Re: [Boost-users] boost_serialization ok with vector<int> but not with vector<int *>

Subject: Re: [Boost-users] boost_serialization ok with vector<int> but not with vector<int *>
From: Robert Ramey (ramey_at_[hidden])
Date: 2015-03-08 20:33:20

Tony Camuso wrote
> On 03/06/2015 07:42 PM, Robert Ramey wrote:
>> Tony Camuso wrote
>>> Why is the compiler okay with ...
>>> 	std::vector
>>> 
> <int>
>>> intvec;
>>>    ... but throws an error for ...
>>> 	std::vector
>>> 
> <int *>
>>> pintvec;
>>
>> The answer can be found here:
>>
>> 

>  &lt;http://&gt;
>> http://stackoverflow.com/questions/19076299/how-do-i-serialize-a-class-containing-pointers-to-primitives
>>
>> I concede that this should be added to the documentation.   Feel free to
>> open a trac item to remind me of this.

actually, I think I can do better than that.  I got in the habit of adding a
layer of static asserts to trap cases where the user breaks some rule or
another.  At the site of the trap, a comment in the code explains what on
has to do to fix it. Of course this is self defense so I don't have
continually answer the same questions over and over. Over the years as I get
a new question, I added traps like this.  For some reason this question
hasn't been asked often enough to trigger my normal behavior.  But I think I
can more or less easily implement this.

>> So the solution is to wrap your int inside a class. This will give it a
>> unique type and distinguish from all the other int instances you don't
>> really want to track.  Also you can use BOOST_SERIALIZATION to create a
>> wrapper.

Note: it's BOOST_SERIALIZATION_STRONG_TYPEDEF.  It's got it's own special
section in the manual.

But it only works for numeric types.

If you want to serialize a string pointer you'll have to snooker your system
like this:
>

Thanks, Robert.

Wasn't aware of the BOOST_SERIALIZATION macro. I'll look it up.

Another question. It seems that attempts to serialize containers of pointers
of any kind throw compiler errors. For example,

std::vector<string> str;  // compiler is ok with serializing this

std::vector<string *> pstr;  // compiler throws an error

The documentation gave me the impression that the serialization lib would
dereference the pointers correctly, and perform all the housekeeping around
that. Also got the impression that nothing special had to be done for the
deserialize step.

That's not correct - this problem occurs for all "primitive types".  Look at
the
documentation on "serialization level".  This basically means all C++
primitive
types + std::string.  To handle std::string use:

> Is my reading comprehension off?  :)

No, but you might want to do more of it.

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