https://llvm.org/bugs/show_bug.cgi?id=26899
Bug ID: 26899
Summary: Valarray constructor should have the elements of the
array value-initialized as of C++14 standard, but they
are initialized using a copy constructor.
Product: libc++
Version: 3.8
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: All Bugs
Assignee: unassignedclangb...@nondot.org
Reporter: ionelpopesc...@yahoo.com
CC: llvm-bugs@lists.llvm.org, mclow.li...@gmail.com
Classification: Unclassified
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.
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