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 17:23:16

On 01/29/2013 10:36 PM, Eric Niebler wrote:
> On 01/29/2013 09:31 AM, Jeffrey Lee Hellrung, Jr. wrote:
>> On Tue, Jan 29, 2013 at 5:35 AM, Philipp Schwaha  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 don't believe that's the case, Jeff, but I'm not the Phoenix
> implementor. Philipp, I'd suggest you file a bug.
Done.
https://svn.boost.org/trac/boost/ticket/7953

cheers
        Philipp

> 
> Eric
> 
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