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

Subject: Re: [Boost-users] [phoenix] segmentation fault with valarray
From: Philipp Schwaha (philipp_at_[hidden])
Date: 2013-01-30 17:22:54

hi Jeff!

On 01/29/2013 06:31 PM, Jeffrey Lee Hellrung, Jr. wrote:
> On Tue, Jan 29, 2013 at 5:35 AM, Philipp Schwaha <philipp_at_[hidden]
> <mailto: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.
I have also tried inserting a number instead of the val(mass), it still
results in a segfault.
thanks for taking the time to have a look!

cheers
        Philipp

> 
> - Jeff
> 
> 
> 
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