Re: [Boost-users] [phoenix] segmentation fault with valarray

Subject: Re: [Boost-users] [phoenix] segmentation fault with valarray
From: Jeffrey Lee Hellrung, Jr. (jeffrey.hellrung_at_[hidden])
Date: 2013-01-29 12:31:36

On Tue, Jan 29, 2013 at 5:35 AM, Philipp Schwaha <philipp_at_[hidden]>wrote:

> Hi all!
>
> I have worked with phoenix together with valarray and am currently
> stumbling over a case of segmentation fault.
>
> I construct the following phoenix expression
>
> boost::phoenix::at_c<0>(arg1) += boost::phoenix::at_c<1>(arg1) /
> val(mass) * arg2
>
> I then feed a std::tuple<std::valarray<double>, std::valarray<double>>
> to it. It compiles nicely with gcc (4.6 & 4.7) using boost 1.52 as well
> as trunk. The resulting executable then proceeds to segfault, however. I
> have put together a small example (c++11) demonstrating my problem.
>
> The valarray's memory should already be reserved from original
> initialization. Performing the same operations manually with just the
> valarray not in phoenix seems to work fine.
> Am I missing something or doing something stupid here?
>
> thanks for any help!
>
> cheers
>         Philipp
>

I don't know the internals of Phoenix intimately, but it *might* hold
subexpressions by reference rather than by value, implying that you'd have
dangling references when grabbing "mass" upon applying your Phoenix
function object. Just a guess if you wanted something to look into until
someone more knowledgeable replies.

- Jeff