Aliasing bug in std::valarray

[Bastian Pranzas <bastian at moduleworks dot com>]

Hi,

std::valarray seems to show behaviour that I find at least unexpected 
and think it might be a bug. Sample code:

#include <valarray>
#include <cstdio>

int main()
{
    std::valarray<int> a {1, 1};
    std::valarray<int> b {1, 1};
    a -= b * a[0];
    std::printf("%d\n", a[1]);
    return 0;
}

The a[1] will still be 1 after the subtract, because a[0] will be set to 
0 and then the 0 will be used for the second multiply. My expectation 
from that code is that a[0] should be a fixed value throughout the whole 
calculation.

Regards

--
Bastian Pranzas
ModuleWorks GmbH