ID 1
Spawn Foo ID 2
Spawn Foo ID 3
Spawn Foo ID 4
If we use clang++ and libc++
We get the following output
Spawn Foo ID 0
Spawn Foo ID 1
There are only two appearances because the copy constructor is called instead
of the default constructor as it should be for value initialization.</pre>
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